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  Subjects -> METEOROLOGY (Total: 112 journals)
Showing 1 - 36 of 36 Journals sorted by number of followers
Journal of Atmospheric and Solar-Terrestrial Physics     Hybrid Journal   (Followers: 198)
Nature Climate Change     Full-text available via subscription   (Followers: 134)
Journal of the Atmospheric Sciences     Hybrid Journal   (Followers: 81)
Atmospheric Environment     Hybrid Journal   (Followers: 73)
Atmospheric Research     Hybrid Journal   (Followers: 69)
Climatic Change     Open Access   (Followers: 66)
Journal of Climate     Hybrid Journal   (Followers: 54)
Bulletin of the American Meteorological Society     Open Access   (Followers: 51)
Atmospheric Chemistry and Physics (ACP)     Open Access   (Followers: 48)
Climate Policy     Hybrid Journal   (Followers: 44)
Climate Dynamics     Hybrid Journal   (Followers: 44)
Advances in Atmospheric Sciences     Hybrid Journal   (Followers: 43)
Nature Reports Climate Change     Full-text available via subscription   (Followers: 37)
Atmospheric Science Letters     Open Access   (Followers: 36)
Journal of Applied Meteorology and Climatology     Hybrid Journal   (Followers: 35)
Journal of Atmospheric and Oceanic Technology     Hybrid Journal   (Followers: 34)
Monthly Weather Review     Hybrid Journal   (Followers: 34)
International Journal of Climatology     Hybrid Journal   (Followers: 31)
American Journal of Climate Change     Open Access   (Followers: 31)
Advances in Climate Change Research     Open Access   (Followers: 31)
Boundary-Layer Meteorology     Hybrid Journal   (Followers: 31)
Journal of Hydrology and Meteorology     Open Access   (Followers: 29)
Developments in Atmospheric Science     Full-text available via subscription   (Followers: 28)
Weather and Forecasting     Hybrid Journal   (Followers: 28)
The Quarterly Journal of the Royal Meteorological Society     Hybrid Journal   (Followers: 27)
Journal of Space Weather and Space Climate     Open Access   (Followers: 27)
Climate Change Economics     Hybrid Journal   (Followers: 26)
Atmosphere     Open Access   (Followers: 26)
Meteorology and Atmospheric Physics     Hybrid Journal   (Followers: 26)
Space Weather     Full-text available via subscription   (Followers: 25)
Advances in Meteorology     Open Access   (Followers: 24)
Energy & Environment     Hybrid Journal   (Followers: 24)
International Journal of Atmospheric Sciences     Open Access   (Followers: 22)
Tellus A     Open Access   (Followers: 22)
International Journal of Climate Change Strategies and Management     Hybrid Journal   (Followers: 22)
Journal of Atmospheric Chemistry     Hybrid Journal   (Followers: 21)
Tellus B     Open Access   (Followers: 21)
Dynamics of Atmospheres and Oceans     Hybrid Journal   (Followers: 19)
Weather     Hybrid Journal   (Followers: 19)
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 18)
Global Meteorology     Open Access   (Followers: 17)
Weather and Climate Extremes     Open Access   (Followers: 16)
Atmosphere-Ocean     Full-text available via subscription   (Followers: 15)
Atmospheric Chemistry and Physics Discussions (ACPD)     Open Access   (Followers: 15)
Journal of Meteorology and Climate Science     Full-text available via subscription   (Followers: 14)
Theoretical and Applied Climatology     Hybrid Journal   (Followers: 13)
Climate Resilience and Sustainability     Open Access   (Followers: 13)
Monthly Notices of the Royal Astronomical Society     Hybrid Journal   (Followers: 13)
Climate Change Responses     Open Access   (Followers: 12)
Atmospheric and Oceanic Science Letters     Open Access   (Followers: 11)
Journal of Hydrometeorology     Hybrid Journal   (Followers: 11)
Environmental Dynamics and Global Climate Change     Open Access   (Followers: 8)
Current Climate Change Reports     Hybrid Journal   (Followers: 8)
Climate Change Research Letters     Open Access   (Followers: 7)
Advances in Statistical Climatology, Meteorology and Oceanography     Open Access   (Followers: 7)
Climate     Open Access   (Followers: 6)
Open Journal of Modern Hydrology     Open Access   (Followers: 6)
Climate Risk Management     Open Access   (Followers: 6)
Mathematics of Climate and Weather Forecasting     Open Access   (Followers: 6)
Aeolian Research     Hybrid Journal   (Followers: 6)
Climate Research     Hybrid Journal   (Followers: 6)
Journal of the Meteorological Society of Japan     Partially Free   (Followers: 6)
Change and Adaptation in Socio-Ecological Systems     Open Access   (Followers: 5)
The Cryosphere (TC)     Open Access   (Followers: 5)
Dynamics and Statistics of the Climate System     Open Access   (Followers: 5)
International Journal of Environment and Climate Change     Open Access   (Followers: 5)
Climate of the Past (CP)     Open Access   (Followers: 5)
Urban Climate     Hybrid Journal   (Followers: 4)
Environmental and Climate Technologies     Open Access   (Followers: 4)
Climate and Energy     Full-text available via subscription   (Followers: 4)
The Cryosphere Discussions (TCD)     Open Access   (Followers: 4)
Carbon Balance and Management     Open Access   (Followers: 4)
Weatherwise     Hybrid Journal   (Followers: 4)
Meteorological Applications     Hybrid Journal   (Followers: 4)
Journal of Integrative Environmental Sciences     Hybrid Journal   (Followers: 4)
Russian Meteorology and Hydrology     Hybrid Journal   (Followers: 3)
Meteorologische Zeitschrift     Full-text available via subscription   (Followers: 3)
npj Climate and Atmospheric Science     Open Access   (Followers: 3)
Atmospheric Environment : X     Open Access   (Followers: 3)
Journal of Climate Change     Full-text available via subscription   (Followers: 3)
Acta Meteorologica Sinica     Hybrid Journal   (Followers: 3)
Economics of Disasters and Climate Change     Hybrid Journal   (Followers: 3)
Frontiers in Climate     Open Access   (Followers: 3)
Ciencia, Ambiente y Clima     Open Access   (Followers: 3)
Journal of Climatology     Open Access   (Followers: 3)
Atmósfera     Open Access   (Followers: 3)
Climate Services     Open Access   (Followers: 3)
Open Atmospheric Science Journal     Open Access   (Followers: 2)
GeoHazards     Open Access   (Followers: 2)
Journal of Weather Modification     Full-text available via subscription   (Followers: 2)
Meteorological Monographs     Hybrid Journal   (Followers: 2)
International Journal of Image and Data Fusion     Hybrid Journal   (Followers: 2)
Meteorologica     Open Access   (Followers: 2)
Climate Summary of South Africa     Full-text available via subscription   (Followers: 2)
气候与环境研究     Full-text available via subscription   (Followers: 1)
Journal of Meteorological Research     Full-text available via subscription   (Followers: 1)
Bulletin of Atmospheric Science and Technology     Hybrid Journal   (Followers: 1)
Michigan Journal of Sustainability     Open Access   (Followers: 1)
Tropical Cyclone Research and Review     Open Access   (Followers: 1)
International Journal of Biometeorology     Hybrid Journal   (Followers: 1)
Modeling Earth Systems and Environment     Hybrid Journal   (Followers: 1)
Mediterranean Marine Science     Open Access   (Followers: 1)
Large Marine Ecosystems     Full-text available via subscription   (Followers: 1)
Weather and Climate Dynamics     Open Access  
Journal of Agricultural Meteorology     Open Access  
Nīvār     Open Access  
Revista Iberoamericana de Bioeconomía y Cambio Climático     Open Access  
Mètode Science Studies Journal : Annual Review     Open Access  
Earth Perspectives - Transdisciplinarity Enabled     Open Access  
Climate of the Past Discussions (CPD)     Open Access  
Revista Brasileira de Meteorologia     Open Access  
Studia Geophysica et Geodaetica     Hybrid Journal  

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Similar Journals
Journal Cover
Monthly Notices of the Royal Astronomical Society
Journal Prestige (SJR): 2.346
Citation Impact (citeScore): 4
Number of Followers: 13  
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0035-8711 - ISSN (Online) 1365-2966
Published by Oxford University Press Homepage  [416 journals]
  • Systematic uncertainties in models of the cosmic dawn
    • Authors: Mirocha J; Lamarre H, Liu A.
      Pages: 1555 - 1564
      Abstract: ABSTRACTModels of the reionization and reheating of the intergalactic medium (IGM) at redshifts z ≳ 6 continue to grow more sophisticated in anticipation of near-future 21-cm, cosmic microwave background, and galaxy survey measurements. However, there are many potential sources of systematic uncertainty in models that could bias and/or degrade upcoming constraints if left unaccounted for. In this work, we examine three commonly ignored sources of uncertainty in models for the mean reionization and thermal histories of the IGM: the underlying cosmology, halo mass function (HMF), and choice of stellar population synthesis (SPS) model. We find that cosmological uncertainties affect the Thomson scattering optical depth at the few per cent level and the amplitude of the global 21-cm signal at the ∼5–10 mK level. The differences brought about by choice of HMF and SPS models are more dramatic, comparable to the 1σ error bar on τe and an ∼20 mK effect on the global 21-cm signal amplitude. Finally, we jointly fit galaxy luminosity functions and global 21-cm signals for all HMF/SPS combinations and find that (i) doing so requires additional free parameters to compensate for modelling systematics and (ii) the spread in constraints on parameters of interest for different HMF and SPS choices, assuming 5 mK noise in the global signal, is comparable to those obtained when adopting the 'true' HMF and SPS with ≳20 mK errors. Our work highlights the need for dedicated efforts to reduce modelling uncertainties in order to enable precision inference with future data sets.
      PubDate: Mon, 05 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab949
      Issue No: Vol. 504, No. 2 (2021)
  • Atomistic simulations of the free-energy landscapes of interstellar
           chemical reactions: the case of methyl isocyanate
    • Authors: Cassone G; Saija F, Sponer J, et al.
      Pages: 1565 - 1570
      Abstract: ABSTRACTAlthough complex organic molecules are observed in a wide variety of environments, chemical reaction networks heading to their formation are higly debated. It is a major endeavour to model the rates of reactions and incorporate them into chemical networks. The vast majority of the computational investigations in astrochemistry take into consideration oversimplified molecular models where chemical reactions are simulated under vacuum conditions (gas phase) and with crudely approximated entropic contributions to the free energy. We use density functional theory-based molecular dynamics techniques coupled with state-of-the-art metadynamics methods to investigate the role of ices embedding the reactants in shaping the free-energy landscape of selected reactions. Ices are chemically defined at the same level of theory of the reactants themselves. We consider as test case the transformation of methane and isocyanic acid into molecular hydrogen and methyl isocyanate, a species bearing similarities with peptide bonds. We examine the thermodynamically unfavoured case of very stable reactants to magnify modifications in the energy configuration induced by a solid amorphous water ice, either pure or mixed with CO. The presence of an active medium modifies significantly the free-energy surface, widening the path connecting reactants and products, and decreasing substantially the energy barriers. Ices not only act as gatherers of reactants, but also create thermodynamic conditions favouring chemical evolution.
      PubDate: Fri, 09 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab958
      Issue No: Vol. 504, No. 2 (2021)
  • Astrocladistics of the Jovian Trojan Swarms
    • Authors: Holt T; Horner J, Nesvorný D, et al.
      Pages: 1571 - 1608
      Abstract: ABSTRACTThe Jovian Trojans are two swarms of small objects that share Jupiter’s orbit, clustered around the leading and trailing Lagrange points, L4 and L5. In this work, we investigate the Jovian Trojan population using the technique of astrocladistics, an adaptation of the ‘tree of life’ approach used in biology. We combine colour data from WISE, SDSS, Gaia DR2, and MOVIS surveys with knowledge of the physical and orbital characteristics of the Trojans, to generate a classification tree composed of clans with distinctive characteristics. We identify 48 clans, indicating groups of objects that possibly share a common origin. Amongst these are several that contain members of the known collisional families, though our work identifies subtleties in that classification that bear future investigation. Our clans are often broken into subclans, and most can be grouped into 10 superclans, reflecting the hierarchical nature of the population. Outcomes from this project include the identification of several high priority objects for additional observations and as well as providing context for the objects to be visited by the forthcoming Lucy mission. Our results demonstrate the ability of astrocladistics to classify multiple large and heterogeneous composite survey data sets into groupings useful for studies of the origins and evolution of our Solar system.
      PubDate: Thu, 01 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab894
      Issue No: Vol. 504, No. 2 (2021)
  • Chandra large-scale mapping of the Galactic Centre: probing high-energy
           structures around the central molecular zone
    • Authors: Wang Q.
      Pages: 1609 - 1618
      Abstract: ABSTRACTRecent observations have revealed interstellar features that apparently connect energetic activity in the central region of our Galaxy to its halo. The nature of these features, however, remains largely uncertain. We present a Chandra mapping of the central 2° × 4° field of the Galaxy, revealing a complex of X-ray-emitting threads plus plume-like structures emerging from the Galactic Centre (GC). This mapping shows that the northern plume or fountain is offset from a well-known radio lobe (or the GCL), which however may represent a foreground H ii region, and that the southern plume is well wrapped by a corresponding radio lobe recently discovered by MeerKAT. In particular, we find that a distinct X-ray thread, G0.17−0.41, is embedded well within a non-thermal radio filament, which is locally inflated. This thread with a width of ∼1.6 arcsec (FWHM) is ∼2.6 arcmin or 6 pc long at the distance of the GC and has a spectrum that can be characterized by a power law or an optically-thin thermal plasma with temperature ≳ 3 keV. The X-ray-emitting material is likely confined within a strand of magnetic field with its strength ≳ 1 mG, not unusual in such radio filaments. These morphological and spectral properties of the radio/X-ray association suggest that magnetic field re-connection is the energy source. Such re-connection events are probably common when flux tubes of antiparallel magnetic fields collide and/or become twisted in and around the diffuse X-ray plumes, representing blowout superbubbles driven by young massive stellar clusters in the GC. The understanding of the process, theoretically predicted in analog to solar flares, can have strong implications for the study of interstellar hot plasma heating, cosmic ray acceleration and turbulence.
      PubDate: Tue, 27 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab801
      Issue No: Vol. 504, No. 2 (2021)
  • Measuring cosmological distances using cluster edges as a standard ruler
    • Authors: Wagoner E; Rozo E, Aung H, et al.
      Pages: 1619 - 1626
      Abstract: ABSTRACTThe line-of-sight velocity dispersion profile of galaxy clusters exhibits a ‘kink’ corresponding to the spatial extent of orbiting galaxies. Because the spatial extent of a cluster is correlated with the amplitude of the velocity dispersion profile, we can utilize this feature as a gravity-calibrated standard ruler. Specifically, the amplitude of the velocity dispersion data allows us to infer the physical cluster size. Consequently, observations of the angular scale of the ‘kink’ in the profile can be translated into a distance measurement to the cluster. Assuming the relation between cluster radius and cluster velocity dispersion can be calibrated from simulations, we forecast that with existing data from the Sloan Digital Sky Survey we will be able to measure the Hubble constant with 3.0 per cent precision. Implementing our method with data from the Dark Energy Spectroscopic Instrument (DESI) will result in a 1.3 per cent measurement of the Hubble constant. Adding cosmological supernova data improves the uncertainty of the DESI measurement to 0.7 per cent. While these error estimates are statistical only, they provide strong motivation for pursuing the necessary simulation program required to characterize and calibrate the systematic uncertainties impacting our proposed measurement. Whether or not our proposed measurement can in fact result in competitive H0 constraints will depend on what the eventual systematics floor for this method is.
      PubDate: Tue, 13 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1012
      Issue No: Vol. 504, No. 2 (2021)
  • X-ray spectroscopy of the starburst feedback in 30 Doradus
    • Authors: Cheng Y; Wang Q, Lim S.
      Pages: 1627 - 1643
      Abstract: ABSTRACTX-ray observations provide a potentially powerful tool to study starburst feedback. The analysis and interpretation of such observations remain challenging, however, due to various complications, including the non-isothermality of the diffuse hot plasma and the inhomogeneity of the foreground absorption. We here illustrate such complications and a way to mitigate their effects by presenting an X-ray spectroscopy of the 30 Doradus nebula in the Large Magellanic Clouds, based on a 100 ks Suzaku observation. We measure the thermal and chemical properties of the hot plasma and quantitatively confront them with the feedback expected from embedded massive stars. We find that our spatially resolved measurements can be well reproduced by a global modelling of the nebula with a lognormal temperature distribution of the plasma emission measure and a lognormal foreground absorption distribution. The metal abundances and total mass of the plasma are consistent with the chemically enriched mass ejection expected from the central OB association and a $\sim 55{{\ \rm per\ cent}}$ mass-loading from the ambient medium. The total thermal energy of the plasma is smaller than what is expected from a simple superbubble model, demonstrating that important channels of energy loss are not accounted for. Our analysis indeed shows tentative evidence for a diffuse non-thermal X-ray component, indicating that cosmic ray acceleration needs to be considered in such a young starburst region. Finally, we suggest that the lognormal modelling may be suitable for the X-ray spectral analysis of other giant H ii regions, especially when spatially resolved spectroscopy is not practical.
      PubDate: Thu, 15 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1040
      Issue No: Vol. 504, No. 2 (2021)
  • A detailed study of X-ray cavities in the intracluster environment of the
           cool core cluster Abell 3017
    • Authors: Pandge M; Sebastian B, Seth R, et al.
      Pages: 1644 - 1656
      Abstract: ABSTRACTWe present a detailed analysis of a cool-core galaxy cluster Abell 3017, at a redshift of z = 0.219, which has been identified to be merging with its companion cluster Abell 3016. This study has made use of X-ray (Chandra), ultraviolet (UV) [Galaxy Evolution Explorer(GALEX)], optical [European Southern Observatory (ESO)/very large telescope (VLT)], mid-infrared [(Wide-field Infrared Survey Explorer (WISE)], and radio upgraded Giant Metrewave radio telescope (uGMRT) observations of this cluster. Using various image processing techniques, such as unsharp masking, 2D fits using β models, contour binning and the use of surface brightness profiles, we show the existence of a pair of X-ray cavities, at a projected distance of ∼20 arcsec (70 kpc) and ∼16 arcsec (57 kpc), respectively, from the core of Abell 3017. We also detect an excess of X-ray emission located at ∼25 arcsec (88 kpc) south of the centre of Abell 3017, is likely due to the bulk motions in the intracluster medium either by gas sloshing or ram-pressure striping due to a merger. We find that the radio lobes are responsible for the observed X-ray cavities detected in this system. The lower values of mid-infrared WISE colour [W1–W2] and [W2–W3] imply that the central BCG of Abell 3017 is a star-forming galaxy. The current star formation rate of the central BCG, estimated from the H α and GALEX far-ultraviolet (FUV) luminosities, are equal to be ∼5.06 ± 0.78 and ∼9.20 ± 0.81 $\rm M_{\odot }$ yr−1, respectively. We detect, for the first time, a radio phoenix ∼150 kpc away from the radio core, with a spectral index of (α ≤ −1.8). We also report the detection of $\rm ~Pa\,\alpha$ emission in this cluster using ESO VLT SINFONI imaging data.
      PubDate: Fri, 05 Mar 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab384
      Issue No: Vol. 504, No. 2 (2021)
  • An enquiry on the origins of N-rich stars in the inner Galaxy based on
           APOGEE chemical compositions
    • Authors: Kisku S; Schiavon R, Horta D, et al.
      Pages: 1657 - 1667
      Abstract: ABSTRACTRecent evidence based on APOGEE data for stars within a few kpc of the Galactic Centre suggests that dissolved globular clusters (GCs) contribute significantly to the stellar mass budget of the inner halo. In this paper, we enquire into the origins of tracers of GC dissolution, N-rich stars, that are located in the inner 4 kpc of the Milky Way. From an analysis of the chemical compositions of these stars, we establish that about 30 per cent of the N-rich stars previously identified in the inner Galaxy may have an accreted origin. This result is confirmed by an analysis of the kinematic properties of our sample. The specific frequency of N-rich stars is quite large in the accreted population, exceeding that of its in situ counterparts by near an order of magnitude, in disagreement with predictions from numerical simulations. We hope that our numbers provide a useful test to models of GC formation and destruction.
      PubDate: Fri, 26 Feb 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab525
      Issue No: Vol. 504, No. 2 (2021)
  • IMF-induced intrinsic uncertainties on measuring galaxy distances based on
           the number of giant stars: the case of the ultradiffuse galaxy NGC
    • Authors: Zonoozi A; Haghi H, Kroupa P.
      Pages: 1668 - 1675
      Abstract: ABSTRACTThe surface brightness fluctuation (SBF) technique is one of the distance measurement methods that has been applied on the low surface brightness (LSB) galaxy NGC 1052-DF2 yielding a distance of about 20 Mpc implying it to be a dark matter deficient galaxy. We assume the number of giant stars above a given luminosity threshold to represent the SBF magnitude. The SBF magnitude depends on the distance, but this is degenerate with the star formation history (SFH). Using a stellar population synthesis model, we calculate the number of giant stars for stellar populations with different galaxy-wide stellar initial mass functions (gwIMFs), ages, metallicities, and SFHs. If the gwIMF is the invariant canonical IMF, the 1σ (3σ) uncertainty in colour allows a distance as low as 12 Mpc (8 Mpc). If instead the true underlying gwIMF is the integrated galaxy-wide IMF (IGIMF) then overestimating distances for low-mass galaxies would be a natural result, allowing NGC 1052-DF2 to have a distance of 11 Mpc within the 1σ colour uncertainty. Finally, we show that our main conclusion on the existence of a bias in the SBF distance estimation is not much affected by changing the luminosity lower limit for counting giant stars.
      PubDate: Thu, 18 Mar 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab789
      Issue No: Vol. 504, No. 2 (2021)
  • Erratum: Magnetohydrodynamical origin of eclipsing time variations in
           post-common-envelope binaries for solar mass secondaries
    • Authors: Navarrete F; Schleicher D, Käpylä P, et al.
      Pages: 1676 - 1676
      Abstract: errata, addendadynamoMHDmethods: numericalbinaries: eclipsingstars: rotation
      PubDate: Tue, 27 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab836
      Issue No: Vol. 504, No. 2 (2021)
  • The structural evolution of isolated galaxies at low redshift in the
           IllustrisTNG simulation
    • Authors: Walters D; Woo J, Ellison S, et al.
      Pages: 1677 - 1693
      Abstract: ABSTRACTWe study the structural evolution of isolated star-forming (SF) galaxies in the IllustrisTNG100-1 hydrodynamical simulation, with a focus on investigating the growth of the central core density within 2 kpc (Σ*,2 kpc) in relation to total stellar mass (M*) at z < 0.5. First, we show that several observational trends in the Σ*,2 kpc–M* plane are qualitatively reproduced in IllustrisTNG, including the distributions of active galactic nuclei (AGN), SF galaxies, quiescent galaxies, and radial profiles of stellar age, specific star formation rate (sSFR), and metallicity. We find that galaxies with dense cores evolve parallel to the Σ*,2 kpc–M* relation, while galaxies with diffuse cores evolve along shallower trajectories. We investigate possible drivers of rapid growth in Σ*,2 kpc compared to M*. Both the current sSFR gradient and the black hole (BH) accretion rate are indicators of past core growth, but are not predictors of future core growth. Major mergers (although rare in our sample; ∼10 per cent) cause steeper core growth, except for high-mass ($M_{\rm *}\gtrsim 10^{10} \, {\rm M}_{\odot }$) mergers, which are mostly dry. Disc instabilities, as measured by the fraction of mass with Toomre Q < 2, are not predictive of rapid core growth. Instead, rapid core growth results in more stable discs. The cumulative BH feedback history sets the maximum rate of core growth, preventing rapid growth in high-mass galaxies ($\gtrsim 10^{9.5} \, {\rm M}_{\odot }$). For massive galaxies, the total specific angular momentum of accreting gas is the most important predictor of future core growth. Our results suggest that the angular momentum of accreting gas controls the slope, width, and zero-point evolution of the Σ*,2 kpc–M* relation.
      PubDate: Wed, 24 Mar 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab840
      Issue No: Vol. 504, No. 2 (2021)
  • Statistical exploration of halo anisotropic clustering and intrinsic
           alignments with the mass-Peak Patch algorithm
    • Authors: Regaldo-Saint Blancard B; Codis S, Bond J, et al.
      Pages: 1694 - 1713
      Abstract: ABSTRACTThe anisotropy or triaxiality of massive dark matter haloes largely defines the structure of the cosmic web, in particular the filaments that join the haloes together. Here, we investigate such oriented correlations in mass-Peak Patch halo catalogues by using the initial strain tensor of spherical proto-halo regions to orient the haloes. To go beyond the spherically averaged two-point correlation function of haloes, we use oriented stacks to compute oriented two-point correlations: we explicitly break isotropy by imposing a local frame set by the strain tensor of the reference halo before stacking neighbouring haloes. Beyond the exclusion zone of the reference halo, clustering is found to be strongly enhanced along the major direction of the strain tensor as expected. This anisotropic clustering of haloes along filaments is further quantified by using a spherical harmonics decomposition. Furthermore, we compute the evolution of cluster-scale halo principal directions relative to those of their neighbours and show that there are strong correlations extending up to very large scales. In order to provide calculations more suitable to observational confrontations, we also utilize 2D projected versions of some equivalent correlation functions. Finally, we show that the multipole structure of the mass-peak patch halo’s anisotropic clustering can be qualitatively captured in an analytic treatment based on peak theory. Though highly informative, giving the same qualitative features as the oriented correlations found from the simulation catalogue, analytic evaluation involves extensive use of Monte Carlo methods, which is also what the simulated catalogue uses, taking into account as they do the adaptive nature of the mass-peak patch mass hierarchy and all non-local complexities associated with the exclusion of smaller haloes overlapping with larger ones: there is no substitute for the mass-Peak Patch simulation-based determination of oriented and anisotropic correlations.
      PubDate: Fri, 23 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab927
      Issue No: Vol. 504, No. 2 (2021)
  • Solution intervals considered harmful: on the optimality of radio
           interferometric gain solutions
    • Authors: Sob U; Bester H, Smirnov O, et al.
      Pages: 1714 - 1732
      Abstract: ABSTRACTSolution intervals are often used to improve the signal-to-noise ratio during radio interferometric gain calibration. This work investigates how factors such as the noise level, intrinsic gain variability, degree of model incompleteness, and the presence of radio frequency interference impact the selection of solution intervals for calibration. We perform different interferometric simulations to demonstrate how these factors, in combination with the choice of solution intervals, affect calibration and imaging outputs and discuss practical guidelines for choosing optimal solution intervals. Furthermore, we present an algorithm capable of automatically selecting suitable solution intervals during calibration. By applying the algorithm to both simulated and real data, we show that it can successfully choose solution intervals that strike a good balance between capturing intrinsic gain variability and not fitting noise as long as the data are not too inhomogeneously flagged. Furthermore, we elaborate on several practical aspects that emphasize the need to develop regularized calibration algorithms that do not require solution intervals.
      PubDate: Mon, 05 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab928
      Issue No: Vol. 504, No. 2 (2021)
  • Thermal formaldehyde emission in NGC 7538 IRS 1
    • Authors: Shuvo O; Araya E, Tan W, et al.
      Pages: 1733 - 1748
      Abstract: ABSTRACTSpectral lines from formaldehyde (H2CO) molecules at cm wavelengths are typically detected in absorption and trace a broad range of environments, from diffuse gas to giant molecular clouds. In contrast, thermal emission of formaldehyde lines at cm wavelengths is rare. In previous observations with the 100 m Robert C. Byrd Green Bank Telescope (GBT), we detected 2 cm formaldehyde emission towards NGC 7538 IRS1 – a high-mass protostellar object in a prominent star-forming region of our Galaxy. We present further GBT observations of the 2 and 1 cm H2CO lines to investigate the nature of the 2 cm H2CO emission. We conducted observations to constrain the angular size of the 2 cm emission region based on a East–West and North–South cross-scan map. Gaussian fits of the spatial distribution in the East–West direction show a deconvolved size (at half maximum) of the 2 cm emission of 50 arcsec ± 8 arcsec. The 1 cm H2CO observations revealed emission superimposed on a weak absorption feature. A non-LTE radiative transfer analysis shows that the H2CO emission is consistent with quasi-thermal radiation from dense gas (${\sim}10^5$–$10^6$ cm−3). We also report detection of four transitions of CH3OH (12.2, 26.8, 28.3, 28.9 GHz), the (8,8) transition of NH3 (26.5 GHz), and a cross-scan map of the 13 GHz SO line that shows extended emission (>50 arcsec).
      PubDate: Mon, 05 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab933
      Issue No: Vol. 504, No. 2 (2021)
  • MERGHERS pilot: MeerKAT discovery of diffuse emission in nine massive
           Sunyaev–Zel’dovich-selected galaxy clusters from ACT
    • Authors: Knowles K; Pillay D, Amodeo S, et al.
      Pages: 1749 - 1758
      Abstract: ABSTRACTThe MeerKAT Exploration of Relics, Giant Halos, and Extragalactic Radio Sources (MERGHERS) survey is a planned project to study a large statistical sample of galaxy clusters with the MeerKAT observatory. Here we present the results of a 16-h pilot project, observed in response to the 2019 MeerKAT Shared Risk proposal call, to test the feasibility of using MeerKAT for a large cluster study using short (0.2–2.1 h) integration times. The pilot focuses on 1.28-GHz observations of 13 massive, low-to-intermediate redshift (0.22 < z < 0.65) clusters from the Sunyaev–Zel’dovich-selected Atacama Cosmology Telescope (ACT) DR5 catalogue that show multiwavelength indications of dynamical disturbance. With a 70 per cent detection rate (9/13 clusters), this pilot study validates our proposed MERGHERS observing strategy and provides twelve detections of diffuse emission, eleven of them new, indicating the strength of MeerKAT for such types of studies. The detections (signal-to-noise ratio ≳ 6) are summarized as follows: two systems host both relic(s) and a giant radio halo, five systems host radio haloes, and two have candidate radio haloes. Power values, k-corrected to 1.4 GHz, assuming a fiducial spectral index of α = −1.3 ± 0.4, are consistent with known radio halo and relic scaling relations.
      PubDate: Mon, 05 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab939
      Issue No: Vol. 504, No. 2 (2021)
  • An energy-conserving dynamical model of GRB afterglows from magnetized
           forward and reverse shocks
    • Authors: Chen Q; Liu X.
      Pages: 1759 - 1771
      Abstract: ABSTRACTIn the dynamical models of gamma-ray burst (GRB) afterglows, the uniform assumption of the shocked region is known as provoking total energy conservation problem. In this work, we consider shocks originating from magnetized ejecta and extend the energy-conserving hydrodynamical model of Yan, Wei & Fan to the MHD limit by applying the magnetized jump conditions from Zhang & Kobayashi. Compared with the non-conservative models, our Lorentz factor of the whole shocked region is larger by a factor ${\lesssim}\sqrt{2}$. The total pressure of the forward shocked region is higher than the reversed shocked region, in the relativistic regime with a factor of about 3 in our interstellar medium (ISM) cases while ejecta magnetization degree σ < 1, and a factor of about 2.4 in the wind cases. For σ ≤ 1, the non-conservative model loses 32–42 per cent of its total energy for ISM cases, and for wind cases 25–38 per cent, which happens specifically in the forward shocked region, making the shock synchrotron emission from the forward shock less luminous than expected. Once the energy conservation problem is fixed, the late-time light curves from the forward shock become nearly independent of the ejecta magnetization. The reverse shocked region does not suffer from the energy conservation problem since the changes of the Lorentz factor are recompensed by the changes of the shocked particle number density. The early light curves from the reverse shock are sensitive to the magnetization of the ejecta, thus are an important probe of the magnetization degree.
      PubDate: Mon, 05 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab946
      Issue No: Vol. 504, No. 2 (2021)
  • Correlation between optical and γ-ray flux variations in BL Lacs
    • Authors: Rajput B; Shah Z, Stalin C, et al.
      Pages: 1772 - 1786
      Abstract: ABSTRACTWe report here results of the analysis of correlated flux variations between the optical and GeV γ-ray bands in three bright BL Lac objects, namely AO 0235+164, OJ 287, and PKS 2155−304. This was based on the analysis of about 10 yr of data from the Fermi Gamma-ray Space Telescope covering the period between 2008 August 8 and 2018 August 8 along with optical data covering the same period. For all the sources, during the flares analysed in this work, the optical and γ-ray flux variations are found to be closely correlated. From broad-band spectral energy distribution modelling of different epochs in these sources using the one-zone leptonic emission model, we found that the optical–ultraviolet emission is dominated by synchrotron emission from the jet. The γ-ray emission in the low synchrotron peaked sources AO 0235+164 and OJ 287 is found to be well fitted with external Compton (EC) component, while the γ-ray emission in the high synchrotron peaked source PKS 2155−304 is well fitted with synchrotron self-Compton component. Further, we note that the γ-ray emission during the high-flux state of AO 0235+164 (epochs A and B) requires seed photons from both the dusty torus and broad-line region, while the γ-ray emission in OJ 287 and during epochs C and D of AO 0235+164 can be modelled by EC scattering of infrared photons from the torus.
      PubDate: Sat, 10 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab970
      Issue No: Vol. 504, No. 2 (2021)
  • Artificial intelligence and quasar absorption system modelling;
           application to fundamental constants at high redshift
    • Authors: Lee C; Webb J, Carswell R, et al.
      Pages: 1787 - 1800
      Abstract: ABSTRACTWe have developed a new fully automated Artificial Intelligence (AI)-based method for deriving optimal models of complex absorption systems. The AI structure is built around VPFIT, a well-developed and extensively tested nonlinear least-squares code. The new method forms a sophisticated parallelized system, eliminating human decision-making and hence bias. Here, we describe the workings of such a system and apply it to synthetic spectra, in doing so establishing recommended methodologies for future analyses of Very Large Telescope (VLT) and Extremely Large Telescope (ELT) data. One important result is that modelling line broadening for high-redshift absorption components should include both thermal and turbulent components. Failing to do so means it is easy to derive the wrong model and hence incorrect parameter estimates. One topical application of our method concerns searches for spatial or temporal variations in fundamental constants. This subject is one of the key science drivers for the European Southern Observatory’s ESPRESSO spectrograph on the VLT and for the HIRES spectrograph on the ELT. The quality of new data demands completely objective and reproducible methods. The Monte Carlo aspects of the new method described here reveal that model non-uniqueness can be significant, indicating that it is unrealistic to expect to derive an unambiguous estimate of the fine structure constant α from one or a very small number of measurements. No matter how optimal the modelling method, it is a fundamental requirement to use a large sample of measurements to meaningfully constrain temporal or spatial α variation.
      PubDate: Fri, 09 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab977
      Issue No: Vol. 504, No. 2 (2021)
  • A lack of constraints on the cold opaque H i mass: H i spectra in M31
           and M33 prefer multicomponent models over a single cold opaque component
    • Authors: Koch E; Rosolowsky E, Leroy A, et al.
      Pages: 1801 - 1824
      Abstract: ABSTRACTPrevious work has argued that atomic gas mass estimates of galaxies from 21-cm H i emission are systematically low due to a cold opaque atomic gas component. If true, this opaque component necessitates a $\sim 35{{\ \rm per\ cent}}$ correction factor relative to the mass from assuming optically thin H i emission. These mass corrections are based on fitting H i spectra with a single opaque component model that produces a distinct ‘top-hat’ shaped line profile. Here, we investigate this issue using deep, high spectral resolution H i VLA observations of M31 and M33 to test if these top-hat profiles are instead superpositions of multiple H i components along the line of sight. We fit both models and find that ${\gt}80{{\ \rm per\ cent}}$ of the spectra strongly prefer a multicomponent Gaussian model while ${\lt}2{{\ \rm per\ cent}}$ prefer the single opacity-corrected component model. This strong preference for multiple components argues against previous findings of lines of sight dominated by only cold H i. Our findings are enabled by the improved spectral resolution (0.42 ${\rm km\, s^{-1}}$), whereas coarser spectral resolution blends multiple components together. We also show that the inferred opaque atomic ISM mass strongly depends on the goodness-of-fit definition and is highly uncertain when the inferred spin temperature has a large uncertainty. Finally, we find that the relation of the H i surface density with the dust surface density and extinction has significantly more scatter when the inferred H i opacity correction is applied. These variations are difficult to explain without additionally requiring large variations in the dust properties. Based on these findings, we suggest that the opaque H i mass is best constrained by H i absorption studies.
      PubDate: Fri, 09 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab981
      Issue No: Vol. 504, No. 2 (2021)
  • Noise reduction for weak lensing mass mapping: an application of
           generative adversarial networks to Subaru Hyper Suprime-Cam first-year
    • Authors: Shirasaki M; Moriwaki K, Oogi T, et al.
      Pages: 1825 - 1839
      Abstract: ABSTRACTWe propose a deep-learning approach based on generative adversarial networks (GANs) to reduce noise in weak lensing mass maps under realistic conditions. We apply image-to-image translation using conditional GANs to the mass map obtained from the first-year data of Subaru Hyper Suprime-Cam (HSC) Survey. We train the conditional GANs by using 25 000 mock HSC catalogues that directly incorporate a variety of observational effects. We study the non-Gaussian information in denoised maps using one-point probability distribution functions (PDFs) and also perform matching analysis for positive peaks and massive clusters. An ensemble learning technique with our GANs is successfully applied to reproduce the PDFs of the lensing convergence. About $60{{\ \rm per\ cent}}$ of the peaks in the denoised maps with height greater than 5σ have counterparts of massive clusters within a separation of 6 arcmin. We show that PDFs in the denoised maps are not compromised by details of multiplicative biases and photometric redshift distributions, nor by shape measurement errors, and that the PDFs show stronger cosmological dependence compared to the noisy counterpart. We apply our denoising method to a part of the first-year HSC data to show that the observed mass distribution is statistically consistent with the prediction from the standard ΛCDM model.
      PubDate: Fri, 09 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab982
      Issue No: Vol. 504, No. 2 (2021)
  • Explaining the extended GeV gamma-ray emission adjacent to
           HESS J1825-137
    • Authors: Collins T; Rowell G, Mitchell A, et al.
      Pages: 1840 - 1853
      Abstract: ABSTRACTHESS J1825-137 is one of the most powerful and luminous TeV gamma-ray pulsar wind nebulae (PWN). To the south of HESS J1825-137, Fermi-LAT observation revealed a new region of GeV gamma-ray emission with three apparent peaks (termed here, GeV-ABC). This study presents interstellar medium (ISM) data and spectral energy distribution (SED) modelling towards the GeV emission to understand the underlying particle acceleration. We considered several particle accelerator scenarios – the PWN associated with HESS J1825-137, the progenitor SNR also associated with HESS J1825-137, plus the gamma-ray binary system LS 5039. It was found that the progenitor SNR of HESS J1825-137 has insufficient energetics to account for all GeV emission. GeV-ABC may be a reflection of an earlier epoch in the history of the PWN associated with HESS 1825-137, assuming fast diffusion perhaps including advection. LS 5039 cannot meet the required energetics to be the source of particle acceleration. A combination of HESS J1825-137 and LS 5039 could be plausible sources.
      PubDate: Sat, 10 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab983
      Issue No: Vol. 504, No. 2 (2021)
  • Building the Galilean moons system via pebble accretion and migration: a
           primordial resonant chain
    • Authors: Madeira G; Izidoro A, Giuliatti Winter S.
      Pages: 1854 - 1872
      Abstract: ABSTRACTThe origins of the Galilean satellites – namely Io, Europa, Ganymede, and Callisto – is not fully understood yet. Here we use N-body numerical simulations to study the formation of Galilean satellites in a gaseous circumplanetary disc around Jupiter. Our model includes the effects of pebble accretion, gas-driven migration, and gas tidal damping and drag. Satellitesimals in our simulations first grow via pebble accretion and start to migrate inwards. When they reach the trap at the disc inner edge, scattering events and collisions take place promoting additional growth. Growing satellites eventually reach a multiresonant configuration anchored at the disc inner edge. Our results show that an integrated pebble flux of ≥2 × 10−3 MJ results in the formation of satellites with masses typically larger than those of the Galilean satellites. Our best match to the masses of the Galilean satellites is produced in simulations where the integrated pebble flux is ∼10−3 MJ. These simulations typically produce between three and five satellites. In our best analogues, adjacent satellite pairs are all locked in 2:1 mean motion resonances. However, they have also moderately eccentric orbits (∼0.1), unlike the current real satellites. We propose that the Galilean satellites system is a primordial resonant chain, similar to exoplanet systems as TRAPPIST-1, Kepler-223, and TOI-178. Callisto was probably in resonance with Ganymede in the past but left this configuration – without breaking the Laplacian resonance – via divergent migration due to tidal planet–satellite interactions. These same effects further damped the orbital eccentricities of these satellites down to their current values (∼0.001). Our results support the hypothesis that Io and Europa were born with water-ice rich compositions and lost all/most of their water afterwards. Firmer constraints on the primordial compositions of the Galilean satellites are crucial to distinguish formation models.
      PubDate: Mon, 12 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab986
      Issue No: Vol. 504, No. 2 (2021)
  • Searching for new solar twins: The Inti survey for the Northern Sky
    • Authors: Yana Galarza J; López-Valdivia R, Lorenzo-Oliveira D, et al.
      Pages: 1873 - 1887
      Abstract: ABSTRACTSolar twins are key in different areas of astrophysics, however only just over a hundred were identified and well-studied in the last two decades. In this work, we take advantage of the very precise Gaia (DR2/EDR3), Tycho, and 2MASS photometric systems to create the ${{Inti}}$ survey of new solar twins in the Northern Hemisphere. The spectra of our targets were initially obtained with spectrographs of moderate resolution (ARCES and Goodman spectrographs with R  = 31 500 and 11 930, respectively) to find the best solar twin candidates and then observed at McDonald Observatory with higher resolving power (TS23, R  = 60 000) and signal-to-noise ratio (SNR ∼ 300–500). The stellar parameters were estimated through the differential spectroscopic equilibrium relative to the Sun, which allow us to achieve a high internal precision (σ(Teff)  = 15 K, σ(log g)  = 0.03 dex, σ($\rm {[Fe/H]}$)  = 0.01 dex, and σ(vt)  = 0.03 km s−1). We propose a new class of stars with evolution similar to the Sun: solar proxy, which is useful to perform studies related to the evolution of the Sun, such as its rotational and magnetic evolution. Its definition is based on metallicity (−0.15 dex ≤ $\rm {[Fe/H]}$ ≤  + 0.15 dex) and mass (0.95 M⊙ ≤ M ≤ 1.05 M⊙) constraints, thus assuring that the star follows a similar evolutionary path as the Sun along the main sequence. Based on this new definition, we report 70 newly identified solar proxies, 46 solar analogues, and 13 solar-type stars. In addition, we identified nine close solar twins whose stellar parameters are the most similar to those of the Sun.
      PubDate: Sat, 10 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab987
      Issue No: Vol. 504, No. 2 (2021)
  • Interacting galaxies in the IllustrisTNG simulations – III. (The rarity
           of) quenching in post-merger galaxies
    • Authors: Quai S; Hani M, Ellison S, et al.
      Pages: 1888 - 1901
      Abstract: ABSTRACTGalaxy mergers are traditionally one of the favoured mechanisms for the transformation of spiral galaxies to spheroids and for quenching star formation. To test this paradigm in the context of modern cosmological simulations, we use the IllustrisTNG simulation to investigate the impact of individual merger events on quenching star formation [i.e. star formation rate (SFR) at least 3σ below the star-forming main sequence] within 500 Myr after the coalescence phase. The rate of quenching amongst recently merged galaxies is compared with a control sample that is matched in redshift, stellar mass, SFR, black hole mass, and environment. We find quenching to be uncommon among the descendants of post-merger galaxies, with only ${\sim} 5{{\ \rm per\ cent}}$ of galaxies quenching within 500 Myr after the merger. Despite this low absolute rate, we find that quenching occurs in post-mergers at twice the rate of the control galaxies. The fraction of quenched post-merger descendants 1.5 Gyr after the merger become statistically indistinguishable from that of non-post-mergers, suggesting that mergers could speed up the quenching process in those post-mergers whose progenitors had physical conditions able to sustain effective active galactic nuclei (AGN) kinetic feedback, thus capable of removing gas from galaxies. Our results indicate that although quenching does not commonly occur promptly after coalescence, mergers none the less do promote the cessation of star formation in some post-mergers. We find that, in IllustrisTNG, it is the implementation of the AGN kinetic feedback that is responsible for quenching post-mergers, as well as non-post-merger controls. As a result of the released kinetic energy, galaxies experience gas loss and eventually they will quench. Galaxies with an initially low gas fraction show a preferable pre-disposition towards quenching. The primary distinguishing factor between quenched and star-forming galaxies is gas fraction, with a sharp boundary at fgas ∼ 0.1 in TNG.
      PubDate: Mon, 12 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab988
      Issue No: Vol. 504, No. 2 (2021)
  • Ly α as a tracer of cosmic reionization in the SPHINX
           radiation-hydrodynamics cosmological simulation
    • Authors: Garel T; Blaizot J, Rosdahl J, et al.
      Pages: 1902 - 1926
      Abstract: ABSTRACTThe Ly α emission line is one of the most promising probes of cosmic reionization but isolating the signature of a change in the ionization state of the intergalactic medium (IGM) is challenging because of intrinsic evolution and internal radiation transfer effects. We present the first study of the evolution of Ly α emitters (LAE) during the epoch of reionization based on a full radiation-hydrodynamics cosmological simulation that is able to capture both the large-scale process of reionization and the small-scale properties of galaxies. We predict the Ly α emission of galaxies in the 103 cMpc3sphinx simulation at 6 ≤ z ≤ 9 by computing the full Ly α radiation transfer from interstellar medium (ISM) to IGM scales. sphinx is able to reproduce many observational constraints such as the UV/Ly α luminosity functions and stellar mass functions at z ≳ 6 for the dynamical range probed by our simulation (M1500 ≳ −18, LLy α ≲ 1042 erg s−1, M⋆ ≲ 109 M⊙). As intrinsic Ly α emission and internal Ly α escape fractions barely evolve from z = 6–9, the observed suppression of Ly α luminosities with increasing redshift is fully attributed to IGM absorption. For most observable galaxies (M1500 ≲ −16), the Ly α line profiles are slightly shifted to the red due to internal radiative transfer effects that mitigates the effect of IGM absorption. Overall, the enhanced Ly α suppression during reionization traces the IGM neutral fraction $x_{{\rm H\, {i}}}$ well, but the predicted amplitude of this reduction is a strong function of the Ly α peak shift, which is set at ISM/circumgalactic medium scales. We find that a large number of LAEs could be detectable in very deep surveys during reionization when $x_{{\rm H\, {i}}}$ is still $\approx 50{{\ \rm per\ cent}}$.
      PubDate: Wed, 14 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab990
      Issue No: Vol. 504, No. 2 (2021)
  • Contribution of statistical site learning to improve optical turbulence
    • Authors: Giordano C; Rafalimanana A, Ziad A, et al.
      Pages: 1927 - 1938
      Abstract: ABSTRACTThe forecast for atmospheric and turbulence conditions above astronomical observatories is of interest to the astronomical community because it allows observations to be planned with maximum efficiency, a process called flexible scheduling. It can also be used to simulate long-term site testing to provide local information useful for the conception of focal and post-focal instrumentation. We have presented our forecasting tool in previous publications, but in this paper we focus on the importance of using local measurements to improve the predictive turbulence model and to better consider the local specificities of a given site, a process we call site learning. For this study, we use a local data base provided by the Calern Atmospheric Turbulence Station, which has been operational since 2015 at Calern Observatory. In addition, we use a set of several months of predictions to feed the turbulence model, taking into account daytime and nighttime conditions. This upgrade improves the quality of our forecasting by reducing the absolute bias between measurements and predictions from 25 to 50 per cent for each layer of the $C_n^2$, by 25 per cent for the seeing, and by 70 per cent for the isoplanatic angle.
      PubDate: Wed, 28 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/staa3709
      Issue No: Vol. 504, No. 2 (2021)
  • Temporal evolution of prompt GRB polarization
    • Authors: Gill R; Granot J.
      Pages: 1939 - 1958
      Abstract: ABSTRACTThe dominant radiation mechanism that produces the prompt emission in gamma-ray bursts (GRBs) remains a major open question. Spectral information alone has proven insufficient in elucidating its nature. Time-resolved linear polarization has the potential to distinguish between popular emission mechanisms, e.g. synchrotron radiation from electrons with a power-law energy distribution or inverse Compton scattering of soft seed thermal photons, which can yield the typical GRB spectrum but produce different levels of polarization. Furthermore, it can be used to learn about the outflow’s composition (i.e. whether it is kinetic-energy-dominated or Poynting-flux-dominated) and angular structure. For synchrotron emission, it is a powerful probe of the magnetic field geometry. Here, we consider synchrotron emission from a thin ultrarelativistic outflow, with bulk Lorentz factor Γ(R) = Γ0(R/R0)−m/2 ≫ 1, that radiates a Band-function spectrum in a single (multiple) pulse(s) over a range of radii, R0 ≤ R ≤ R0 + ΔR. Pulse profiles and polarization evolution at a given energy are presented for a coasting (m = 0) and accelerating (m = −2/3) thin spherical shell and for different viewing angles for a top-hat jet with sharp as well as smooth edges in emissivity. Four different magnetic field configurations are considered, such as a locally ordered field coherent over angular scales θB ≳ 1/Γ, a tangled field (B⊥) in the plane transverse to the radial direction, an ordered field (B∥) aligned in the radial direction, and a globally ordered toroidal field (Btor). All field configurations produce distinct polarization evolution with single (for B⊥ and B∥) and double (for Btor) 90○ changes in the polarization position angle.
      PubDate: Mon, 12 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1013
      Issue No: Vol. 504, No. 2 (2021)
  • Probing possible effects of circumgalactic media on the metal content of
           galaxies through the mass–metallicity relationship
    • Authors: Zhai S; Shi Y, Chen J, et al.
      Pages: 1959 - 1968
      Abstract: ABSTRACTThe circumgalactic medium (CGM) connects the gas between the interstellar medium and the intergalactic medium, which plays an important role in galaxy evolution. We use the stellar mass–metallicity relationship to investigate whether sharing the CGM will affect the distribution of metals in galaxy pairs. The optical emission lines from the Sloan Digital Sky Survey Data Release are used to measure the gas-phase metallicity. We find that there is no significant difference in the distribution of the metallicity difference between two members in star forming–star forming pairs ($\rm \Delta log(O/H)_{diff}$), metallicity offset from the best-fitting stellar mass–metallicity relationship of galaxies in pairs ($\rm \Delta log(O/H)_{MS}$), as compared to ‘fake’ pairs. By looking at and as a function of the star formation rate (SFR), specific SFR, and stellar mass ratio, no difference is seen between galaxies in pairs and control galaxies. From our results, the share of the CGM may not play an important role in shaping the evolution of metal contents of galaxies.
      PubDate: Wed, 14 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1017
      Issue No: Vol. 504, No. 2 (2021)
  • Magnetic field and activity phenomena of the K2 dwarf V471 Tau
    • Authors: Zaire B; Donati J, Klein B.
      Pages: 1969 - 1988
      Abstract: ABSTRACTWe analyse spectropolarimetric data of the pre-cataclysmic variable binary system V471 Tau obtained with ESPaDOnS at the Canada–France–Hawaii Telescope in two observational campaigns (in 2004 November/December and 2005 December). Using Zeeman–Doppler imaging, we reconstruct the distribution of brightness map and large-scale magnetic field of the K2 dwarf at both epochs, as well as the amount of differential rotation by which surface maps are sheared. We detect significant fluctuations in the surface shear between the two campaigns. It goes from about twice the solar differential rotation rate to less than the solar value in a 1-yr interval. We conclude that the differential rotation fluctuations obtained for the K2 dwarf resemble those detected on the single-star analogue AB Dor, although even larger amplitudes of variation are seen in the K2 dwarf of V471 Tau. Finally, we show that the differential rotation results obtained in this work do not favour an Applegate mechanism operating in the V471 Tau system, at least in its standard form, but leave room for explaining the observed orbital period fluctuations with exotic forms of similar phenomena based on dynamo processes operating within the convective zone of the K2 star.
      PubDate: Wed, 14 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1019
      Issue No: Vol. 504, No. 2 (2021)
  • On the relationship between gas content, star formation, and global H i
           asymmetry of galaxies on the star-forming main-sequence
    • Authors: Watts A; Catinella B, Cortese L, et al.
      Pages: 1989 - 1998
      Abstract: ABSTRACTObservations have revealed that disturbances in the cold neutral atomic hydrogen (H i) in galaxies are ubiquitous, but the reasons for these disturbances remain unclear. While some studies suggest that asymmetries in integrated H i spectra (global H i asymmetry) are higher in H i-rich systems, others claim that they are preferentially found in H i-poor galaxies. In this work, we utilize the Arecibo Legacy Fast ALFA (ALFALFA) and extended GALEX Arecibo SDSS Survey (xGASS) surveys, plus a sample of post-merger galaxies, to clarify the link between global H i asymmetry and the gas properties of galaxies. Focusing on star-forming galaxies in ALFALFA, we find that elevated global H i asymmetry is not associated with a change in the H i content of a galaxy, and that only the galaxies with the highest global H i asymmetry show a small increase in specific star formation rate (sSFR). However, we show that the lack of a trend with H i content is because ALFALFA misses the ‘gas-poor’ tail of the star-forming main-sequence. Using xGASS to obtain a sample of star-forming galaxies that is representative in both sSFR and H i content, we find that global H i asymmetric galaxies are typically more gas-poor than symmetric ones at fixed stellar mass, with no change in sSFR. Our results highlight the complexity of the connection between galaxy properties and global H i asymmetry. This is further confirmed by the fact that even post-merger galaxies show both symmetric and asymmetric H i spectra, demonstrating that merger activity does not always lead to an asymmetric global H i spectrum.
      PubDate: Thu, 15 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1025
      Issue No: Vol. 504, No. 2 (2021)
  • The stellar mass function and evolution of the density profile of galaxy
           clusters from the Hydrangea simulations at 0 < z < 1.5
    • Authors: Ahad S; Bahé Y, Hoekstra H, et al.
      Pages: 1999 - 2013
      Abstract: ABSTRACTGalaxy clusters are excellent probes to study the effect of environment on galaxy formation and evolution. Along with high-quality observational data, accurate cosmological simulations are required to improve our understanding of galaxy evolution in these systems. In this work, we compare state-of-the-art observational data of massive galaxy clusters ($\gt 10^{14}\, \textrm {M}_{\odot }$) at different redshifts (0 < z < 1.5) with predictions from the Hydrangea suite of cosmological hydrodynamic simulations of 24 massive galaxy clusters ($\gt 10^{14}\, \textrm {M}_{\odot }$ at z = 0). We compare three fundamental observables of galaxy clusters: the total stellar mass-to-halo mass ratio, the stellar mass function, and the radial mass density profile of the cluster galaxies. In the first two of these, the simulations agree well with the observations, albeit with a slightly too high abundance of $M_\star \lesssim 10^{10} \, \mathrm{M}_\odot$ galaxies at z ≳ 1. The Navarro–Frenk–White concentrations of cluster galaxies increase with redshift, in contrast to the decreasing dark matter (DM) halo concentrations. This previously observed behaviour is therefore due to a qualitatively different assembly of the smooth DM halo compared to the satellite population. Quantitatively, we, however, find a discrepancy in that the simulations predict higher stellar concentrations than observed at lower redshifts (z < 0.3), by a factor of ≈2. This may be due to selection bias in the simulations, or stem from shortcomings in the build-up and stripping of their inner satellite halo.
      PubDate: Fri, 16 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1036
      Issue No: Vol. 504, No. 2 (2021)
  • Confined massive circumstellar shell in type IIL SN 2008fq
    • Authors: Chugai N.
      Pages: 2014 - 2018
      Abstract: ABSTRACTI explore a phenomenon of the circumstellar H α and H β absorption lines in the spectrum of the luminous type IIL SN 2008fq taken on day 6.8 after the discovery. The absorption is identified with the radiatively accelerated pre-shock wind up to ∼800 km s−1. The required initial luminosity is attributed to earlier circumstellar interaction with the confined dense shell of ∼0.08 M⊙. Modelling of a similar luminous type IIL SN 1998S based on the same approach results in a comparable shell mass of ∼0.1 M⊙. The larger mass of more than 1 dex for the confined dense shells of both SNe IIL compared to that of type IIP supernovae is attributed to the larger progenitor mass of type IIL supernovae.
      PubDate: Wed, 28 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1055
      Issue No: Vol. 504, No. 2 (2021)
  • Characterization of V-type asteroids orbiting in the middle and outer main
    • Authors: Migliorini A; De Sanctis M, Michtchenko T, et al.
      Pages: 2019 - 2032
      Abstract: ABSTRACTWe present new spectral observations using ground-based telescopes of 23 putative V-type asteroids, selected according to colour surveys in the visible from the Moving Objects Catalogue of the Sloan Digital Sky Survey and near-infrared from the Moving Objects VISTA catalogue. 10 asteroids are orbiting in the middle main belt, while five in the outer part of the main asteroid belt. For the observed asteroids, we assign a taxonomical classification and confirm the basaltic nature for 16 of them. The high-quality spectra in the UV range, obtained with the X-Shooter spectrograph at ESO, allowed the identification of the Fe2+ forbidden transition of pyroxene for 10 asteroids. This band is centred at 506.5 nm, and it is diagnostic of the Ca-content in the pyroxene form. We determined a low Fe-content composition for asteroids (2452) Lyot, (5758) Brunini, (7675) Gorizia, (9197) Endo, (22308) 1990 UO4, (36118) 1999 RE135, (66905) 1999 VC160, and (189597) 2000 WG119, and a composition more rich in Fe for asteroids (75661) 2000 AB79 and (93620) 2000 UQ70. We also present a dynamical investigation of V-type asteroids in the middle and outer main belt. The principal finding of these simulations is that the middle and outer V-types are more likely to be associated with some families, which were considered as possibly originated from the break up of a partially or totally differentiated parent body by diverse studies. This reinforces the hypothesis that the identified V-type in the region were not originated from (4) Vesta and that the number of differentiated objects in the middle and outer main belt must have been much larger than previously assumed.
      PubDate: Wed, 10 Feb 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab332
      Issue No: Vol. 504, No. 2 (2021)
  • Erratum: Characterization of V-type asteroids orbiting in the middle and
           outer main belt
    • Authors: Migliorini A; De Sanctis M, Michtchenko T, et al.
      Pages: 2033 - 2033
      Abstract: errata, addendatechniques: spectroscopictelescopesminor planets, asteroids: individual: Vesta
      PubDate: Wed, 28 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab908
      Issue No: Vol. 504, No. 2 (2021)
  • How does the mass and activity history of the host star affect the
           population of low-mass planets'
    • Authors: Kubyshkina D; Vidotto A.
      Pages: 2034 - 2050
      Abstract: ABSTRACTThe evolution of the atmospheres of low- and intermediate-mass planets is strongly connected to the physical properties of their host stars. The types and the past activities of planet-hosting stars can, therefore, affect the overall planetary population. In this paper, we perform a comparative study of sub-Neptune-like planets orbiting stars of different masses and different evolutionary histories. We discuss the general patterns of the evolved population as a function of parameters and environments of planets. As a model of the atmospheric evolution, we employ the own framework combining planetary evolution in Modules for Experiments in Stellar Astrophysics (mesa) with the realistic prescription of the escape of hydrogen-dominated atmospheres. We find that the final populations look qualitatively similar in terms of the atmospheres survival around different stars, but qualitatively different, with this difference accentuated for planets orbiting more massive stars. We show that a planet has larger chances of keeping its primordial atmosphere in the habitable zone of a solar-mass star compared to M or K dwarfs and if it starts the evolution having a relatively compact envelope. We also address the problem of the uncertain initial temperatures (luminosities) of planets and show that this issue is only of particular importance for planets exposed to extreme atmospheric mass losses.
      PubDate: Sat, 27 Mar 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab897
      Issue No: Vol. 504, No. 2 (2021)
  • Metallicity-dependent wind parameter predictions for OB stars
    • Authors: Vink J; Sander A.
      Pages: 2051 - 2061
      Abstract: ABSTRACTMass-loss rates and terminal wind velocities are key parameters that determine the kinetic wind energy and momenta of massive stars. Furthermore, accurate mass-loss rates determine the mass and rotational velocity evolution of mass stars, and their fates as neutron stars and black holes in function of metallicity (Z). Here, we update our Monte Carlo mass-loss Recipe with new dynamically consistent computations of the terminal wind velocity – as a function of Z. These predictions are particularly timely as the Hubble Space Telescope Ultraviolet Legacy Library of Young Stars as Essential Standards (ULLYSES) project will observe ultraviolet spectra with blue-shifted P Cygni lines of hundreds of massive stars in the low-Z Large and Small Magellanic Clouds (SMC), as well as sub-SMC metallicity hosts. Around 35 000 K, we uncover a weak-wind ‘dip’ and we present diagnostics to investigate its physics with ULLYSES and X-Shooter data. We discuss how the dip may provide important information on wind-driving physics, and how this is of key relevance towards finding a new gold-standard for OB star mass-loss rates. For B supergiants below the Fe iv to iii bi-stability jump, the terminal velocity is found to be independent of Z and M, while the mass-loss rate still varies as $\dot{M} \propto Z^{0.85}$. For O-type stars above the bi-stability jump we, find a terminal-velocity dependence of $\mbox{$v _{\infty }$}\propto Z^{0.19}$ and the Z-dependence of the mass-loss rate is found to be as shallow as $\dot{M} \propto Z^{0.42}$, implying that to reproduce the ‘heavy’ black holes from LIGO/Virgo, the ‘low Z’ requirement becomes even more stringent than was previously anticipated.
      PubDate: Wed, 31 Mar 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab902
      Issue No: Vol. 504, No. 2 (2021)
  • Extracting the 21 cm EoR signal using MWA drift scan data
    • Authors: Patwa A; Sethi S, Dwarakanath K.
      Pages: 2062 - 2072
      Abstract: ABSTRACTThe detection of redshifted hyperfine line of neutral hydrogen (H i) is the most promising probe of the epoch of reionization (EoR). We report an analysis of 55 h of Murchison Widefield Array (MWA) phase II drift scan EoR data. The data correspond to a central frequency $\nu _0 = 154.24 \, \rm MHz$ (z ≃ 8.2 for the redshifted H i hyperfine line) and bandwidth $B = 10.24 \, \rm MHz$. As one expects greater system stability in a drift scan, we test the system stability by comparing the extracted power spectra from data with noise simulations and show that the power spectra for the cleanest data behave as thermal noise. We compute the H i power spectrum as a function of time in one and two dimensions. The best upper limit on the 1D power spectrum are: $\Delta ^2(k) \simeq (1000~\rm mK)^2$ at k ≃ 0.2h Mpc−1 and at k ≃ 1h Mpc−1. The cleanest modes, which might be the most suited for obtaining the optimal signal to noise, correspond to k ≳ 1h Mpc−1. We also study the time-dependence of the foreground-dominated modes in a drift scan and compare with the expected behaviour.
      PubDate: Sat, 10 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab989
      Issue No: Vol. 504, No. 2 (2021)
  • A cool and inflated progenitor candidate for the Type Ib supernova 2019yvr
           at 2.6 yr before explosion
    • Authors: Kilpatrick C; Drout M, Auchettl K, et al.
      Pages: 2073 - 2093
      Abstract: ABSTRACTWe present Hubble Space Telescope imaging of a pre-explosion counterpart to SN 2019yvr obtained 2.6 yr before its explosion as a type Ib supernova (SN Ib). Aligning to a post-explosion Gemini-S/GSAOI image, we demonstrate that there is a single source consistent with being the SN 2019yvr progenitor system, the second SN Ib progenitor candidate after iPTF13bvn. We also analysed pre-explosion Spitzer/Infrared Array Camera (IRAC) imaging, but we do not detect any counterparts at the SN location. SN 2019yvr was highly reddened, and comparing its spectra and photometry to those of other, less extinguished SNe Ib we derive $E(B-V)=0.51\substack{+0.27\\-0.16}$ mag for SN 2019yvr. Correcting photometry of the pre-explosion source for dust reddening, we determine that this source is consistent with a log (L/L⊙) = 5.3 ± 0.2 and $T_{\mathrm{eff}} = 6800\substack{+400\\-200}$ K star. This relatively cool photospheric temperature implies a radius of 320$\substack{+30\\-50}~\mathrm{ R}_{\odot}$, much larger than expectations for SN Ib progenitor stars with trace amounts of hydrogen but in agreement with previously identified SN IIb progenitor systems. The photometry of the system is also consistent with binary star models that undergo common envelope evolution, leading to a primary star hydrogen envelope mass that is mostly depleted but still seemingly in conflict with the SN Ib classification of SN 2019yvr. SN 2019yvr had signatures of strong circumstellar interaction in late-time (>150 d) spectra and imaging, and so we consider eruptive mass-loss and common envelope evolution scenarios that explain the SN Ib spectroscopic class, pre-explosion counterpart, and dense circumstellar material. We also hypothesize that the apparent inflation could be caused by a quasi-photosphere formed in an extended, low-density envelope, or circumstellar matter around the primary star.
      PubDate: Tue, 30 Mar 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab838
      Issue No: Vol. 504, No. 2 (2021)
  • Search for dormant black holes in ellipsoidal variables – II. A binary
           modified minimum mass ratio
    • Authors: Gomel R; Faigler S, Mazeh T.
      Pages: 2115 - 2121
      Abstract: ABSTRACTThis is the second of a series of papers that focuses on searching large sets of photometric light curves for evidence of close binaries with a dormant black hole, and, in some cases, a dormant neutron star. The detection of such a binary is based on identifying a star that displays a large ellipsoidal periodic modulation, induced by tidal interaction with its companion. Based on the observed ellipsoidal amplitude and the primary mass and radius, one can derive a minimum mass ratio of the binary. A binary with a minimum mass ratio significantly larger than unity might be a candidate for having a dormant compact-object companion. Unfortunately, the photometric search is hampered by the fact that in many cases the primary mass and radius are not well known. In this paper we present a simple approach that circumvents this problem by suggesting a robust modified minimum mass ratio, assuming the primary fills its Roche lobe. The newly defined modified minimum mass ratio is always smaller than the minimum mass ratio, which is, in its turn, smaller than the actual mass ratio. Therefore, binaries with a modified minimum mass ratio larger than unity are candidates for having a compact-object secondary.
      PubDate: Thu, 15 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1047
      Issue No: Vol. 504, No. 2 (2021)
  • The symbiotic recurrent nova V3890 Sgr: binary parameters and
           pre-outburst activity
    • Authors: Mikołajewska J; Iłkiewicz K, Gałan C, et al.
      Pages: 2122 - 2132
      Abstract: ABSTRACTWe present and analyse optical photometry and high-resolution Southern African Large Telescope spectra of the symbiotic recurrent nova V3890 Sgr at quiescence. The orbital period, P = 747.6 d, has been derived from both photometric and spectroscopic data. Our double-line spectroscopic orbits indicate that the mass ratio is q = Mg/MWD = 0.78 ± 0.05, and that the component masses are MWD ≈ 1.35 ± 0.13 M⊙ and Mg ≈ 1.05 ± 0.11 M⊙. The orbit inclination is ≈67−69○. The red giant is filling (or nearly filling) its Roche lobe, and the distance set by its Roche lobe radius, d ≈ 9 kpc, is consistent with that resulting from the giant pulsation period. The outburst magnitude of V3890 Sgr is then very similar to those of RNe in the Large Magellanic Cloud. V3890 Sgr shows remarkable photometric and spectroscopic activity between the nova eruptions with time-scales similar to those observed in the symbiotic recurrent novae T CrB and RS Oph and Z And-type symbiotic systems. The active source has a double-temperature structure that we have associated with the presence of an accretion disc. The activity would be then caused by changes in the accretion rate. We also provide evidence that V3890 Sgr contains a CO WD accreting at a high, ∼a few× 10−8 to 10−7 M⊙ yr−1, rate. The WD is growing in mass, and should give rise to a Type Ia supernova within ≲106 yr – the expected lifetime of the red giant.
      PubDate: Fri, 16 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1058
      Issue No: Vol. 504, No. 2 (2021)
  • The dust mass in Cassiopeia A from infrared and optical line flux
    • Authors: Niculescu-Duvaz M; Barlow M, Bevan A, et al.
      Pages: 2133 - 2145
      Abstract: ABSTRACTThe large quantities of dust that have been found in a number of high-redshift galaxies have led to suggestions that core-collapse supernovae (CCSNe) are the main sources of their dust and have motivated the measurement of the dust masses formed by local CCSNe. For Cassiopeia A (Cas A), an oxygen-rich remnant of a Type IIb CCSN, a dust mass of 0.6–1.1 M⊙ has already been determined by two different methods, namely (a) from its far-infrared spectral energy distribution and (b) from analysis of the red–blue emission line asymmetries in its integrated optical spectrum. We present a third, independent, method for determining the mass of dust contained within Cas A. This compares the relative fluxes measured in similar apertures from [O iii] far-infrared and visual-region emission lines, taking into account foreground dust extinction, in order to determine internal dust optical depths, from which corresponding dust masses can be obtained. Using this method, we determine a dust mass within Cas A of at least 0.99$^{+0.10}_{-0.09}$ M⊙.
      PubDate: Wed, 07 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab932
      Issue No: Vol. 504, No. 2 (2021)
  • Recovering the origins of the lenticular galaxy NGC 3115 using multiband
    • Authors: Buzzo M; Cortesi A, Hernandez-Jimenez J, et al.
      Pages: 2146 - 2167
      Abstract: ABSTRACTA detailed study of the morphology of lenticular galaxies is an important way to understand how this type of galaxy is formed and evolves over time. Decomposing a galaxy into its components (disc, bulge, bar, ...) allows recovering the colour gradients present in each system, its star formation history, and its assembly history. We use galfitm to perform a multiwavelength structural decomposition of the closest lenticular galaxy, NGC 3115, resulting in the description of its stellar light into several main components: a bulge, a thin disc, a thick disc, and also evidence of a bar. We report the finding of central bluer stellar populations in the bulge, as compared to the colour of the galaxy outskirts, indicating either the presence of an active galactic nucleus (AGN) and/or recent star formation activity. From the spectral energy distribution results, we show that the galaxy has a low luminosity AGN component, but even excluding the effect of the nuclear activity, the bulge is still bluer than the outer-regions of the galaxy, revealing a recent episode of star formation. Based on all of the derived properties, we propose a scenario for the formation of NGC 3115 consisting of an initial gas-rich merger, followed by accretions and feedback that quench the galaxy, until a recent encounter with the companion KK084 that reignited the star formation in the bulge, provoked a core displacement in NGC 3115 and generated spiral-like features. This result is consistent with the two-phase formation scenario, proposed in previous studies of this galaxy.
      PubDate: Thu, 15 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab941
      Issue No: Vol. 504, No. 2 (2021)
  • Physical origin of the non-physical spin evolution of MAXI
           J1820 + 070
    • Authors: Guan J; Tao L, Qu J, et al.
      Pages: 2168 - 2180
      Abstract: ABSTRACTWe report on the Insight-HXMT observations of the new black hole X-ray binary MAXI J1820+070 during its 2018 outburst. Detailed spectral analysis via the continuum fitting method shows an evolution of the inferred spin during its high soft sate. Moreover, the hardness ratio, the non-thermal luminosity and the reflection fraction also undergo an evolution, exactly coincident to the period when the inferred spin transition takes place. The unphysical evolution of the spin is attributed to the evolution of the inner disc, which is caused by the collapse of a hot corona due to condensation mechanism or may be related to the deceleration of a jet-like corona. The studies of the inner disc radius and the relation between the disc luminosity and the inner disc radius suggest that, only at a particular epoch, did the inner edge of the disc reach the innermost stable circular orbit and the spin measurement is reliable. We then constrain the spin of MAXI J1820 + 070 to be $a_*=0.2^{+0.2}_{-0.3}$. Such a slowly spinning black hole possessing a strong jet suggests that its jet activity is driven mainly by the accretion disc rather than by the black hole spin.
      PubDate: Tue, 06 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab945
      Issue No: Vol. 504, No. 2 (2021)
  • Organic residues in astrophysical ice analogues: Thermal processing of
           hydrogenated glyoxal ices under interstellar conditions
    • Authors: Leroux K; Guillemin J, Krim L.
      Pages: 2181 - 2189
      Abstract: ABSTRACTOrganic residues are considered as part of the chemical composition of the interstellar dust grains. They are formed under the extreme conditions of the interstellar medium and play an important role in exobiology. They may contain pre-biotic organic species such as amino acids, constituents of proteins and building blocks of DNA and RNA, key elements of life. By investigating the formation of organic residues in an astrophysical context, many groups have been focusing in the UV irradiation and subsequent warm-up of astrophysical ice analogues. This aims to suggest that organic residues are mainly formed in regions of molecular clouds exposed to UV light or cosmic rays. This study shows an organic residue formation involving glyoxal ice and H atoms. While the hydrogenation of glyoxal at 10 K leads mainly to small molecules such as CO and H2CO and CH3OH, we show that the heating of the hydrogenated ice in the 10–300 K temperature range leads to solid residues whose structure is similar to that of glycolaldehyde but they remain stable in solid phase at 300 K and atmospheric pressure. The analysis of the IR data shows that the organic residues formed through the thermal processing of CHOCHO + H reaction would be a mixture of hydroxypyruvaldehyde and methyl glyoxylate, two solid organics whose formation starts with an H-abstraction from glyoxal to form CHOCO• radical which recombines to •CH2OH and •OCH3 radicals. These latter may be formed and trapped in glyoxal ice as secondary products from H2CO + H secondary reaction.
      PubDate: Wed, 14 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab951
      Issue No: Vol. 504, No. 2 (2021)
  • Fingerprints of stellar populations in the near-infrared: an optimized set
           of spectral indices in the JHK bands 0
    • Authors: Eftekhari E; Vazdekis A, La Barbera F.
      Pages: 2190 - 2223
      Abstract: ABSTRACTStellar population studies provide unique clues to constrain galaxy formation models. So far, detailed studies based on absorption line strengths have mainly focused on the optical spectral range although many diagnostic features are present in other spectral windows. In particular, the near-infrared (NIR) can provide a wealth of information about stars, such as evolved giants, that have less evident optical signatures. Due to significant advances in NIR instrumentation and extension of spectral libraries and stellar population synthesis (SPS) models to this domain, it is now possible to perform in-depth studies of spectral features in the NIR to a high level of precision. In this work, taking advantage of state-of-the-art SPS models covering the NIR spectral range, we introduce a new set of NIR indices constructed to be maximally sensitive to the main stellar population parameters, namely age, metallicity, and initial mass function (IMF). We fully characterize the new indices against these parameters as well as their sensitivity to individual elemental abundance variations, velocity dispersion broadening, wavelength shifts, signal-to-noise ratio, and flux calibration. We also present, for the first time, a method to ensure that the analysis of spectral indices is not affected by sky contamination, which is a major challenge when dealing with NIR spectroscopy. Moreover, we discuss two main applications: (i) the ability of some NIR spectral indices to constrain the shape of the low-mass IMF and (ii) current issues in the analysis of NIR spectral indices for future developments of SPS modelling.
      PubDate: Sat, 10 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab976
      Issue No: Vol. 504, No. 2 (2021)
  • The impact of line-of-sight structures on measuring H0 with strong lensing
           time delays
    • Authors: Li N; Becker C, Dye S.
      Pages: 2224 - 2234
      Abstract: ABSTRACTMeasurements of the Hubble–Lemaitre constant from early- and local-Universe observations show a significant discrepancy. In an attempt to understand the origin of this mismatch, independent techniques to measure H0 are required. One such technique, strong lensing time delays, is set to become a leading contender amongst the myriad methods due to forthcoming large strong lens samples. It is therefore critical to understand the systematic effects inherent in this method. In this paper, we quantify the influence of additional structures along the line of sight by adopting realistic light-cones derived from the cosmoDC2 semi-analytical extragalactic catalogue. Using multiple-lens plane ray tracing to create a set of simulated strong lensing systems, we have investigated the impact of line-of-sight structures on time-delay measurements and in turn, on the inferred value of H0. We have also tested the reliability of existing procedures for correcting for line-of-sight effects. We find that if the integrated contribution of the line-of-sight structures is close to a uniform mass sheet, the bias in H0 can be adequately corrected by including a constant external convergence κext in the lens model. However, for realistic line-of-sight structures comprising many galaxies at different redshifts, this simple correction overestimates the bias by an amount that depends linearly on the median external convergence. We therefore conclude that lens modelling must incorporate multiple-lens planes to account for line-of-sight structures for accurate and precise inference of H0.
      PubDate: Tue, 13 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab984
      Issue No: Vol. 504, No. 2 (2021)
  • On dust evolution in planet-forming discs in binary systems – I.
           Theoretical and numerical modelling: radial drift is faster in binary
    • Authors: Zagaria F; Rosotti G, Lodato G.
      Pages: 2235 - 2252
      Abstract: ABSTRACTMany stars are in binaries or higher order multiple stellar systems. Although in recent years a large number of binaries have been proven to host exoplanets, how planet formation proceeds in multiple stellar systems has not been studied much yet from the theoretical standpoint. In this paper, we focus on the evolution of the dust grains in planet-forming discs in binaries. We take into account the dynamics of gas and dust in discs around each component of a binary system under the hypothesis that the evolution of the circumprimary and the circumsecondary discs is independent. It is known from previous studies that the secular evolution of the gas in binary discs is hastened due to the tidal interactions with their hosting stars. Here, we prove that binarity affects dust dynamics too, possibly in a more dramatic way than the gas. In particular, the presence of a stellar companion significantly reduces the amount of solids retained in binary discs because of a faster, more efficient radial drift, ultimately shortening their lifetime. We prove that how rapidly discs disperse depends both on the binary separation, with discs in wider binaries living longer, and on the disc viscosity. Although the less-viscous discs lose high amounts of solids in the earliest stages of their evolution, they are dissipated slowly, while those with higher viscosities show an opposite behaviour. The faster radial migration of dust in binary discs has a striking impact on planet formation, which seems to be inhibited in this hostile environment, unless other disc substructures halt radial drift further in. We conclude that if planetesimal formation were viable in binary discs, this process would take place on very short time-scales.
      PubDate: Sat, 10 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab985
      Issue No: Vol. 504, No. 2 (2021)
  • Towards a better understanding of supernova environments: a study of
           SNe 2004dg and 2012P in NGC 5806 with HST and MUSE
    • Authors: Sun N; Maund J, Crowther P, et al.
      Pages: 2253 - 2272
      Abstract: ABSTRACTCore-collapse supernovae (SNe) are the inevitable fate of most massive stars. Since most stars form in groups, SN progenitors can be constrained with information of their environments. It remains challenging to accurately analyse the various components in the environment and to correctly identify their relationships with the SN progenitors. Using a combined data set of VLT/MUSE spatially resolved integral field unit (IFU) spectroscopy and HST/ACS+WFC3 high-spatial-resolution imaging, we present a detailed investigation of the environment of the Type II-P SN 2004dg and Type IIb SN 2012P. The two SNe occurred in a spiral arm of NGC 5806, where a star-forming complex is apparent with a giant H ii region. By modelling the ionized gas, a compact star cluster and the resolved stars, we derive the ages and extinctions of stellar populations in the vicinity of the SNe. The various components are consistent with a sequence of triggered star formation as the spiral density wave swept through their positions. For SNe 2004dg and 2012P, we identify their host stellar populations and derive initial masses of $10.0^{+0.3}_{-0.2}$ and $15.2^{+2.0}_{-1.0}$ M⊙ for their progenitors, respectively. Both results are consistent with those from pre-explosion images or nebular-phase spectroscopy. SN 2012P is spatially coincident but less likely to be coeval with the star-forming complex. As in this case, star formation bursts on small scales may appear correlated if they are controlled by any physical processes on larger scales; this may lead to a high probability of chance alignment between older SN progenitors and younger stellar populations.
      PubDate: Mon, 12 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab994
      Issue No: Vol. 504, No. 2 (2021)
  • Fundamental properties of stars from Kepler and Gaia data: parallax offset
           and revised scaling relations
    • Authors: Yıldız M; Örtel S.
      Pages: 2273 - 2285
      Abstract: ABSTRACTData from the space missions Gaia, Kepler, CoRoT and TESS, make it possible to compare parallax and asteroseismic distances. From the ratio of two densities ρsca/ρπ, we obtain an empirical relation fΔν between the asteroseismic large frequency separation and mean density, which is important for more accurate stellar mass and radius. This expression for main-sequence (MS) and subgiant stars with K-band magnitude is very close to the one obtained from interior MS models by Yıldız, Çelik & Kayhan. We also discuss the effects of effective temperature and parallax offset as the source of the difference between asteroseismic and non-asteroseismic stellar parameters. We have obtained our best results for about 3500 red giants (RGs) by using 2MASS data and model values for fΔν from Sharma et al. Another unknown scaling parameter $f_{\nu _{\rm max}}$ comes from the relationship between the frequency of maximum amplitude and gravity. Using different combinations of $f_{\nu _{\rm max}}$ and the parallax offset, we find that the parallax offset is generally a function of distance. The situation where this slope disappears is accepted as the most reasonable solution. By a very careful comparison of asteroseismic and non-asteroseismic parameters, we obtain very precise values for the parallax offset and $f_{\nu _{\rm max}}$ for RGs of –0.0463 ± 0.0007 mas and 1.003 ± 0.001, respectively. Our results for mass and radius are in perfect agreement with those of APOKASC-2: the mass and radius of ∼3500 RGs are in the range of about 0.8–1.8 M⊙ (96 per cent) and 3.8–38 R⊙, respectively.
      PubDate: Thu, 29 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab996
      Issue No: Vol. 504, No. 2 (2021)
  • sMILES: a library of semi-empirical MILES stellar spectra with variable
           [α/Fe] abundances
    • Authors: Knowles A; Sansom A, Allende Prieto C, et al.
      Pages: 2286 - 2311
      Abstract: ABSTRACTWe present a new library of semi-empirical stellar spectra that is based on the empirical Medium resolution Isaac Newton Library of Empirical Spectra (MILES) library. A new, high-resolution library of theoretical stellar spectra is generated that is specifically designed for use in stellar population studies. We test these models across their full wavelength range against other model libraries and find reasonable agreement in their predictions of spectral changes due to atmospheric α-element variations, known as differential corrections. We also test the models against the MILES and MaStar libraries of empirical stellar spectra and also find reasonable agreements, as expected from previous work. We then use the abundance pattern predictions of the new theoretical stellar spectra to differentially correct MILES spectra to create semi-empirical MILES (sMILES) star spectra with abundance patterns that differ from those present in the Milky Way. The final result is five families of 801 sMILES stars with [α/Fe] abundances ranging from −0.20 to 0.60 dex at MILES resolution (FWHM = $2.5\,$Å) and wavelength coverage ($3540.5\!-\!7409.6\,$Å). We make the sMILES library publicly available.
      PubDate: Sat, 10 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1001
      Issue No: Vol. 504, No. 2 (2021)
  • VLBI images at 327 MHz of compact steep spectrum and GHz-peaked spectrum
           sources from the 3C and PW samples
    • Authors: Dallacasa D; Orienti M, Fanti C, et al.
      Pages: 2312 - 2324
      Abstract: ABSTRACTWe present results on global very long baseline interferometry (VLBI) observations at 327 MHz of 18 compact steep-spectrum (CSS) and GHz-peaked spectrum (GPS) radio sources from the 3C and the Peacock & Wall catalogues. About 80 per cent of the sources have a ‘double/triple’ structure. The radio emission at 327 MHz is dominated by steep-spectrum extended structures, while compact regions become predominant at higher frequencies. As a consequence, we could unambiguously detect the core region only in three sources, likely due to self-absorption affecting its emission at this low frequency. Despite their low surface brightness, lobes store the majority of the source energy budget, whose correct estimate is a key ingredient in tackling the radio source evolution. Low-frequency VLBI observations able to disentangle the lobe emission from that of other regions are therefore the best way to infer the energetics of these objects. Dynamical ages estimated from energy budget arguments provide values between 2 × 103 and 5 × 104 yr, in agreement with the radiative ages estimated from the fit of the integrated synchrotron spectrum, further supporting the youth of these objects. A discrepancy between radiative and dynamical ages is observed in a few sources where the integrated spectrum is dominated by hotspots. In this case the radiative age likely represents the time spent by the particles in these regions, rather than the source age.
      PubDate: Tue, 13 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1014
      Issue No: Vol. 504, No. 2 (2021)
  • Modelling H2 and its effects on star formation using a joint
           implementation of gadget-3 and KROME
    • Authors: Sillero E; Tissera P, Lambas D, et al.
      Pages: 2325 - 2345
      Abstract: ABSTRACTWe present p-gadget3-k, an updated version of gadget-3, that incorporates the chemistry package krome. p-gadget3-k follows the hydrodynamical and chemical evolution of cosmic structures, incorporating the chemistry and cooling of H2 and metal cooling in non-equilibrium. We performed different runs of the same ICs to assess the impact of various physical parameters and prescriptions, namely gas metallicity, molecular hydrogen formation on dust, star formation recipes including or not H2 dependence, and the effects of numerical resolution. We find that the characteristics of the simulated systems, both globally and at kpc-scales, are in good agreement with several observable properties of molecular gas in star-forming galaxies. The surface density profiles of star formation rate (SFR) and H2 are found to vary with the clumping factor and resolution. In agreement with previous results, the chemical enrichment of the gas component is found to be a key ingredient to model the formation and distribution of H2 as a function of gas density and temperature. A star formation algorithm that takes into account the H2 fraction together with a treatment for the local stellar radiation field improves the agreement with observed H2 abundances over a wide range of gas densities and with the molecular Kennicutt–Schmidt law, implying a more realistic modelling of the star formation process.
      PubDate: Thu, 15 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1015
      Issue No: Vol. 504, No. 2 (2021)
  • Cosmological magnetogenesis: the Biermann battery during the Epoch of
    • Authors: Attia O; Teyssier R, Katz H, et al.
      Pages: 2346 - 2359
      Abstract: ABSTRACTWe investigate the effect of the Biermann battery during the Epoch of reionization (EoR) using cosmological Adaptive Mesh Refinement simulations within the framework of the sphinx project. We develop a novel numerical technique to solve for the Biermann battery term in the Constrained Transport method, preserving both the zero divergence of the magnetic field and the absence of Biermann battery for isothermal flows. The structure-preserving nature of our numerical method turns out to be very important to minimize numerical errors during validation tests of the propagation of a Str’omgren sphere and of a Sedov blast wave. We then use this new method to model the evolution of a 2.5 and 5 co-moving Mpc cosmological box with a state-of-the-art galaxy formation model within the Ramses code. Contrary to previous findings, we show that three different Biermann battery channels emerge: the first one is associated with linear perturbations before the EoR, the second one is the classical Biermann battery associated with reionization fronts during the EoR, and the third one is associated with strong, supernova-driven outflows. While the two former channels generate spontaneously volume-filling magnetic fields with a strength on the order or below 10−20 G, the latter, owing to the higher plasma temperature and a marginally resolved turbulent dynamo, reaches a field strength as high as 10−18 G in the intergalactic medium around massive haloes.
      PubDate: Thu, 15 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1030
      Issue No: Vol. 504, No. 2 (2021)
  • The Carbon-to-H2, CO-to-H2 conversion factors, and carbon abundance on
           kiloparsec scales in nearby galaxies
    • Authors: Jiao Q; Gao Y, Zhao Y.
      Pages: 2360 - 2380
      Abstract: ABSTRACTUsing the atomic carbon [C i] ($^{3} \rm P_{1} \rightarrow {\rm ^3 P}_{0}$) and [C i] ($^{3} \rm P_{2} \rightarrow {\rm ^3 P}_{1}$) emission {hereafter [C i] (1 − 0) and [C i] (2 − 1), respectively} maps observed with the Herschel Space Observatory, and CO (1 − 0), H i, infrared and submm maps from literatures, we estimate the [C i]-to-H2 and CO-to-H2 conversion factors of α[C i](1 − 0), α[C i](2 − 1), and αCO at a linear resolution $\sim 1\,$kpc scale for six nearby galaxies of M 51, M 83, NGC 3627, NGC 4736, NGC 5055, and NGC 6946. This is perhaps the first effort, to our knowledge, in calibrating both [C i]-to-H2 conversion factors across the spiral disks at spatially resolved $\sim 1\,$kpc scale though such studies have been discussed globally in galaxies near and far. In order to derive the conversion factors and achieve these calibrations, we adopt three different dust-to-gas ratio (DGR) assumptions that scale approximately with metallicity taken from precursory results. We find that for all DGR assumptions, the α[C i](1 − 0), α[C i](2 − 1), and αCO are mostly flat with galactocentric radii, whereas both α[C i](2 − 1) and αCO show decrease in the inner regions of galaxies. And the central αCO and α[C i](2 − 1) values are on average ∼2.2 and 1.8 times lower than its galaxy averages. The obtained carbon abundances from different DGR assumptions show flat profiles with galactocentric radii, and the average carbon abundance of the galaxies is comparable to the usually adopted value of 3 × 10−5. We find that both metallicity and infrared luminosity correlate moderately with the αCO, whereas only weakly with either the α[C i](1 − 0) or carbon abundance, and not at all with the α[C i](2 − 1).
      PubDate: Fri, 16 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1035
      Issue No: Vol. 504, No. 2 (2021)
  • Investigating the role of magnetic fields in star formation using
           molecular line profiles
    • Authors: Yin C; Priestley F, Wurster J.
      Pages: 2381 - 2389
      Abstract: ABSTRACTDetermining the importance of magnetic fields in star-forming environments is hampered by the difficulty of accurately measuring both field strength and gas properties in molecular clouds. We post-process three-dimensional non-ideal magnetohydrodynamic simulations of pre-stellar cores with a time-dependent chemical network, and use radiative transfer modelling to calculate self-consistent molecular line profiles. Varying the initial mass-to-flux ratio from subcritical to supercritical results in significant changes to both the intensity and shape of several observationally important molecular lines. We identify the peak intensity ratio of N2H+ to CS lines, and the CS J = 2–1 blue-to-red peak intensity ratio, as promising diagnostics of the initial mass-to-flux ratio, with N2H+/CS values of >0.6 (<0.2) and CS blue/red values of <3 (>5) indicating subcritical (supercritical) collapse. These criteria suggest that, despite presently being magnetically supercritical, L1498 formed from subcritical initial conditions.
      PubDate: Tue, 20 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1039
      Issue No: Vol. 504, No. 2 (2021)
  • Erratum: The double quasar Q2138-431: detection of a lensing galaxy
    • Authors: Hawkins M.
      Pages: 2390 - 2390
      Abstract: errata, addendagravitational lensing: strongquasars: individual (Q2138-431)
      PubDate: Fri, 30 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1104
      Issue No: Vol. 504, No. 2 (2021)
  • Evolving ultralight scalars into non-linearity with Lagrangian
           perturbation theory
    • Authors: Laguë A; Bond J, Hložek R, et al.
      Pages: 2391 - 2404
      Abstract: ABSTRACTMany models of high energy physics suggest that the cosmological dark sector consists of not just one, but a spectrum of ultralight scalar particles with logarithmically distributed masses. To study the potential signatures of low concentrations of ultralight axion (also known as fuzzy) dark matter, we modify Lagrangian perturbation theory (LPT) by distinguishing between trajectories of different dark matter species. We further adapt LPT to include the effects of a quantum potential, which is necessary to generate correct initial conditions for ultralight axion simulations. Based on LPT, our modified scheme is extremely efficient on large scales and it can be extended to an arbitrary number of particle species at very little computational cost. This allows for computation of self-consistent initial conditions in mixed dark matter models. Additionally, we find that shell-crossing is delayed for ultralight particles and that the deformation tensor extracted from LPT can be used to identify the range of redshifts and scales for which the Madelung formalism of fuzzy dark matter can lead to divergences.
      PubDate: Thu, 04 Mar 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab601
      Issue No: Vol. 504, No. 2 (2021)
  • Particle acceleration and magnetic field amplification in massive young
           stellar object jets
    • Authors: Araudo A; Padovani M, Marcowith A.
      Pages: 2405 - 2419
      Abstract: ABSTRACTSynchrotron radio emission from non-relativistic jets powered by massive protostars has been reported, indicating the presence of relativistic electrons and magnetic fields of strength ∼0.3–5 mG. We study diffusive shock acceleration and magnetic field amplification in protostellar jets with speeds between 300 and 1500 km s−1. We show that the magnetic field in the synchrotron emitter can be amplified by the non-resonant hybrid (Bell) instability excited by the cosmic ray streaming. By combining the synchrotron data with basic theory of Bell instability we estimate the magnetic field in the synchrotron emitter and the maximum energy of protons. Protons can achieve maximum energies in the range 0.04–0.65 TeV and emit γ rays in their interaction with matter fields. We predict detectable levels of γ rays in IRAS 16547−5247 and IRAS 16848−4603. The γ ray flux can be significantly enhanced by the gas mixing due to Rayleigh–Taylor instability. The detection of this radiation by the Fermi satellite in the GeV domain and the forthcoming Cherenkov Telescope Array at higher energies may open a new window to study the formation of massive stars, as well as diffusive acceleration and magnetic field amplification in shocks with velocities of about 1000 km s−1.
      PubDate: Fri, 19 Mar 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab635
      Issue No: Vol. 504, No. 2 (2021)
  • Towards a volumetric census of close white dwarf binaries – I.
           Reference samples
    • Authors: Inight K; Gänsicke B, Breedt E, et al.
      Pages: 2420 - 2442
      Abstract: ABSTRACTClose white dwarf binaries play an important role across a range of astrophysics, including thermonuclear supernovae, the Galactic low-frequency gravitational wave signal, and the chemical evolution of the Galaxy. Progress in developing a detailed understanding of the complex, multithreaded evolutionary pathways of these systems is limited by the lack of statistically sound observational constraints on the relative fractions of various sub-populations and their physical properties. The available samples are small, heterogeneous, and subject to a multitude of observational biases. Our overarching goal is to establish a volume-limited sample of all types of white dwarf binaries that is representative of the underlying population as well as sufficiently large to serve as a benchmark for future binary population models. In this first paper, we provide an overview of the project, and assemble reference samples within a distance limit of 300 pc of known white dwarf binaries spanning the most common sub-classes: post-common envelope binaries containing a white dwarf plus a main-sequence star, cataclysmic variables, and double-degenerate binaries. We carefully vet the members of these “Gold” samples, which span most of the evolutionary parameter space of close white dwarf binary evolution. We also explore the differences between magnitude and volume limited close white dwarf binary samples, and discuss how these systems evolve in their observational properties across the Gaia Hertzsprung–Russell diagram.
      PubDate: Tue, 16 Mar 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab753
      Issue No: Vol. 504, No. 2 (2021)
  • The impact of inhomogeneous subgrid clumping on cosmic reionization –
           II. Modelling stochasticity
    • Authors: Bianco M; Iliev I, Ahn K, et al.
      Pages: 2443 - 2460
      Abstract: ABSTRACTSmall-scale density fluctuations can significantly affect reionization, but are typically modelled quite crudely. Unresolved fluctuations in numerical simulations and analytical calculations are included using a gas clumping factor, typically assumed to be independent of the local environment. In Paper I, we presented an improved, local density-dependent model for the sub-grid gas clumping. Here, we extend this using an empirical stochastic model based on the results from high-resolution numerical simulations which fully resolve all relevant fluctuations. Our model reproduces well both the mean density-clumping relation and its scatter. We applied our stochastic model, along with the mean clumping one and the Paper I deterministic model, to create large-volume realizations of the clumping field, and used these in radiative transfer simulations of cosmic reionization. Our results show that the simplistic mean clumping model delays reionization compared to local density-dependent models, despite producing fewer recombinations overall. This is due to the very different spatial distribution of clumping, resulting in much higher photoionization rates in the latter cases. The mean clumping model produces smaller H ii regions throughout most of reionization, but those percolate faster at late times. It also causes a significant delay in the 21-cm fluctuations peak and yields lower non-Gaussianity and many fewer bright pixels in the PDF distribution. The stochastic density-dependent model shows relatively minor differences from the deterministic one, mostly concentrated around overlap, where it significantly suppresses the 21-cm fluctuations, and at the bright tail of the 21-cm PDFs, where it produces noticeably more bright pixels.
      PubDate: Wed, 24 Mar 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab787
      Issue No: Vol. 504, No. 2 (2021)
  • The surface magnetic activity of the weak-line T Tauri stars TWA 7 and TWA
    • Authors: Nicholson B; Hussain G, Donati J, et al.
      Pages: 2461 - 2473
      Abstract: ABSTRACTWe present an analysis of spectropolarimetric observations of the low-mass weak-line T Tauri stars TWA 25 and TWA 7. The large-scale surface magnetic fields have been reconstructed for both stars using the technique of Zeeman Doppler imaging. Our surface maps reveal predominantly toroidal and non-axisymmetric fields for both stars. These maps reinforce the wide range of surface magnetic fields that have been recovered, particularly in pre-main sequence stars that have stopped accreting from the (now depleted) central regions of their discs. We reconstruct the large scale surface brightness distributions for both stars, and use these reconstructions to filter out the activity-induced radial velocity jitter, reducing the RMS of the radial velocity variations from 495 to 32 m s −1 for TWA 25, and from 127 to 36 m s −1 for TWA 7, ruling out the presence of close-in giant planets for both stars. The TWA 7 radial velocities provide an example of a case where the activity-induced radial velocity variations mimic a Keplerian signal that is uncorrelated with the spectral activity indices. This shows the usefulness of longitudinal magnetic field measurements in identifying activity-induced radial velocity variations.
      PubDate: Fri, 26 Mar 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab879
      Issue No: Vol. 504, No. 2 (2021)
  • The effects of surface fossil magnetic fields on massive star evolution
           – III. The case of τ Sco
    • Authors: Keszthelyi Z; Meynet G, Martins F, et al.
      Pages: 2474 - 2492
      Abstract: ABSTRACTτ Sco, a well-studied magnetic B-type star in the Upper Sco association, has a number of surprising characteristics. It rotates very slowly and shows nitrogen excess. Its surface magnetic field is much more complex than a purely dipolar configuration which is unusual for a magnetic massive star. We employ the cmfgen radiative transfer code to determine the fundamental parameters and surface CNO and helium abundances. Then, we employ mesa and genec stellar evolution models accounting for the effects of surface magnetic fields. To reconcile τ Sco’s properties with single-star models, an increase is necessary in the efficiency of rotational mixing by a factor of 3–10 and in the efficiency of magnetic braking by a factor of 10. The spin-down could be explained by assuming a magnetic field decay scenario. However, the simultaneous chemical enrichment challenges the single-star scenario. Previous works indeed suggested a stellar merger origin for τ Sco. However, the merger scenario also faces similar challenges as our magnetic single-star models to explain τ Sco’s simultaneous slow rotation and nitrogen excess. In conclusion, the single-star channel seems less likely and versatile to explain these discrepancies, while the merger scenario and other potential binary-evolution channels still require further assessment as to whether they may self-consistently explain the observables of τ Sco.
      PubDate: Sat, 27 Mar 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab893
      Issue No: Vol. 504, No. 2 (2021)
  • Disc versus wind accretion in X-ray pulsar GX 301-2
    • Authors: Liu J; Ji L, Jenke P, et al.
      Pages: 2493 - 2500
      Abstract: ABSTRACTGX 301-2 provides a rare opportunity to study both disc and wind accretion in a same target. We report Insight-Hard X-ray Modulation Telescope observations of the spin-up event of GX 301-2 that happened in 2019 and compare with those of wind-fed state. The pulse profiles of the initial rapid spin-up period are dominated by one main peak, while those of the later slow spin-up period are composed of two similar peaks, as those of wind-fed state. These behaviours are confirmed by Fermi/Gamma-ray Burst Monitor data, which also show that during the rapid spin-up period, the main peak increases with luminosity up to 8 × 1037 erg s−1, but the faint peak remains almost constant. The absorption column densities during the spin-up period are ∼1.5 × 1023 cm−2, much less than those of wind-fed state at similar luminosity (∼9 × 1023 cm−2), supporting the scenario that most of material is condensed into a disc during the spin-up period. We discuss possible differences between disc and wind accretion that may explain the observed different trends of pulse profiles.
      PubDate: Mon, 05 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab938
      Issue No: Vol. 504, No. 2 (2021)
  • Imprints of the secondary interstellar hydrogen atoms at 1 au
    • Authors: Katushkina O; Baliukin I, Izmodenov V, et al.
      Pages: 2501 - 2508
      Abstract: ABSTRACTIn this paper, we search for the possible imprints of the secondary interstellar hydrogen atoms created at the heliospheric boundary in the full-sky maps of the hydrogen fluxes at the Earth orbit. By using our three-dimensional time-dependent kinetic model, the maps of the hydrogen fluxes are calculated for different phases of the solar cycle and different energy ranges. It is shown that the flux maps obtained during the solar minimum conditions for the energy range 1–20 eV have specific features such as blobs and tails, which are pronounced due to a signal of the secondary component of the interstellar atoms. We investigate how these features depend on parameters of the secondary atoms far away from the Sun and found that the geometry and shape of the tails depend on the averaged velocity and kinetic temperatures of the secondary population. The results of the paper provide a strategy where and when we need to look in order to detect the secondary component of the interstellar hydrogen separately from the primary component at 1 au. This can be important for future space missions devoted to the exploration of the heliospheric boundary.
      PubDate: Tue, 06 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab944
      Issue No: Vol. 504, No. 2 (2021)
  • Interpreting the variation phenomena of B2 1633+382 via the two-component
    • Authors: Wang Y; Jiang Y.
      Pages: 2509 - 2516
      Abstract: ABSTRACTBlazars are variable targets in the sky, whose variation mechanism remains an open question. In this work, we make a comprehensive study of the variation phenomena of the spectral index and polarization degree to deeply understand the variation mechanism of B2 1633+382 (4C 38.41). We use the local cross-correlation function to perform a correlation analysis between multiwavelength light curves. We find that both the γ-ray and the optical V band are correlated with the 15-GHz radio at beyond the 3σ confidence level. Based on the lag analysis, the emitting regions of the γ-ray and optical are located at $14.2_{-2.4}^{+0}$ and $14.2_{-8.3}^{+8.3}$ pc upstream of the core region of the15-GHz radio, and are far away from the broad-line region. The broad lines in the spectrum indicate the existence of an accretion disc component in the radiation. Thus, we consider a two-component model, which includes the relative constant background component and the varying jet component to study the variation behaviours. The Markov Chain Monte Carlo procedure is adopted to study the physical parameters of the jet and the background components. To some extent, the study of normalized residuals indicates that the two-component model fits better than the linear fitting model. The jet with a helical magnetic field is promising for explaining the variation, and the shock-in-jet model is not completely ruled out.
      PubDate: Thu, 08 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab963
      Issue No: Vol. 504, No. 2 (2021)
  • Unravelling the origin of magnetic fields in galaxies
    • Authors: Martin-Alvarez S; Katz H, Sijacki D, et al.
      Pages: 2517 - 2534
      Abstract: ABSTRACTDespite their ubiquity, there are many open questions regarding galactic and cosmic magnetic fields. Specifically, current observational constraints cannot rule out whether magnetic fields observed in galaxies were generated in the early Universe or are of astrophysical nature. Motivated by this, we use our magnetic tracer algorithm to investigate whether the signatures of primordial magnetic fields persist in galaxies throughout cosmic time. We simulate a Milky Way-like galaxy down to z ∼ 2–1 in four scenarios: magnetized solely by primordial magnetic fields, magnetized exclusively by supernova (SN)-injected magnetic fields, and two combined primordial + SN magnetization cases. We find that once primordial magnetic fields with a comoving strength B0 > 10−12 G are considered, they remain the primary source of galaxy magnetization. Our magnetic tracers show that, even combined with galactic sources of magnetization, when primordial magnetic fields are strong, they source the large-scale fields in the warm metal-poor phase of the simulated galaxy. In this case, the circumgalactic medium and intergalactic medium can be used to probe B0 without risk of pollution by magnetic fields originated in the galaxy. Furthermore, whether magnetic fields are primordial or astrophysically sourced can be inferred by studying local gas metallicity. As a result, we predict that future state-of-the-art observational facilities of magnetic fields in galaxies will have the potential to unravel astrophysical and primordial magnetic components of our Universe.
      PubDate: Fri, 09 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab968
      Issue No: Vol. 504, No. 2 (2021)
  • The first Hubble diagram and cosmological constraints using superluminous
    • Authors: Inserra C; Sullivan M, Angus C, et al.
      Pages: 2535 - 2549
      Abstract: ABSTRACTWe present the first Hubble diagram of superluminous supernovae (SLSNe) out to a redshift of two, together with constraints on the matter density, ΩM, and the dark energy equation-of-state parameter, w(≡p/ρ). We build a sample of 20 cosmologically useful SLSNe I based on light curve and spectroscopy quality cuts. We confirm the robustness of the peak–decline SLSN I standardization relation with a larger data set and improved fitting techniques than previous works. We then solve the SLSN model based on the above standardization via minimization of the χ2 computed from a covariance matrix that includes statistical and systematic uncertainties. For a spatially flat Λ cold dark matter (ΛCDM) cosmological model, we find $\Omega _{\rm M}=0.38^{+0.24}_{-0.19}$, with an rms of 0.27 mag for the residuals of the distance moduli. For a w0waCDM cosmological model, the addition of SLSNe I to a ‘baseline’ measurement consisting of Planck temperature together with Type Ia supernovae, results in a small improvement in the constraints of w0 and wa of 4 per cent. We present simulations of future surveys with 868 and 492 SLSNe I (depending on the configuration used) and show that such a sample can deliver cosmological constraints in a flat ΛCDM model with the same precision (considering only statistical uncertainties) as current surveys that use Type Ia supernovae, while providing a factor of 2–3 improvement in the precision of the constraints on the time variation of dark energy, w0 and wa. This paper represents the proof of concept for superluminous supernova cosmology, and demonstrates they can provide an independent test of cosmology in the high-redshift (z > 1) universe.
      PubDate: Fri, 09 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab978
      Issue No: Vol. 504, No. 2 (2021)
  • Analytical solutions for radiation-driven winds in massive stars –
           II. The δ-slow regime
    • Authors: Araya I; Christen A, Curé M, et al.
      Pages: 2550 - 2556
      Abstract: ABSTRACTAccurate mass-loss rates and terminal velocities from massive stars winds are essential to obtain synthetic spectra from radiative transfer calculations and to determine the evolutionary path of massive stars. From a theoretical point of view, analytical expressions for the wind parameters and velocity profile would have many advantages over numerical calculations that solve the complex non-linear set of hydrodynamic equations. In a previous work, we obtained an analytical description for the fast wind regime. Now, we propose an approximate expression for the line-force in terms of new parameters and obtain a velocity profile closed-form solution (in terms of the Lambert W function) for the δ-slow regime. Using this analytical velocity profile, we were able to obtain the mass-loss rates based on the m-CAK theory. Moreover, we established a relation between this new set of line-force parameters with the known stellar and m-CAK line-force parameters. To this purpose, we calculated a grid of numerical hydrodynamical models and performed a multivariate multiple regression. The numerical and our descriptions lead to good agreement between their values.
      PubDate: Sat, 10 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab995
      Issue No: Vol. 504, No. 2 (2021)
  • Testing the role of environmental effects on the initial mass function of
           low-mass stars
    • Authors: Damian B; Jose J, Samal M, et al.
      Pages: 2557 - 2576
      Abstract: ABSTRACTIn the star-formation process, the vital impact of environmental factors such as feedback from massive stars and stellar density on the form of the initial mass function (IMF) at the low-mass end is yet to be understood. Hence a systematic highly sensitive observational analysis of a sample of regions under diverse environmental conditions is essential. We analyse the IMF of eight young clusters (<5 Myr), namely IC 1848-West, IC 1848-East, NGC 1893, NGC 2244, NGC 2362, NGC 6611, Stock 8, and Cygnus OB2, which are located at the Galactocentric distance (Rg) range ∼6–12 kpc along with the nearby cluster IC 348 using deep near-IR photometry and Gaia DR2. These clusters are embedded in massive stellar environments of radiation strength $\log(L_\mathrm{FUV}/\mathrm{L}_{\odot })\, \sim 2.6$–6.8, $\log(L_\mathrm{EUV})\, \sim$ 42.2–50.85 photon s−1, with stellar density in the range of ∼170–1220 star pc−2. After structural analysis and field decontamination we obtain an unbiased uniformly sensitive sample of pre-main-sequence members of the clusters down to the brown-dwarf regime. The lognormal fit to the IMF of nine clusters gives the mean characteristic mass (mc) and σ of 0.32 ± 0.02 M⊙ and 0.47 ± 0.02, respectively. We compare the IMF with that of low- and high-mass clusters across the Milky Way. We also check for any systematic variation with respect to the radiation field strength and the stellar density as well with Rg. We conclude that there is no strong evidence for an environmental effect in the underlying form of the IMF of these clusters.
      PubDate: Sat, 01 May 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab194
      Issue No: Vol. 504, No. 2 (2021)
  • A unicorn in monoceros: the 3 M⊙ dark companion to the bright, nearby
           red giant V723 Mon is a non-interacting, mass-gap black hole candidate
    • Authors: Jayasinghe T; Stanek K, Thompson T, et al.
      Pages: 2577 - 2602
      Abstract: ABSTRACTWe report the discovery of the closest known black hole candidate as a binary companion to V723 Mon. V723 Mon is a nearby ($d\sim 460\, \rm pc$), bright (V ≃ 8.3 mag), evolved (Teff, giant ≃ 4440 K, and Lgiant ≃ 173 L⊙) red giant in a high mass function, f(M) = 1.72 ± 0.01 M⊙, nearly circular binary (P = 59.9 d, e ≃ 0). V723 Mon is a known variable star, previously classified as an eclipsing binary, but its All-Sky Automated Survey, Kilodegree Extremely Little Telescope, and Transiting Exoplanet Survey Satellite light curves are those of a nearly edge-on ellipsoidal variable. Detailed models of the light curves constrained by the period, radial velocities, and stellar temperature give an inclination of $87.0^{\circ ^{+1.7^\circ }}_{-1.4^\circ }$, a mass ratio of q ≃ 0.33 ± 0.02, a companion mass of Mcomp = 3.04 ± 0.06 M⊙, a stellar radius of Rgiant = 24.9 ± 0.7 R⊙, and a giant mass of Mgiant = 1.00 ± 0.07 M⊙. We identify a likely non-stellar, diffuse veiling component with contributions in the B and V band of ${\sim }63{{\ \rm per\ cent}}$ and ${\sim }24{{\ \rm per\ cent}}$, respectively. The SED and the absence of continuum eclipses imply that the companion mass must be dominated by a compact object. We do observe eclipses of the Balmer lines when the dark companion passes behind the giant, but their velocity spreads are low compared to observed accretion discs. The X-ray luminosity of the system is $L_{\rm X}\simeq 7.6\times 10^{29}~\rm ergs~s^{-1}$, corresponding to L/Ledd ∼ 10−9. The simplest explanation for the massive companion is a single compact object, most likely a black hole in the ‘mass gap’.
      PubDate: Sat, 01 May 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab907
      Issue No: Vol. 504, No. 2 (2021)
  • A generative model of galactic dust emission using variational
    • Authors: Thorne B; Knox L, Prabhu K.
      Pages: 2603 - 2613
      Abstract: ABSTRACTEmission from the interstellar medium can be a significant contaminant of measurements of the intensity and polarization of the cosmic microwave background (CMB). For planning CMB observations, and for optimizing foreground-cleaning algorithms, a description of the statistical properties of such emission can be helpful. Here, we examine a machine learning approach to inferring the statistical properties of dust from observational data. In particular, we apply a type of neural network called a variational autoencoder (VAE) to maps of the intensity of emission from interstellar dust as inferred from Planck sky maps and demonstrate its ability to (i) simulate new samples with similar summary statistics as the training set, (ii) provide fits to emission maps withheld from the training set, and (iii) produce constrained realizations. We find VAEs are easier to train than another popular architecture: that of generative adversarial networks, and are better suited for use in Bayesian inference.
      PubDate: Mon, 12 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1011
      Issue No: Vol. 504, No. 2 (2021)
  • Revisiting high-order Taylor methods for astrodynamics and celestial
    • Authors: Biscani F; Izzo D.
      Pages: 2614 - 2628
      Abstract: ABSTRACTWe present heyoka, a new, modern and general-purpose implementation of Taylor’s integration method for the numerical solution of ordinary differential equations. Detailed numerical tests focused on difficult high-precision gravitational problems in astrodynamics and celestial mechanics show how our general-purpose integrator is competitive with and often superior to state-of-the-art specialized symplectic and non-symplectic integrators in both speed and accuracy. In particular, we show how Taylor methods are capable of satisfying Brouwer’s law for the conservation of energy in long-term integrations of planetary systems over billions of dynamical time-scales. We also show how close encounters are modelled accurately during simulations of the formation of the Kirkwood gaps and of Apophis’ 2029 close encounter with the Earth (where heyoka surpasses the speed and accuracy of domain-specific methods). heyoka can be used from both C++ and python, and it is publicly available as an open-source project.
      PubDate: Thu, 15 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1032
      Issue No: Vol. 504, No. 2 (2021)
  • Resolved galactic superwinds reconstructed around their host galaxies at z
           &gt; 3
    • Authors: Chen M; Chen H, Gronke M, et al.
      Pages: 2629 - 2657
      Abstract: ABSTRACTThis paper presents a detailed analysis of two giant Lyman-alpha (Ly α) arcs detected near galaxies at z = 3.038 and z = 3.754 lensed by the massive cluster MACS 1206−0847 (z = 0.44). The Ly α nebulae revealed in deep MUSE observations exhibit a double-peaked profile with a dominant red peak, indicating expansion/outflowing motions. One of the arcs stretches over 1 arcmin around the cluster Einstein radius, resolving the velocity field of the line-emitting gas on kpc scales around three star-forming galaxies of 0.3–$1.6\, L_*$ at z = 3.038. The second arc spans 15 arcsec in size, roughly centred around two low-mass Ly α emitters of $\approx 0.03\, L_*$ at z = 3.754. All three galaxies in the z = 3.038 group exhibit prominent damped Ly α absorption (DLA) and several metal absorption lines, in addition to nebular emission lines such as $\hbox{He ii}$$\lambda \, 1640$ and C iii]λλ1906, 1908. Extended Ly α emission appears to emerge from star-forming regions with suppressed surface brightness at the centre of each galaxy. Significant spatial variations in the Ly α line profile are observed which, when unaccounted for in the integrated line, leads to biased constraints for the underlying gas kinematics. The observed spatial variations indicate the presence of a steep velocity gradient in a continuous flow of high column density gas from star-forming regions into a low-density halo environment. A detailed inspection of available galaxy spectra shows no evidence of AGN activity in the galaxies, and the observed Ly α signals are primarily explained by resonant scattering. The study presented in this paper shows that spatially resolved imaging spectroscopy provides the most detailed insights yet into the kinematics of galactic superwinds associated with star-forming galaxies.
      PubDate: Thu, 15 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1041
      Issue No: Vol. 504, No. 2 (2021)
  • An analytical model to kinematically identify thin discs in MaNGA galaxies
    • Authors: Yang M; Weijmans A, Bershady M, et al.
      Pages: 2658 - 2669
      Abstract: ABSTRACTWe present an analytical model to identify thin discs in galaxies, and apply this model to a sample of SDSS MaNGA galaxies. This model fits the velocity and velocity dispersion fields of galaxies with regular kinematics. By introducing two parameters ζ related to the comparison of the model’s asymmetric drift correction to the observed gas kinematics and η related to the dominant component of a galaxy, we classify the galaxies in the sample as ‘disc-dominated, ‘non-disc-dominated’, or ‘disc-free’ indicating galaxies with a dominating thin disc, a non-dominating thin disc, or no thin disc detection with our method, respectively. The dynamical mass resulting from our model correlates with stellar mass, and we investigate discrepancies by including gas mass and variation of the initial mass function. As expected, most spiral galaxies in the sample are disc-dominated, while ellipticals are predominantly disc-free. Lenticular galaxies show a dichotomy in their kinematic classification, which is related to their different star formation rates and gas fractions. We propose two possible scenarios to explain these results. In the first scenario, disc-free lenticulars formed in more violent processes than disc-dominated ones, while in the second scenario, the quenching processes in lenticulars lead to a change in their kinematic structures as disc-dominated lenticulars evolve to disc-free ones.
      PubDate: Thu, 15 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1049
      Issue No: Vol. 504, No. 2 (2021)
  • Post-merger evolution of double helium white dwarfs and distribution of
           helium-rich hot subdwarfs
    • Authors: Yu J; Zhang X, Lü G.
      Pages: 2670 - 2674
      Abstract: ABSTRACTThe mergers of double helium white dwarfs are believed to form isolated helium-rich hot subdwarfs. Observations show that helium-rich hot subdwarfs can be divided into two subgroups based on whether the surface is carbon-rich or carbon-normal. However, it is not clear whether this distribution directly comes from binary evolution. We adopt the binary population synthesis to obtain the population of single helium-rich hot subdwarfs according to the merger channel of double helium white dwarfs. We find that the merger channel can represent the two subgroups in the Teff−log g plane related to different masses of progenitor helium white dwarfs. For Z  = 0.02, the birth rate and local density of helium-rich hot subdwarf stars from the merger of two helium white dwarfs are $\sim 4.82 \times 10^{-3}\, \rm yr^{-1}$ and ∼ 290.0 $\rm kpc^{-3}$ at 13.7 Gyr in our Galaxy, respectively. The proportions of carbon-rich and carbon-normal helium-rich hot subdwarfs are 32 per cent and 68 per cent, respectively.
      PubDate: Sat, 01 May 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1063
      Issue No: Vol. 504, No. 2 (2021)
  • Radio properties of 10 nearby ultraluminous infrared galaxies with
           signatures of luminous buried active galactic nuclei
    • Authors: Hayashi T; Hagiwara Y, Imanishi M.
      Pages: 2675 - 2686
      Abstract: ABSTRACTWe present the results of our multifrequency observations for 10 ultraluminous infrared galaxies (ULIRGs) made by the Karl G. Jansky Very Large Array at 1.4, 5.5, 9.0, and 14.0 GHz. Our sample is selected from ULIRGs whose active galactic nuclei (AGNs) are not found at optical wavelengths (∼70 per cent of the total ULIRGs), but whose presence is suggested by mid-infrared or submillimetre observations (>50 per cent of the non-AGN ULIRGs at optical wavelengths). The statistical properties of the targets are similar to those of the entire ULIRG sample, which implies that ULIRGs have common radiative processes regardless of the presence of optical AGNs, and thus AGNs might equally contribute to the radio emission of every ULIRG. Although their spectra are mainly explained by starbursts and/or merger activity, some individual sources suggest contributions from AGNs. IRAS 00188−0856, whose optical morphology is not disturbed, shows a large non-thermal fraction and a spectral break at high frequency, which can be explained by synchrotron ageing of non-thermal plasma emitted from AGNs. In addition, we find 100-kpc-scale extended emission associated with IRAS 01004−2237. The two-sided morphology and absence of extended X-ray emission suggest that this system is not induced by a merger in a cluster but originates from AGN activity.
      PubDate: Sat, 01 May 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1084
      Issue No: Vol. 504, No. 2 (2021)
  • Morpho-kinematics of the circumstellar envelope of the AGB star R Dor: a
           global view
    • Authors: Nhung P; Hoai D, Tuan-Anh P, et al.
      Pages: 2687 - 2706
      Abstract: ABSTRACTWe analyse new ALMA observations of the 29SiO (ν = 0, J = 8–7) and SO2 (ν = 0, 343,31−342,32) line emissions of the circumstellar envelope (CSE) of the oxygen-rich asymptotic giant branch (AGB) star, R Dor. With a spatial resolution of ∼2.3 au, the observations cover distances below ∼30 au from the star providing a link between earlier observations and clarifying some open issues. The main conclusions are the following. (i) Rotation is confined below ∼15 au from the star, with velocity reaching a maximum below 10 au and morphology showing no significant disc-like flattening. (ii) In the south-eastern quadrant, a large Doppler velocity gas stream is studied in more detail than previously possible and its possible association with an evaporating planetary companion is questioned. (iii) A crude evaluation of the respective contributions of rotation, expansion and turbulence to the morpho-kinematics is presented. Significant line broadening occurs below ∼12 au from the star and causes the presence of high Doppler velocity components near the line of sight pointing to the centre of the star. (iv) Strong absorption of the continuum emission of the stellar disc and its immediate dusty environment is observed to extend beyond the disc in the form of self-absorption. The presence of a cold SiO layer extending up to some 60 au from the star is shown to be the cause. (v) Line emissions from SO, 28SiO, CO and HCN molecules are used to probe the CSE up to some 100 au from the star, revealing the presence of two broad back-to-back outflows, the morphology of which is studied in finer detail than in earlier work.
      PubDate: Sat, 01 May 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab954
      Issue No: Vol. 504, No. 2 (2021)
  • White dwarfs with planetary remnants in the era of Gaia – I. Six
           emission line systems
    • Authors: Gentile Fusillo N; Manser C, Gänsicke B, et al.
      Pages: 2707 - 2726
      Abstract: ABSTRACTWhite dwarfs with emission lines from gaseous debris discs are among the rarest examples of planetary remnant hosts, but at the same time they are key objects for studying the final evolutionary stage of planetary systems. Making use of the large number of white dwarfs identified in Gaia Data Release 2 (DR2), we are conducting a survey of planetary remnants and here we present the first results of our search: six white dwarfs with gaseous debris discs. This first publication focuses on the main observational properties of these objects and highlights their most unique features. Three systems in particular stand out: WD J084602.47+570328.64 displays an exceptionally strong infrared excess that defies the standard model of a geometrically thin, optically thick dusty debris disc; WD J213350.72+242805.93 is the hottest gaseous debris disc host known with $\mbox{$T_{\mathrm{eff}}$}=29\,282$ K; and WD J052914.32–340108.11 in which we identify a record number of 51 emission lines from five elements. These discoveries shed light on the underlying diversity in gaseous debris disc systems and bring the total number of these objects to 21. With these numbers we can now start looking at the properties of these systems as a class of objects rather than on a case-by-case basis.
      PubDate: Sat, 10 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab992
      Issue No: Vol. 504, No. 2 (2021)
  • The tidal stream generated by the globular cluster NGC 3201
    • Authors: Palau C; Miralda-Escudé J.
      Pages: 2727 - 2741
      Abstract: ABSTRACTWe detect a tidal stream generated by the globular cluster NGC 3201 extending over ∼140 deg on the sky, using the Gaia DR2 data, with the maximum-likelihood method we presented previously to study the M68 tidal stream. Most of the detected stream is the trailing one, which stretches in the southern Galactic hemisphere and passes within a close distance of 3.2 kpc from the Sun, therefore making the stream highly favourable for discovering relatively bright member stars, while the leading arm is further from us and behind a disc foreground that is harder to separate from. The cluster has just crossed the Galactic disc and is now in the northern Galactic hemisphere, moderately obscured by dust, and the part of the trailing tail closest to the cluster is highly obscured behind the plane. We obtain a best-fitting model of the stream which is consistent with the measured proper motion, radial velocity, and distance to NGC 3201, and show it to be the same as the previously detected Gjöll stream by Ibata et al. We identify ∼200 stars with the highest likelihood of being stream members using only their Gaia kinematic data. Most of these stars (170) are photometrically consistent with being members of NGC 3201 when they are compared to the cluster H–R diagram, only once a correction for dust absorption and reddening by the Galaxy is applied. The remaining stars are consistent with being random foreground objects according to simulated data sets. We list these 170 highly likely stream member stars.
      PubDate: Thu, 15 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1024
      Issue No: Vol. 504, No. 2 (2021)
  • The Hi-GAL compact source catalogue – II. The 360° catalogue of
           clump physical properties
    • Authors: Elia D; Merello M, Molinari S, et al.
      Pages: 2742 - 2766
      Abstract: ABSTRACTWe present the 360° catalogue of physical properties of Hi-GAL compact sources, detected between 70 and 500 $\mu$m. This release not only completes the analogous catalogue previously produced by the Hi-GAL collaboration for −71° ≲ ℓ ≲ 67°, but also meaningfully improves it because of a new set of heliocentric distances, 120 808 in total. About a third of the 150 223 entries are located in the newly added portion of the Galactic plane. A first classification based on detection at 70 $\mu$m as a signature of ongoing star-forming activity distinguishes between protostellar sources (23 per cent of the total) and starless sources, with the latter further classified as gravitationally bound (pre-stellar) or unbound. The integral of the spectral energy distribution, including ancillary photometry from λ = 21 to 1100 $\mu$m, gives the source luminosity and other bolometric quantities, while a modified blackbody fitted to data for $\lambda \ge 160~\mu$m yields mass and temperature. All tabulated clump properties are then derived using photometry and heliocentric distance, where possible. Statistics of these quantities are discussed with respect to both source Galactic location and evolutionary stage. No strong differences in the distributions of evolutionary indicators are found between the inner and outer Galaxy. However, masses and densities in the inner Galaxy are on average significantly larger, resulting in a higher number of clumps that are candidates to host massive star formation. Median behaviour of distance-independent parameters tracing source evolutionary status is examined as a function of the Galactocentric radius, showing no clear evidence of correlation with spiral arm positions.
      PubDate: Fri, 16 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1038
      Issue No: Vol. 504, No. 2 (2021)
  • A Chandra survey of z ≥ 4.5 quasars
    • Authors: Li J; Wang F, Yang J, et al.
      Pages: 2767 - 2782
      Abstract: ABSTRACTX-ray observations provide a unique probe of the accretion disc corona of supermassive black holes (SMBHs). In this paper, we present a uniform Chandra X-ray data analysis of a sample of 152 z ≥ 4.5 quasars. We firmly detect 46 quasars of this sample in 0.5–2 keV above 3σ and calculate the upper limits of the X-ray flux of the remaining. We also estimate the power-law photon index of the X-ray spectrum of 31 quasars. 24 of our sample quasars are detected in the FIRST or NVSS radio surveys; all of them are radio-loud. We statistically compare the X-ray properties of our z ≥ 4.5 quasars to other X-ray samples of active galactic nuclei (AGNs) at different redshifts. The relation between the rest-frame X-ray luminosity and other quasar parameters, such as the bolometric luminosity, UV luminosity, or SMBH mass, shows large scatters. These large scatters can be attributed to the narrow luminosity range at the highest redshift, the large measurement error based on relatively poor X-ray data, and the inclusion of radio-loud quasars in the sample. The LX–LUV relationship is significantly sublinear. We do not find a significant redshift evolution of the LX–LUV relation, expressed either in the slope of this relation, or the departure of individual AGNs from the best-fitting αOX–LUV relation (ΔαOX). The median value of the X-ray photon index is Γ ≈ 1.79, which does not show redshift evolution from z = 0 to z ∼ 7. The X-ray and UV properties of the most distant quasars could potentially be used as a standard candle to constrain cosmological models. The large scatter of our sample on the Hubble diagram highlights the importance of future large unbiased deep X-ray and radio surveys in using quasars in cosmological studies.
      PubDate: Thu, 15 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1042
      Issue No: Vol. 504, No. 2 (2021)
  • 3D simulations of photochemical hazes in the atmosphere of hot Jupiter
           HD 189733b
    • Authors: Steinrueck M; Showman A, Lavvas P, et al.
      Pages: 2783 - 2799
      Abstract: ABSTRACTPhotochemical hazes have been suggested as candidate for the high-altitude aerosols observed in the transmission spectra of many hot Jupiters. We present 3D simulations of the hot Jupiter HD 189733b to study how photochemical hazes are transported by atmospheric circulation. The model includes spherical, constant-size haze particles that gravitationally settle and are transported by the winds as passive tracers, with particle radii ranging from 1 nm to 1 $\mu$m. We identify two general types of haze distribution based on particle size: In the small-particle regime (<30 nm), gravitational settling is unimportant, and hazes accumulate in two large mid-latitude vortices centred on the nightside that extend across the morning terminator. Therefore, small hazes are more concentrated at the morning terminator than at the evening terminator. In the large-particle regime (>30 nm), hazes settle out quickly on the nightside, resulting in more hazes at the evening terminator. For small particles, terminator differences in haze mass mixing ratio and temperature considered individually can result in significant differences in the transit spectra of the terminators. When combining both effects for HD 189733b, however, they largely cancel out each other, resulting in very small terminator differences in the spectra. Transit spectra based on the GCM-derived haze distribution fail to reproduce the steep spectral slope at short wavelengths in the current transit observations of HD 189733b. Enhanced sub-grid scale mixing and/or optical properties of hazes differing from soot can explain the mismatch between the model and observations, although uncertainties in temperature and star spots may also contribute to the spectral slope.
      PubDate: Sat, 17 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1053
      Issue No: Vol. 504, No. 2 (2021)
  • Substructures in the core of Abell 2319
    • Authors: Ichinohe Y; Simionescu A, Werner N, et al.
      Pages: 2800 - 2810
      Abstract: ABSTRACTWe analysed the deep archival Chandra observations of the high-temperature galaxy cluster Abell 2319 to investigate the prominent cold front in its core. The main sharp arc of the front shows wiggles, or variations of the radius of the density jump along the arc. At the southern end of the arc is a feature that resembles a Kelvin–Helmholtz (KH) eddy, beyond which the sharp front dissolves. These features suggest that KH instabilities develop at the front. Under this assumption, we can place an upper limit on the ICM viscosity that is several times below the isotropic Spitzer value. Other features include a split of the cold front at its northern edge, which may be another KH eddy. There is a small pocket of hot, less-dense gas inside the cold front, which may indicate a ‘hole’ in the front’s magnetic insulation layer that lets the heat from the outer gas to penetrate inside the front. Finally, a large concave brightness feature south-west of the cluster core can be caused by the gas-dynamic instabilities. We speculate that it can also be an inner boundary of a giant AGN bubble, similar to that in Ophiuchus. If the latter interpretation is supported by better radio data, this could be a remnant of another extremely powerful AGN outburst.
      PubDate: Sat, 17 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1060
      Issue No: Vol. 504, No. 2 (2021)
  • Analytic expressions for geometric cross-sections of fractal dust
    • Authors: Tazaki R.
      Pages: 2811 - 2821
      Abstract: ABSTRACTIn protoplanetary discs and planetary atmospheres, dust grains coagulate to form fractal dust aggregates. The geometric cross-section of these aggregates is a crucial parameter characterizing aerodynamical friction, collision rates, and opacities. However, numerical measurements of the cross-section are often time consuming as aggregates exhibit complex shapes. In this study, we derive a novel analytic expression for geometric cross-sections of fractal aggregates. If an aggregate consists of N monomers of radius R0, its geometric cross-section G is expressed as $G=AN\pi R_0^2/[1+(N-1)\tilde{\sigma }]$, where $\tilde{\sigma }$ is an overlapping efficiency, and A is a numerical factor connecting the analytic expression to the small non-fractal cluster limit. The overlapping efficiency depends on the fractal dimension, fractal prefactor, and N of the aggregate, and its analytic expression is derived as well. The analytic expressions successfully reproduce numerically measured cross-sections of aggregates. We also find that our expressions are compatible with the mean-field light scattering theory of aggregates in the geometrical optics limit. The analytic expressions greatly simplify an otherwise tedious calculation and will be useful in model calculations of fractal grain growth in protoplanetary discs and planetary atmospheres.
      PubDate: Mon, 19 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1069
      Issue No: Vol. 504, No. 2 (2021)
  • Optimizing serendipitous detections of kilonovae: cadence and filter
    • Authors: Almualla M; Anand S, Coughlin M, et al.
      Pages: 2822 - 2831
      Abstract: ABSTRACTThe rise of multimessenger astronomy has brought with it the need to exploit all available data streams and learn more about the astrophysical objects that fall within its breadth. One possible avenue is the search for serendipitous optical/near-infrared counterparts of gamma-ray bursts (GRBs) and gravitational-wave (GW) signals, known as kilonovae. With surveys such as the Zwicky Transient Facility (ZTF), which observes the sky with a cadence of ∼3 d, the existing counterpart locations are likely to be observed; however, due to the significant amount of sky to explore, it is difficult to search for these fast-evolving candidates. Thus, it is beneficial to optimize the survey cadence for realtime kilonova identification and enable further photometric and spectroscopic observations. We explore how the cadence of wide field-of-view surveys like ZTF can be improved to facilitate such identifications. We show that with improved observational choices, e.g. the adoption of three epochs per night on a ∼ nightly basis, and the prioritization of redder photometric bands, detection efficiencies improve by about a factor of two relative to the nominal cadence. We also provide realistic hypothetical constraints on the kilonova rate as a form of comparison between strategies, assuming that no kilonovae are detected throughout the long-term execution of the respective observing plan. These results demonstrate how an optimal use of ZTF increases the likelihood of kilonova discovery independent of GWs or GRBs, thereby allowing for a sensitive search with less interruption of its nominal cadence through Target of Opportunity programs.
      PubDate: Mon, 19 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1090
      Issue No: Vol. 504, No. 2 (2021)
  • Numerical simulations of dark matter haloes produce polytropic central
           cores when reaching thermodynamic equilibrium
    • Authors: Sánchez Almeida J; Trujillo I.
      Pages: 2832 - 2840
      Abstract: ABSTRACTSelf-gravitating astronomical objects often show a central plateau in the density profile (core) whose physical origin is hotly debated. Cores are theoretically expected in N-body systems of maximum entropy, however, they are not present in the canonical N-body numerical simulations of cold dark matter (CDM). Our work shows that despite this apparent contradiction between theory and numerical simulations, they are fully consistent. Simply put, cores are characteristic of systems in thermodynamic equilibrium, but thermalizing collisions are purposely suppressed in CDM simulations. When collisions are allowed, N-body numerical simulations develop cored density profiles, in perfect agreement with the theoretical expectation. We compare theory and two types of numerical simulations: (1) when DM particles are self-interacting (SIDM) with enough cross-section, then the effective two-body relaxation time-scale becomes shorter than the Hubble time resulting in cored DM haloes. The haloes thus obtained, with masses from dwarf galaxies to galaxy clusters, collapse to a single shape after normalization, and this shape agrees with the polytropic density profile theoretically expected. (2) The inner radii in canonical N-body numerical simulations are always discarded because the use of finite-mass DM particles artificially increases the two-body collision rate. We show that the discarded radii develop cores which are larger than the employed numerical softening and have polytropic shape independently of halo mass. Our work suggests that the presence of cores in simulated (or observed) density profiles can used as evidence for systems in thermodynamic equilibrium.
      PubDate: Wed, 21 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1103
      Issue No: Vol. 504, No. 2 (2021)
  • Erratum: Relaxation of spherical stellar systems
    • Authors: Lau J; Binney J.
      Pages: 2841 - 2841
      Abstract: ABSTRACTWe present corrected versions of two figures in Lau & Binney (2019) and explain why the originals were incorrect.
      PubDate: Tue, 04 May 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1111
      Issue No: Vol. 504, No. 2 (2021)
  • Evidence of chromospheric molecular hydrogen emission in a solar flare
           observed by the IRIS satellite
    • Authors: Mulay S; Fletcher L.
      Pages: 2842 - 2852
      Abstract: ABSTRACTWe have carried out the first comprehensive investigation of enhanced line emission from molecular hydrogen, H2 at 1333.79 Å, observed at flare ribbons in SOL2014-04-18T13:03. The cool H2 emission is known to be fluorescently excited by Si iv 1402.77 Å UV radiation and provides a unique view of the temperature minimum region (TMR). Strong H2 emission was observed when the Si iv 1402.77 Å emission was bright during the flare impulsive phase and gradual decay phase, but it dimmed during the GOES peak. H2 line broadening showed non-thermal speeds in the range 7–18 $\rm {km\,s}^{-1}$, possibly corresponding to turbulent plasma flows. Small red (blue) shifts, up to 1.8 (4.9) $\rm {km\,s}^{-1}$ were measured. The intensity ratio of Si iv 1393.76 Å and Si iv 1402.77 Å confirmed that plasma was optically thin to Si iv (where the ratio = 2) during the impulsive phase of the flare in locations where strong H2 emission was observed. In contrast, the ratio differs from optically thin value of 2 in parts of ribbons, indicating a role for opacity effects. A strong spatial and temporal correlation between H2 and Si iv emission was evident supporting the notion that fluorescent excitation is responsible.
      PubDate: Fri, 12 Feb 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab367
      Issue No: Vol. 504, No. 2 (2021)
  • Bayesian constraints on the origin and geology of exoplanetary material
           using a population of externally polluted white dwarfs
    • Authors: Harrison J; Bonsor A, Kama M, et al.
      Pages: 2853 - 2867
      Abstract: ABSTRACTWhite dwarfs that have accreted planetary bodies are a powerful probe of the bulk composition of exoplanetary material. In this paper, we present a Bayesian model to explain the abundances observed in the atmospheres of 202 DZ white dwarfs by considering the heating, geochemical differentiation, and collisional processes experienced by the planetary bodies accreted, as well as gravitational sinking. The majority (>60 per cent) of systems are consistent with the accretion of primitive material. We attribute the small spread in refractory abundances observed to a similar spread in the initial planet-forming material, as seen in the compositions of nearby stars. A range in Na abundances in the pollutant material is attributed to a range in formation temperatures from below 1000 K to higher than 1400 K, suggesting that pollutant material arrives in white dwarf atmospheres from a variety of radial locations. We also find that Solar System-like differentiation is common place in exoplanetary systems. Extreme siderophile (Fe, Ni, or Cr) abundances in eight systems require the accretion of a core-rich fragment of a larger differentiated body to at least a 3σ significance, whilst one system shows evidence that it accreted a crust-rich fragment. In systems where the abundances suggest that accretion has finished (13/202), the total mass accreted can be calculated. The 13 systems are estimated to have accreted masses ranging from the mass of the Moon to half that of Vesta. Our analysis suggests that accretion continues for 11 Myrs on average.
      PubDate: Thu, 25 Mar 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab736
      Issue No: Vol. 504, No. 2 (2021)
  • Wave dark matter and ultra-diffuse galaxies
    • Authors: Pozo A; Broadhurst T, de Martino I, et al.
      Pages: 2868 - 2876
      Abstract: ABSTRACTDark matter (DM) as a Bose–Einstein condensate, such as the axionic scalar field particles of String Theory, can explain the coldness of DM on large scales. Pioneering simulations in this context predict a rich wave-like structure, with a ground state soliton core in every galaxy surrounded by a halo of excited states that interfere on the de Broglie scale. This de Broglie scale is largest for the low-mass galaxies as momentum is lower, providing a simple explanation for the wide cores of dwarf spheroidal galaxies. Here we extend these ‘wave dark matter’ (ψDM) predictions to the newly discovered class of ‘ultra-diffuse galaxies’ (UDG) that resemble dwarf spheroidal galaxies but with more extended stellar profiles. Currently, the best-studied example, ‘Dragon Fly 44’ (DF44), has a uniform velocity dispersion of ≃33 km s−1, extending to at least 3 kpc, that we show is reproduced by our ψDM simulations with a soliton radius of ≃0.5 kpc. In the ψDM context, we show that relatively flat dispersion profile of DF44 lies between massive galaxies with compact dense solitons, as may be present in the Milky Way on a scale of 100 pc and lower mass galaxies where the velocity dispersion declines centrally within a wide, low-density soliton, like Antlia II, of radius 3 kpc.
      PubDate: Fri, 26 Mar 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab855
      Issue No: Vol. 504, No. 2 (2021)
  • AB Aurigae: possible evidence of planet formation through the
           gravitational instability
    • Authors: Cadman J; Rice K, Hall C.
      Pages: 2877 - 2888
      Abstract: ABSTRACTRecent observations of the protoplanetary disc surrounding AB Aurigae have revealed the possible presence of two giant planets in the process of forming. The young measured age of 1–4 Myr for this system allows us to place strict time constraints on the formation histories of the observed planets. Hence, we may be able to make a crucial distinction between formation through core accretion (CA) or the gravitational instability (GI), as CA formation time-scales are typically Myr whilst formation through GI will occur within the first ≈104–105 yr of disc evolution. We focus our analysis on the 4–13MJup planet observed at R ≈ 30 au. We find CA formation time-scales for such a massive planet typically exceed the system’s age. The planet’s high mass and wide orbit may instead be indicative of formation through GI. We use smoothed particle hydrodynamic simulations to determine the system’s critical disc mass for fragmentation, finding Md,crit = 0.3 M⊙. Viscous evolution models of the disc’s mass history indicate that it was likely massive enough to exceed Md,crit in the recent past; thus, it is possible that a young AB Aurigae disc may have fragmented to form multiple giant gaseous protoplanets. Calculations of the Jeans mass in an AB Aurigae-like disc find that fragments may initially form with masses 1.6–13.3MJup, consistent with the planets that have been observed. We therefore propose that the inferred planets in the disc surrounding AB Aurigae may be evidence of planet formation through GI.
      PubDate: Tue, 06 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab905
      Issue No: Vol. 504, No. 2 (2021)
  • Large dust fractions can prevent the propagation of soundwaves
    • Authors: David-Cléris T; Laibe G.
      Pages: 2889 - 2894
      Abstract: ABSTRACTDust plays a central role in several astrophysical processes. Hence, the need of dust/gas numerical solutions, and analytical problems to benchmark them. In the seminal dustywave problem, we discover a regime where sound waves cannot propagate through the mixture above a large critical dust fraction. We characterize this regime analytically, making it of use for testing accuracy of numerical solvers at large dust fractions.
      PubDate: Mon, 05 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab931
      Issue No: Vol. 504, No. 2 (2021)
  • Long-term measurements of the erosion and accretion of dust deposits on
           comet 67P/Churyumov–Gerasimenko with the OSIRIS instrument
    • Authors: Cambianica P; Cremonese G, Fulle M, et al.
      Pages: 2895 - 2910
      Abstract: ABSTRACTWe monitor the seasonal erosion and accretion of dust deposits in the Imhotep, Hatmehit, and Ma’at regions of comet 67P/Churyumov–Gerasimenko with OSIRIS Narrow Angle Camera images. The vertical accuracy of such measurements is 0.2 m and the spatial scale of the images we used is lower than 0.60 m pixel−1. We calculate the height of 21 boulders by applying a tool that allows to measure the shadow length of a boulder projected on the surrounding dust deposit, assuming that any height variation is not due to boulder intrinsic change. Any boulder height variation provides a direct measurement about the thickness variation of the surrounding dust layer due to the occurring erosion and/or accretion. The analysis concerns the period from 2014 August, inbound to perihelion, to 2016 September, outbound. We measured the erosion in the Ma’at region of 0.6 ± 0.2 m from 2014 September 12 to December 2, and an erosion of 0.4 ± 0.3 m from 2014 December 3 to 2015 February 15. Then, we measured a dust deposition of 0.7 ± 0.3 m during the following perihelion phase, until 2016 May–September. This result confirms the link between the erosion of the Southern hemisphere and the fallout in the northern regions. The Imhotep and Hatmehit regions are characterized by a negligible erosion during the inbound orbit, consistent with pebble-made nucleus models predicting no erosion when the temperature of the nucleus surface is Ts < 205 K.
      PubDate: Fri, 09 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab950
      Issue No: Vol. 504, No. 2 (2021)
  • Cosmological cross-correlations and nearest neighbour distributions
    • Authors: Banerjee A; Abel T.
      Pages: 2911 - 2923
      Abstract: ABSTRACTCross-correlations between data sets are used in many different contexts in cosmological analyses. Recently, k-nearest neighbour cumulative distribution functions (kNN-CDF) were shown to be sensitive probes of cosmological (auto) clustering. In this paper, we extend the framework of NN measurements to describe joint distributions of, and correlations between, two data sets. We describe the measurement of joint kNN-CDFs, and show that these measurements are sensitive to all possible connected N-point functions that can be defined in terms of the two data sets. We describe how the cross-correlations can be isolated by combining measurements of the joint kNN-CDFs and those measured from individual data sets. We demonstrate the application of these measurements in the context of Gaussian density fields, as well as for fully non-linear cosmological data sets. Using a Fisher analysis, we show that measurements of the halo-matter cross-correlations, as measured through NN measurements are more sensitive to the underlying cosmological parameters, compared to traditional two-point cross-correlation measurements over the same range of scales. Finally, we demonstrate how the NN cross-correlations can robustly detect cross-correlations between sparse samples – the same regime where the two-point cross-correlation measurements are dominated by noise.
      PubDate: Thu, 22 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab961
      Issue No: Vol. 504, No. 2 (2021)
  • A MeerKAT view on galaxy clusters: a radio–optical study of Abell 1300
           and MACS J1931.8−2634
    • Authors: Terni de Gregory B; Hugo B, Venturi T, et al.
      Pages: 2924 - 2939
      Abstract: ABSTRACTIn this paper, we present results from a radio–optical study of the galaxy populations of the galaxy clusters Abell 1300 and MACS J1931.8−2634, a merger and a relaxed system respectively both located at z ∼ 0.3, aimed at finding evidence of merger-induced radio emission. Radio observations are taken at 1.28 GHz with the MeerKAT interferometer during its early-stage commissioning phase, and combined with archive optical data. We generated catalogues containing 107 and 162 radio sources in the A 1300 and MACS J1931.8−2634 cluster fields, respectively, above a 0.2 mJy threshold and within a 30 arcmin radius from the cluster centre (corresponding to 8.1 and 8.8 Mpc, respectively). By cross-correlating the radio and optical catalogues, and including spectroscopic information, nine and six sources were found to be cluster members and used to construct the radio luminosity functions, respectively, for both clusters. The comparison of the radio source catalogues between the two cluster fields leads to a marginal difference, with a 2σ statistical significance. We derived the radio luminosity function at 1.28 GHz in both clusters, in the power range of $22.81 \lt \rm {log~\mathit{ P}_{1.28~GHz}~(W\,Hz^{-1})} \lt 25.95$, and obtained that in A 1300 the radio luminosity function averaged over the full radio power interval is only 3.3 ± 1.9 times higher than the MACS J1931.8−2634 one, suggesting no statistical difference in their probability to host nuclear radio emission. We conclude that, at least for the two clusters studied here, the role of cluster mergers in affecting the statistical properties of the radio galaxy population is negligible.
      PubDate: Fri, 09 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab964
      Issue No: Vol. 504, No. 2 (2021)
  • Magnetohydrodynamic convection in accretion discs
    • Authors: Held L; Latter H.
      Pages: 2940 - 2960
      Abstract: ABSTRACTConvection has been discussed in the field of accretion discs for several decades, both as a means of angular momentum transport and also because of its role in controlling discs’ vertical structure via heat transport. If the gas is sufficiently ionized and threaded by a weak magnetic field, convection might interact in non-trivial ways with the magnetorotational instability (MRI). Recently, vertically stratified local simulations of the MRI have reported considerable variation in the angular momentum transport, as measured by the stress to thermal pressure ratio α, when convection is thought to be present. Although MRI turbulence can act as a heat source for convection, it is not clear how the two instabilities will interact dynamically. Here, we investigate their interplay in controlled numerical experiments and isolate the generic features of their interactions. We perform vertically stratified, 3D magnetohydrodynamic shearing box simulations with a perfect gas equation of state with the conservative, finite-volume code pluto. We find two characteristic outcomes of the interaction between the two instabilities: (a) straight MRI and (b) MRI/convective cycles, with the latter exhibiting alternating phases of convection-dominated and MRI-dominated flow. During the latter phase, we find that α is enhanced by nearly an order of magnitude, reaching peak values of ∼0.08. In addition, we find that convection in the non-linear phase takes the form of large-scale and oscillatory convective cells. Convection can also help the MRI persist to lower Rm than it would otherwise do. Finally, we discuss how our results help interpret simulations of dwarf novae.
      PubDate: Mon, 12 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab974
      Issue No: Vol. 504, No. 2 (2021)
  • Compton scattering in the optically thick uniform spherical corona around
           the neutron star in an X-ray binary in two conditions
    • Authors: Shi C.
      Pages: 2961 - 2967
      Abstract: ABSTRACTWe consider the Compton scattering in the optically thick uniform spherical corona around a neutron star in an X-ray binary. In the scattering, the low energy seed photons (0.1 ∼ 2.5 keV) are scattered in low energy electrons (2.5 ∼ 10 keV) in the corona in two conditions, i.e. initial seed photons are scattered in a whole corona and scattered in every layer of the corona that are supposed to be divided into many layers. When the same number of input seed photons, the same corona parameters, and the same energy distribution of all photons in the two conditions are considered, the approximately same number of output photons can be obtained, which means that there is approximately a transform invariance of layering the Comptonized corona. Thus the scattering in the layers of a multilayered corona is approximately equal to the scattering in the whole corona by dividing the whole corona into several layers. It means that Compton scattering for the initial seed photons scattered in a whole optically thick spherical corona with uniformly distributed electrons also can be considered as that the multiple Compton scatterings take place in the layers of a multilayered corona in order approximately, which can be used to explore some physical process in one part of a corona.
      PubDate: Thu, 15 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab993
      Issue No: Vol. 504, No. 2 (2021)
  • The VMC Survey – XL. Three-dimensional structure of the Small Magellanic
           Cloud as derived from red clump stars
    • Authors: Tatton B; van Loon J, Cioni M, et al.
      Pages: 2983 - 2997
      Abstract: ABSTRACTGalaxy interactions distort the distribution of baryonic matter and can affect star formation. The nearby Magellanic Clouds are a prime example of an ongoing galaxy interaction process. Here, we use the intermediate-age (∼1–10 Gyr) red clump (RC) stars to map the 3D structure of the Small Magellanic Cloud (SMC) and interpret it within the context of its history of interaction with the Large Magellanic Cloud (LMC) and the Milky Way. RC stars are selected from near-infrared colour–magnitude diagrams based on data from the Visible and Infrared Survey Telescope for Astronomy survey of the Magellanic Clouds. Interstellar reddening is measured and removed, and the corrected brightness is converted to a distance, on a star-by-star basis. A flat plane fitted to the spatial distribution of RC stars has an inclination i = 35°–48° and position angle, PA=170°–186°. However, significant deviations from this plane are seen, especially in the periphery and on the eastern side of the SMC. In the latter part, two distinct populations are present, separated in distance by as much as 10 kpc. Distant RC stars are seen in the north of the SMC, and possibly also in the far west; these might be associated with the predicted ‘Counter-Bridge’. We also present a dust reddening map, which shows that dust generally traces stellar mass. The structure of the intermediate-age stellar component of the SMC bears the imprints of strong interaction with the LMC a few Gyr ago, which cannot be purely tidal but must have involved ram pressure stripping.
      PubDate: Mon, 03 May 2021 00:00:00 GMT
      DOI: 10.1093/mnras/staa3857
      Issue No: Vol. 504, No. 2 (2021)
  • I – A hydrodynamical clone of the Virgo cluster of galaxies to confirm
           observationally driven formation scenarios
    • Authors: Sorce J; Dubois Y, Blaizot J, et al.
      Pages: 2998 - 3012
      Abstract: ABSTRACTAt ∼16–17 Mpc from us, the Virgo cluster is a formidable source of information to study cluster formation and galaxy evolution in rich environments. Several observationally driven formation scenarios arose within the past decade to explain the properties of galaxies that entered the cluster recently and the nature of the last significant merger that the cluster underwent. Confirming these scenarios requires extremely faithful numerical counterparts of the cluster. This paper presents the first clone, Constrained LOcal and Nesting Environment, simulation of the Virgo cluster within a ∼15 Mpc radius sphere. This cosmological hydrodynamical simulation, with feedback from supernovae and active galactic nuclei, with a ∼3 × 107 M⊙ dark matter particle mass and a minimum cell size of 350 pc in the zoom region, reproduces Virgo within its large-scale environment unlike a random cluster simulation. Overall the distribution of the simulated galaxy population matches the observed one including M87. The simulated cluster formation reveals exquisite agreements with observationally driven scenarios: within the last Gyr, about 300 small galaxies (M* > 107 M⊙) entered the cluster, most of them within the last 500 Myr. The last significant merger event occurred about 2 Gyr ago: a group with a tenth of the mass of today’s cluster entered from the far side as viewed from the Milky Way. This excellent numerical replica of Virgo will permit studying different galaxy type evolution (jellyfish, backsplash, etc.) as well as feedback phenomena in the cluster core via unbiased comparisons between simulated and observed galaxies and hot gas phase profiles to understand this great physics laboratory.
      PubDate: Thu, 15 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1021
      Issue No: Vol. 504, No. 2 (2021)
  • A kinematic analysis of ionized extraplanar gas in the spiral galaxies NGC
           3982 and NGC 4152
    • Authors: Li A; Marasco A, Fraternali F, et al.
      Pages: 3013 - 3028
      Abstract: ABSTRACTWe present a kinematic study of ionized extraplanar gas in two low-inclination late-type galaxies (NGC 3982 and NGC 4152) using integral field spectroscopy data from the DiskMass H α sample. We first isolate the extraplanar gas emission by masking the H α flux from the regularly rotating disc. The extraplanar gas emission is then modelled in the 3D position–velocity domain using a parametric model described by three structural and four kinematic parameters. Best-fitting values for the model are determined via a Bayesian MCMC approach. The reliability and accuracy of our modelling method are carefully determined via tests using mock data. We detect ionized extraplanar gas in both galaxies, with scale heights $0.83^{+0.27}_{-0.40}\, \mathrm{kpc}$ (NGC 3982) and $1.87^{+0.43}_{-0.56}\, \mathrm{kpc}$ (NGC 4152) and flux fraction between the extraplanar gas and the regularly rotating gas within the disc of 27 and 15 per cent, respectively, consistent with previous determinations in other systems. We find lagging rotation of the ionized extraplanar gas in both galaxies, with vertical rotational gradients $-22.24^{+6.60}_{-13.13} \, \mathrm{km\, s^{-1}\, kpc^{-1}}$ and $-11.18^{+3.49}_{-4.06}\, \mathrm{km\, s^{-1}\, kpc^{-1}}$, respectively, and weak evidence for vertical and radial inflow in both galaxies. The above results are similar to the kinematics of the neutral extraplanar gas found in several galaxies, though this is the first time that 3D kinematic modelling of ionized extraplanar gas has been carried out. Our results are broadly consistent with a galactic fountain origin combined with gas accretion. However, a dynamical model is required to better understand the formation of ionized extraplanar gas.
      PubDate: Thu, 15 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1043
      Issue No: Vol. 504, No. 2 (2021)
  • Optimizing high-redshift galaxy surveys for environmental information
    • Authors: Looser T; Lilly S, Sin L, et al.
      Pages: 3029 - 3057
      Abstract: ABSTRACTWe investigate the performance of group finding algorithms that reconstruct galaxy groups from the positional information of tracer galaxies that are observed in redshift surveys carried out with multiplexed spectrographs. We use mock light-cones produced by the L-Galaxies semi-analytic model of galaxy evolution in which the underlying reality is known. We particularly focus on the performance at high redshift, and how this is affected by choices of the mass of the tracer galaxies (largely equivalent to their co-moving number density) and the (assumed random) sampling rate of these tracers. We first however compare two different approaches to group finding as applied at low redshift, and conclude that these are broadly comparable. For simplicity we adopt just one of these, ‘Friends-of-Friends’ (FoF) as the basis for our study at high redshift. We introduce 12 science metrics that are designed to quantify the performance of the group-finder as relevant for a wide range of science investigations with a group catalogue. These metrics examine the quality of the recovered group catalogue, the median halo masses of different richness structures, the scatter in dark matter halo mass and how successful the group-finder classifies singletons, centrals, and satellites. We analyse how these metrics vary with the limiting stellar mass and random sampling rate of the tracer galaxies, allowing quantification of the various trade-offs between different possible survey designs. Finally, we look at the impact of these same design parameters on the relative ‘costs’ in observation time of the survey using as an example the potential MOONRISE survey using the MOONS instrument.
      PubDate: Wed, 21 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1061
      Issue No: Vol. 504, No. 2 (2021)
  • The origin of bulges and discs in the CALIFA survey – I.
           Morphological evolution
    • Authors: Méndez-Abreu J; de Lorenzo-Cáceres A, Sánchez S.
      Pages: 3058 - 3073
      Abstract: ABSTRACTThis series of papers aims at understanding the formation and evolution of non-barred disc galaxies. We use the new spectro-photometric decomposition code, c2d, to separate the spectral information of bulges and discs of a statistically representative sample of galaxies from the CALIFA survey. Then, we study their stellar population properties analysing the structure-independent datacubes with the Pipe3D algorithm. We find a correlation between the bulge-to-total (B/T) luminosity (and mass) ratio and galaxy stellar mass. The B/T mass ratio has only a mild evolution with redshift, but the bulge-to-disc (B/D) mass ratio shows a clear increase of the disc component since redshift z < 1 for massive galaxies. The mass–size relation for both bulges and discs describes an upturn at high galaxy stellar masses (log (M⋆/M⊙) > 10.5). The relation holds for bulges but not for discs when using their individual stellar masses. We find a negligible evolution of the mass–size relation for both the most massive ($\log {(M_{\star \rm ,b,d}/{\rm M}_{\odot })} \gt 10$) bulges and discs. For lower masses, discs show a larger variation than bulges. We also find a correlation between the Sérsic index of bulges and both galaxy and bulge stellar mass, which does not hold for the disc mass. Our results support an inside-out formation of nearby non-barred galaxies, and they suggest that (i) bulges formed early-on and (ii) they have not evolved much through cosmic time. However, we find that the early properties of bulges drive the future evolution of the galaxy as a whole, and particularly the properties of the discs that eventually form around them.
      PubDate: Wed, 21 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1064
      Issue No: Vol. 504, No. 2 (2021)
  • An HST/STIS view of protoplanetary discs in Upper Scorpius:
           observations of three young M stars
    • Authors: Walker S; Millar-Blanchaer M, Ren B, et al.
      Pages: 3074 - 3083
      Abstract: ABSTRACTWe present observations of three protoplanetary discs in visible scattered light around M-type stars in the Upper Scorpius OB association using the Space Telescope Imaging Spectrograph (STIS) instrument on the Hubble Space Telescope (HST). The discs around stars 2MASS J16090075–1908526, 2MASS J16142029–1906481, and 2MASS J16123916–1859284 have all been previously detected with the Atacama Large Millimeter/submillimeter Array (ALMA), and 2MASS J16123916–1859284 has never previously been imaged at scattered light wavelengths. We process our images using reference star differential imaging, comparing and contrasting three reduction techniques – classical subtraction, Karhunen–Loève Image Projection, and non-negative matrix factorization, selecting the classical method as the most reliable of the three for our observations. Of the three discs, two are tentatively detected (2MASS J16142029–1906481 and 2MASS J16123916–1859284), with the third going undetected. Our two detections are shown to be consistent when varying the reference star or reduction method used, and both detections exhibit structure out to projected distances of ≳200 au. Structures at these distances from the host star have never been previously detected at any wavelength for either disc, illustrating the utility of visible-wavelength observations in probing the distribution of small dust grains at large angular separations.
      PubDate: Sat, 17 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1080
      Issue No: Vol. 504, No. 2 (2021)
  • A machine learning approach for GRB detection in AstroSat CZTI data
    • Authors: Abraham S; Mukund N, Vibhute A, et al.
      Pages: 3084 - 3091
      Abstract: ABSTRACTWe present a machine learning (ML) based method for automated detection of Gamma-Ray Burst (GRB) candidate events in the range 60–250 keV from the AstroSat Cadmium Zinc Telluride Imager data. We use density-based spatial clustering to detect excess power and carry out an unsupervised hierarchical clustering across all such events to identify the different light curves present in the data. This representation helps us to understand the instrument’s sensitivity to the various GRB populations and identify the major non-astrophysical noise artefacts present in the data. We use Dynamic Time Warping (DTW) to carry out template matching, which ensures the morphological similarity of the detected events with known typical GRB light curves. DTW alleviates the need for a dense template repository often required in matched filtering like searches. The use of a similarity metric facilitates outlier detection suitable for capturing previously unmodelled events. We briefly discuss the characteristics of 35 long GRB candidates detected using the pipeline and show that with minor modifications such as adaptive binning, the method is also sensitive to short GRB events. Augmenting the existing data analysis pipeline with such ML capabilities alleviates the need for extensive manual inspection, enabling quicker response to alerts received from other observatories such as the gravitational-wave detectors.
      PubDate: Mon, 19 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1082
      Issue No: Vol. 504, No. 2 (2021)
  • Measurement on the cosmic curvature using the Gaussian process method
    • Authors: Yang Y; Gong Y.
      Pages: 3092 - 3097
      Abstract: ABSTRACTInflation predicts that the Universe is spatially flat. The Planck 2018 measurements of the cosmic microwave background anisotropy favour a spatially closed universe at more than 2σ confidence level. We use model-independent methods to study the issue of cosmic curvature. The method reconstructs the Hubble parameter H(z) from cosmic chronometers data with the Gaussian process method. The distance modulus is then calculated with the reconstructed function H(z) and fitted by Type Ia supernovae data. Combining the cosmic chronometers and Type Ia supernovae data, we obtain Ωk0h2 = 0.102 ± 0.066 that is consistent with a spatially flat universe at the 2σ confidence level. By adding the redshift-space distortions data to the Type Ia supernovae data with a proposed novel model-independent method, we obtain $\Omega _{k0}h^2=0.117^{+0.058}_{-0.045}$ and no deviation from Λ cold dark matter (ΛCDM) model is found.
      PubDate: Wed, 19 May 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab1085
      Issue No: Vol. 504, No. 2 (2021)
  • The nature of the Eastern Extent in the outer halo of M31
    • Authors: Preston J; Collins M, Rich R, et al.
      Pages: 3098 - 3110
      Abstract: ABSTRACTWe present the first comprehensive spectroscopic study of the Andromeda galaxy’s Eastern Extent. This ∼4° long filamentary structure, located 70–90 kpc from the centre of M31, lies perpendicular to Andromeda’s minor axis and the Giant Stellar Stream and overlaps Stream C. In this work, we explore the properties of the Eastern Extent to look for possible connections between it, the Giant Stellar Stream and Stream C. We present the kinematics and photometry for ∼50 red giant branch stars in seven fields along the Eastern Extent. We measure the systemic velocities for these fields and find them to be −368  km s−1 ≲ $\textit {v}$ ≲ −331  km s−1, with a slight velocity gradient of −0.51 ± 0.21  km s−1 kpc−1 towards the Giant Stellar Stream. We derive the photometric metallicities for stars in the Eastern Extent, finding them to be metal-poor with values of −1.0 ≲ [Fe/H]phot ≲ −0.7 with an 〈[Fe/H]phot〉 ∼ −0.9. We find consistent properties for the Eastern Extent, Stream B and one of the substructures in Stream C, Stream Cr, plausibly linking these features. Stream Cp and its associated globular cluster, EC4, have distinctly different properties indicative of a separate structure. When we compare the properties of the Eastern Extent to those of the Giant Stellar Stream, we find them to be consistent, albeit slightly more metal-poor, such that the Eastern Extent could plausibly comprise stars stripped from the progenitor of the Giant Stellar Stream.
      PubDate: Thu, 08 Apr 2021 00:00:00 GMT
      DOI: 10.1093/mnras/stab957
      Issue No: Vol. 504, No. 2 (2021)
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