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  Subjects -> METEOROLOGY (Total: 106 journals)
Showing 1 - 36 of 36 Journals sorted by number of followers
Journal of Atmospheric and Solar-Terrestrial Physics     Hybrid Journal   (Followers: 156)
Nature Climate Change     Full-text available via subscription   (Followers: 150)
Journal of the Atmospheric Sciences     Hybrid Journal   (Followers: 80)
Atmospheric Research     Hybrid Journal   (Followers: 73)
Atmospheric Environment     Hybrid Journal   (Followers: 72)
Climatic Change     Open Access   (Followers: 71)
Bulletin of the American Meteorological Society     Open Access   (Followers: 63)
Advances in Climate Change Research     Open Access   (Followers: 60)
Journal of Climate     Hybrid Journal   (Followers: 56)
Climate Policy     Hybrid Journal   (Followers: 53)
Climate Change Economics     Hybrid Journal   (Followers: 50)
Climate Dynamics     Hybrid Journal   (Followers: 45)
Advances in Atmospheric Sciences     Hybrid Journal   (Followers: 44)
Weather and Forecasting     Hybrid Journal   (Followers: 43)
Atmospheric Chemistry and Physics (ACP)     Open Access   (Followers: 43)
American Journal of Climate Change     Open Access   (Followers: 42)
Journal of Applied Meteorology and Climatology     Hybrid Journal   (Followers: 41)
Nature Reports Climate Change     Full-text available via subscription   (Followers: 40)
Atmospheric Science Letters     Open Access   (Followers: 40)
Journal of Hydrology and Meteorology     Open Access   (Followers: 39)
Atmosphere     Open Access   (Followers: 33)
Journal of Atmospheric and Oceanic Technology     Hybrid Journal   (Followers: 33)
International Journal of Climate Change Strategies and Management     Hybrid Journal   (Followers: 32)
The Quarterly Journal of the Royal Meteorological Society     Hybrid Journal   (Followers: 32)
Boundary-Layer Meteorology     Hybrid Journal   (Followers: 31)
Journal of Space Weather and Space Climate     Open Access   (Followers: 30)
Monthly Weather Review     Hybrid Journal   (Followers: 30)
Meteorology and Atmospheric Physics     Hybrid Journal   (Followers: 29)
International Journal of Climatology     Hybrid Journal   (Followers: 28)
Climate Change Responses     Open Access   (Followers: 27)
Space Weather     Full-text available via subscription   (Followers: 27)
Advances in Meteorology     Open Access   (Followers: 27)
Climate Resilience and Sustainability     Open Access   (Followers: 26)
Energy & Environment     Hybrid Journal   (Followers: 26)
Journal of Climate Change     Full-text available via subscription   (Followers: 25)
International Journal of Atmospheric Sciences     Open Access   (Followers: 25)
International Journal of Environment and Climate Change     Open Access   (Followers: 24)
Environmental Dynamics and Global Climate Change     Open Access   (Followers: 24)
Journal of Atmospheric Chemistry     Hybrid Journal   (Followers: 23)
Current Climate Change Reports     Hybrid Journal   (Followers: 22)
Tellus A     Open Access   (Followers: 21)
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 21)
Global Meteorology     Open Access   (Followers: 20)
Tellus B     Open Access   (Followers: 20)
Journal of Economic Literature     Hybrid Journal   (Followers: 20)
Dynamics of Atmospheres and Oceans     Hybrid Journal   (Followers: 19)
Journal of Meteorology and Climate Science     Full-text available via subscription   (Followers: 19)
Weather and Climate Extremes     Open Access   (Followers: 18)
Weatherwise     Hybrid Journal   (Followers: 18)
Atmosphere-Ocean     Full-text available via subscription   (Followers: 16)
Economics of Disasters and Climate Change     Hybrid Journal   (Followers: 16)
Atmospheric Chemistry and Physics Discussions (ACPD)     Open Access   (Followers: 15)
Theoretical and Applied Climatology     Hybrid Journal   (Followers: 14)
Monthly Notices of the Royal Astronomical Society     Hybrid Journal   (Followers: 13)
Atmospheric and Oceanic Science Letters     Open Access   (Followers: 13)
Climate Risk Management     Open Access   (Followers: 12)
Advances in Statistical Climatology, Meteorology and Oceanography     Open Access   (Followers: 12)
Journal of Hydrometeorology     Hybrid Journal   (Followers: 10)
The Cryosphere (TC)     Open Access   (Followers: 8)
Climate Research     Hybrid Journal   (Followers: 8)
Climate and Energy     Full-text available via subscription   (Followers: 8)
Climate     Open Access   (Followers: 7)
Journal of the Meteorological Society of Japan     Partially Free   (Followers: 7)
Aeolian Research     Hybrid Journal   (Followers: 7)
Climate of the Past (CP)     Open Access   (Followers: 7)
Climate Law     Hybrid Journal   (Followers: 6)
Journal of Climate Change and Health     Open Access   (Followers: 6)
npj Climate and Atmospheric Science     Open Access   (Followers: 6)
Dynamics and Statistics of the Climate System     Open Access   (Followers: 6)
Carbon Balance and Management     Open Access   (Followers: 6)
Open Journal of Modern Hydrology     Open Access   (Followers: 5)
Bulletin of Atmospheric Science and Technology     Hybrid Journal   (Followers: 5)
Open Atmospheric Science Journal     Open Access   (Followers: 5)
Urban Climate     Hybrid Journal   (Followers: 5)
Climate Services     Open Access   (Followers: 4)
Journal of Climatology     Open Access   (Followers: 4)
Journal of Integrative Environmental Sciences     Hybrid Journal   (Followers: 4)
Frontiers in Climate     Open Access   (Followers: 4)
Russian Meteorology and Hydrology     Hybrid Journal   (Followers: 4)
Meteorologische Zeitschrift     Full-text available via subscription   (Followers: 4)
Journal of Weather Modification     Full-text available via subscription   (Followers: 4)
Meteorological Applications     Open Access   (Followers: 4)
Acta Meteorologica Sinica     Hybrid Journal   (Followers: 4)
Atmospheric Environment : X     Open Access   (Followers: 3)
Oxford Open Climate Change     Open Access   (Followers: 3)
Environmental and Climate Technologies     Open Access   (Followers: 3)
International Journal of Biometeorology     Hybrid Journal   (Followers: 3)
International Journal of Image and Data Fusion     Hybrid Journal   (Followers: 3)
Atmósfera     Open Access   (Followers: 2)
GeoHazards     Open Access   (Followers: 2)
Journal of Meteorological Research     Full-text available via subscription   (Followers: 2)
Mediterranean Marine Science     Open Access   (Followers: 2)
Meteorologica     Open Access   (Followers: 2)
气候与环境研究     Full-text available via subscription   (Followers: 2)
Weather and Climate Dynamics     Open Access   (Followers: 1)
Modeling Earth Systems and Environment     Hybrid Journal   (Followers: 1)
Michigan Journal of Sustainability     Open Access   (Followers: 1)
Earth Perspectives - Transdisciplinarity Enabled     Open Access   (Followers: 1)
Tropical Cyclone Research and Review     Open Access   (Followers: 1)
Ciencia, Ambiente y Clima     Open Access   (Followers: 1)
Climate of the Past Discussions (CPD)     Open Access   (Followers: 1)
Nīvār     Open Access   (Followers: 1)
Meteorological Monographs     Hybrid Journal   (Followers: 1)
Studia Geophysica et Geodaetica     Hybrid Journal   (Followers: 1)
Revista Iberoamericana de Bioeconomía y Cambio Climático     Open Access   (Followers: 1)
Journal of Agricultural Meteorology     Open Access  
Mètode Science Studies Journal : Annual Review     Open Access  

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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  [419 journals]
  • Gap opening by planets in discs with magnetized winds

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      Pages: 3113 - 3125
      Abstract: ABSTRACTPlanets open deep gaps in protoplanetary discs when their mass exceeds a gap opening mass, Mgap. We use one- and two-dimensional simulations to study planet gap opening in discs with angular momentum transport powered by MHD disc winds. We parametrize the efficiency of the MHD disc wind angular momentum transport through a dimensionless parameter αdw, which is an analogue to the turbulent viscosity αv. We find that magnetized winds are much less efficient in counteracting planet tidal torques than turbulence is. For discs with astrophysically realistic values of αdw, Mgap is always determined by the residual disc turbulence, and is a factor of a few to ten smaller than usually obtained for viscous discs. We introduce a gap opening criterion applicable for any values of αv and αdw that may be useful for planet formation population synthesis. We show that in discs powered by magnetized winds growing planets detach from the disc at planet masses below $\sim 0.1{\, {\rm M}_{\rm J}}$ inside 10 au. This promotes formation of super-Earth planets rather than gas giants in this region, in particular precluding formation of hot jupiters in situ. On larger scales, ALMA gap opening planet candidates may be less massive than currently believed. Future high-resolution observations with instruments such as the extended ALMA, ngVLA, and SKA are likely to show abundant narrow annular features at R < 10 au due to ubiquitous super-Earth planets.
      PubDate: Tue, 28 Jun 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1774
      Issue No: Vol. 515, No. 3 (2022)
       
  • The ALMA REBELS Survey: dust continuum detections at z &gt; 6.5

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      Pages: 3126 - 3143
      Abstract: ABSTRACTWe report 18 dust continuum detections (≥3.3σ) at ∼88 and 158 $\mu{\rm m}$ out of 49 ultraviolet (UV)-bright galaxies (MUV < −21.3 mag) at $z$ > 6.5, observed by the Cycle-7 Atacama Large Millimeter/submillimeter Array (ALMA) Large Program, Reionization-Era Bright Emission Line Survey (REBELS) and its pilot programs. This has more than tripled the number of dust continuum detections known at $z$ > 6.5. Out of these 18 detections, 12 are reported for the first time as part of REBELS. In addition, 15 of the dust continuum detected galaxies also show a [C ii]$_{\rm 158\,{\rm \mu m}}$ emission line, providing us with accurate redshifts. We anticipate more line emission detections from six targets (including three continuum detected targets) where observations are still ongoing. We estimate that all of the sources have an infrared (IR) luminosity (LIR) in a range of $3\!-\!8 \times 10^{11}\, {\rm L_\odot }$, except for one with $L_{\rm IR} = 1.5^{+0.8}_{-0.5} \times 10^{12}\, \, {\rm L_{\odot }}$. Their fraction of obscured star formation is significant at ${\gtrsim} 50{{\ \rm per\ cent}}$, despite being UV-selected galaxies. Some of the dust continuum detected galaxies show spatial offsets (∼0.5–1.5 arcsec) between the rest-UV and far-IR emission peaks. These separations could imply spatially decoupled phases of obscured and unobscured star formation, but a higher spatial resolution observation is required to confirm this. REBELS offers the best available statistical constraints on obscured star formation in UV-luminous galaxies at $z$ > 6.5.
      PubDate: Tue, 28 Jun 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1779
      Issue No: Vol. 515, No. 3 (2022)
       
  • GRMHD simulations of accreting neutron stars with non-dipole fields

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      Pages: 3144 - 3161
      Abstract: ABSTRACTNASA’s NICER telescope has recently provided evidence for non-dipolar magnetic field structures in rotation-powered millisecond pulsars. These stars are assumed to have gone through a prolonged accretion spin-up phase, begging the question of what accretion flows on to stars with complex magnetic fields would look like. We present results from a suite of general relativistic magnetohydrodynamic simulations of accreting neutron stars for dipole, quadrupole, and quadrudipolar stellar field geometries. This is a first step towards simulating realistic hotspot shapes in a general relativistic framework to understand hotspot variability in accreting millisecond pulsars. We find that the location and size of the accretion columns resulting in hotspots changes significantly depending on initial stellar field strength and geometry. We also find that the strongest contributions to the stellar torque are from disc-connected field lines and the pulsar wind, leading to spin-down in almost the entire parameter regime explored here. We further analyse angular momentum transport in the accretion disc due to large-scale magnetic stresses, turbulent stresses, and wind and compressible effects which we identify with convective motions. The disc collimates the initial open stellar flux forming jets. For dipoles, the disc–magnetosphere interaction can either enhance or reduce jet power compared to the isolated case. However for quadrupoles, the disc always leads to an enhanced net open flux making the jet power comparable to the dipolar case. We discuss our results in the context of observed neutron star jets and provide a viable mechanism to explain radio power both in the low- and high-magnetic field case.
      PubDate: Fri, 01 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1817
      Issue No: Vol. 515, No. 3 (2022)
       
  • Galaxy cluster photons alter the ionization state of the nearby
           warm–hot intergalactic medium

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      Pages: 3162 - 3173
      Abstract: ABSTRACTThe physical properties of the faint and extremely tenuous plasma in the far outskirts of galaxy clusters, the circumgalactic media of normal galaxies, and filaments of the cosmic web remain one of the biggest unknowns in our story of large-scale structure evolution. Modelling the spectral features due to emission and absorption from this very diffuse plasma poses a challenge, as both collisional and photoionization processes must be accounted for. In this paper, we study the ionization by photons emitted by the intracluster medium in addition to the photoionization by the cosmic ultraviolet/X-ray background on gas in the vicinity of galaxy clusters. For near-massive clusters such as A2029, the ionization parameter can no longer describe the ionization balance uniquely. The ionization fractions (in particular of C iv, C v, C vi, N vii, O vi, O vii, O viii, Ne viii, Ne ix, and Fe xvii) obtained by taking into account the photoionization by the cosmic background are either an upper or lower limit to the ionization fraction calculated as a function of distance from the emission from the cluster. Using a toy model of a cosmic web filament, we predict how the cluster illumination changes the column densities for two different orientations of the line of sight. For lines of sight passing close to the cluster outskirts, O vi can be suppressed by a factor of up to 4.5, O vii by a factor of 2.2, C v by a factor of 3, and Ne viii can be boosted by a factor of 2, for low-density gas.
      PubDate: Tue, 05 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1854
      Issue No: Vol. 515, No. 3 (2022)
       
  • Hard X-Ray broadband spectroscopy of Mrk 876: characterizing its
           spectrum

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      Pages: 3174 - 3183
      Abstract: ABSTRACTEver since the launch of the NuSTAR mission, the hard X-ray range is being covered to an unprecedented sensitivity. This range encodes the reflection features arising from active galactic nuclei (AGNs). Especially, the reflection of the primary radiation off the accretion disc carries the features of the manifestation of General Relativity described by the Kerr metric due to rotating supermassive black holes (SMBHs). We show the results of the broadband analyses of Mrk 876. The spectra exhibit the signature of a Compton hump at energies above 10 keV and a broadened and skewed excess at energies ∼6 keV. We establish this spectral excess to be statistically significant at 99.71 per cent (∼3σ) that is the post-trail probability through Monte Carlo simulations. Based on the spectral fit results and the significance of spectral features, the relativistic reflection model is favoured over the distant reflection scenario. The excess at ∼6 keV has a complex shape that we try to recover along with the Compton hump through a self-consistent X-ray reflection model. This allows inferring an upper limit to the black hole spin of a ≤ 0.85, while the inclination angle of the accretion disc results in i = 32.84$^{\circ }{}^{+12.22}_{-8.99}$, which is in agreement within the errors with a previous independent measurement (i = 15.4$^{\circ }{}^{+12.1}_{-6.8}$). While most spin measurements are biased towards high spin values, the black hole mass of Mrk 876 (2.4$\times 10^{8}\, \mbox{M}_\odot \le$ MSMBH $\le ~1.3 \times 10^{9}\, \mbox{M}_\odot$) lies in a range where moderately spinning SMBHs are expected. Moreover, the analyses of 12 Chandra observations reveal for the first time X-ray variability of Mrk 876 with an amplitude of 40 per cent.
      PubDate: Mon, 25 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1890
      Issue No: Vol. 515, No. 3 (2022)
       
  • Integrated mass-loss of evolved stars in M4 using asteroseismology

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      Pages: 3184 - 3198
      Abstract: ABSTRACTMass-loss remains a major uncertainty in stellar modelling. In low-mass stars, mass-loss is most significant on the red giant branch (RGB), and will impact the star’s evolutionary path and final stellar remnant. Directly measuring the mass difference of stars in various phases of evolution represents one of the best ways to quantify integrated mass-loss. Globular clusters (GCs) are ideal objects for this. M4 is currently the only GC for which asteroseismic data exist for stars in multiple phases of evolution. Using K2 photometry, we report asteroseismic masses for 75 red giants in M4, the largest seismic sample in a GC to date. We find an integrated RGB mass-loss of $\Delta \overline{M} = 0.17 \pm 0.01 ~\mathrm{M}_{\odot }$, equivalent to a Reimers’ mass-loss coefficient of ηR = 0.39. Our results for initial mass, horizontal branch mass, ηR, and integrated RGB mass-loss show remarkable agreement with previous studies, but with higher precision using asteroseismology. We also report the first detections of solar-like oscillations in early asymptotic giant branch (EAGB) stars in GCs. We find an average mass of $\overline{M}_{\text{EAGB}}=0.54 \pm 0.01 ~\mathrm{M}_{\odot }$, significantly lower than predicted by models. This suggests larger-than-expected mass-loss on the horizontal branch. Alternatively, it could indicate unknown systematics in the scaling relations for the EAGB. We discover a tentative mass bimodality in the RGB sample, possibly due to the multiple populations. In our red horizontal branch sample, we find a mass distribution consistent with a single value. We emphasize the importance of seismic studies of GCs since they could potentially resolve major uncertainties in stellar theory.
      PubDate: Mon, 25 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1918
      Issue No: Vol. 515, No. 3 (2022)
       
  • Compact groups in GDM cosmological simulations

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      Pages: 3199 - 3211
      Abstract: ABSTRACTIn this work, we study some properties of the Hickson Compact Groups (HCGs) using N-body simulations for the Generalized Dark Matter (GDM) model, described by three free functions, the sound speed, the viscosity, and the equation of state. We consider three GDM models associated with different values of the free functions to neglect collisional effects. We constructed the initial seeds of our simulations according to the matter power spectrum of GDM linear perturbations, which hold a cut-off at small scales, and explored their effects on the non-linear structure formation at small and intermediate scales. We generated mock catalogues of galaxies for different models and classified HCGs by implementing an algorithm that adapts the original selection method for mock catalogues. Once the HCGs samples were classified, we analysed their properties and compared them between models. We found that a larger amount of HCGs are counted in GDM simulations in comparison to CDM counts. This difference suggests that HCGs can proliferate within GDM despite the suppressed substructure, which indicates a possible modification in the HCG formation process within models where DM is not perfectly like CDM. Additionally, we identified different mechanisms of clustering, for models with a large amount of galaxy-haloes self-agglomerate because of their abundance while models with fewer galaxy-haloes need massive haloes acting as a dominant potential well. Finally, by comparing distributions of different observables of simulated HCGs against observations, we found a good agreement in the intrinsic properties. However, a discrepancy in the velocity dispersion remains unsolved.
      PubDate: Sun, 31 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1925
      Issue No: Vol. 515, No. 3 (2022)
       
  • A search for transit timing variations in the HATS-18 planetary system

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      Pages: 3212 - 3223
      Abstract: ABSTRACTHATS-18 b is a transiting planet with a large mass and a short orbital period, and is one of the best candidates for the detection of orbital decay induced by tidal effects. We present extensive photometry of HATS-18 from which we measure 27 times of mid-transit. Two further transit times were measured from data from the Transiting Exoplanet Survey Satellite (TESS) and three more taken from the literature. The transit timings were fitted with linear and quadratic ephemerides and an upper limit on orbital decay was determined. This corresponds to a lower limit on the modified stellar tidal quality factor of $Q_\star ^{\, \prime } \gt 10^{5.11 \pm 0.04}$. This is at the cusp of constraining the presence of enhanced tidal dissipation due to internal gravity waves. We also refine the measured physical properties of the HATS-18 system, place upper limits on the masses of third bodies, and compare the relative performance of TESS and the 1.54 m Danish Telescope in measuring transit times for this system.
      PubDate: Tue, 12 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1931
      Issue No: Vol. 515, No. 3 (2022)
       
  • Paving the way forEuclid and JWST via probabilistic selection of
           high-redshift quasars

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      Pages: 3224 - 3248
      Abstract: ABSTRACTWe introduce a probabilistic approach to select 6 ≤ $z$ ≤ 8 quasar candidates for spectroscopic follow-up, which is based on density estimation in the high-dimensional space inhabited by the optical and near-infrared photometry. Densities are modelled as Gaussian mixtures with principled accounting of errors using the extreme deconvolution (XD) technique, generalizing an approach successfully used to select lower redshift ($z$ ≤ 3) quasars. We train the probability density of contaminants on 1902 071 7-d flux measurements from the 1076 deg2 overlapping area from the Dark Energy Camera Legacy Survey (DECaLS) ($z$), VIKING (YJHKs), and unWISE (W1W2) imaging surveys, after requiring they dropout of DECaLS g and r, whereas the distribution of high-$z$ quasars are trained on synthetic model photometry. Extensive simulations based on these density distributions and current estimates of the quasar luminosity function indicate that this method achieves a completeness of $\ge 56{{\ \rm per\ cent}}$ and an efficiency of $\ge 5{{\ \rm per\ cent}}$ for selecting quasars at 6 < $z$ < 8 with JAB < 21.5. Among the classified sources are 8 known 6 < $z$ < 7 quasars, of which 2/8 are selected suggesting a completeness $\simeq 25{{\ \rm per\ cent}}$, whereas classifying the 6 known (JAB < 21.5) quasars at $z$ > 7 from the entire sky, we select 5/6 or a completeness of $\simeq 80{{\ \rm per\ cent}}$. The failure to select the majority of 6 < $z$ < 7 quasars arises because our quasar density model is based on an empirical quasar spectral energy distribution model that underestimates the scatter in the distribution of fluxes. This new approach to quasar selection paves the way for efficient spectroscopic follow-up of Euclid quasar candidates with ground-based telescopes and James Webb Space Telescope.
      PubDate: Sat, 23 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1944
      Issue No: Vol. 515, No. 3 (2022)
       
  • A stochastic model to reproduce the star formation history of individual
           galaxies in hydrodynamic simulations

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      Pages: 3249 - 3269
      Abstract: ABSTRACTThe star formation history (SFH) of galaxies is critical for understanding galaxy evolution. Hydrodynamical simulations enable us to precisely reconstruct the SFH of galaxies and establish a link to the underlying physical processes. In this work, we present a model to describe individual galaxies’ SFHs from three simulations: TheThreeHundred, Illustris-1, and TNG100-1. This model divides the galaxy SFH into two distinct components: the ‘main sequence’ and the ‘variation’. The ‘main sequence’ part is generated by tracing the history of the SFR − M* main sequence of galaxies across time. The ‘variation’ part consists of the scatter around the main sequence, which is reproduced by fractional Brownian motions. We find that: (1) the evolution of the main sequence varies between simulations; (2) fractional Brownian motions can reproduce many features of SFHs; however, discrepancies still exist; and (3) the variations and mass-loss rate are crucial for reconstructing the SFHs of the simulations. This model provides a fair description of the SFHs in simulations. On the other hand, by correlating the fractional Brownian motion model to simulation data, we provide a ’standard’ against which to compare simulations.
      PubDate: Wed, 13 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1956
      Issue No: Vol. 515, No. 3 (2022)
       
  • A multiwavelength study of star formation in nearby galaxies: evidence for
           inside-out growth of the stellar disc

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      Pages: 3270 - 3298
      Abstract: ABSTRACTGlobal, radial, and local photometric measurements of several nearby low-mass galaxies are presented. Multiwavelength observations are used to trace the distributions of old and young stars, with the help of far-ultraviolet (FUV) to mid-infrared spectral energy distributions to derive star formation histories (SFHs). In addition to the surface brightness profiles, catalogues of UV-selected sources are created to better understand regions of galaxies with recent star formation. The clustering of these UV sources are studied in the dwarf irregular UGC 08188 (IC 4182) using a two-point correlation function. We find that the reddest of these UV sources are not clustered on any scale, but the bluer sources are clustered on scales approximately less than 1 kpc. We also find a possible negative radial gradient in the SFH parameter that marks the beginning of the younger stellar population’s formation (tburst) when analysing the entire sample of 3165 UV sources found across a total of 34 galaxies, giving quantitative evidence for the inside-out growth of galactic discs – a natural consequence of galaxy evolution in a Λ cold dark matter universe.
      PubDate: Thu, 21 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1974
      Issue No: Vol. 515, No. 3 (2022)
       
  • Astrophysical gravitational-wave echoes from galactic nuclei

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      Pages: 3299 - 3318
      Abstract: ABSTRACTGalactic nuclei (GNs) are dense stellar environments abundant in gravitational-wave (GW) sources for the Laser Interferometer Gravitational-Wave Observatory (LIGO), Virgo, and Kamioka Gravitational Wave Detector (KAGRA). The GWs may be generated by stellar-mass black hole (BH) or neutron star mergers following gravitational bremsstrahlung, dynamical scattering encounters, Kozai–Lidov-type oscillations driven by the central supermassive black hole (SMBH), or gas-assisted mergers if present. In this paper, we examine a smoking gun signature to identify sources in GNs: the GWs scattered by the central SMBH. This produces a secondary signal, an astrophysical GW echo, which has a very similar time–frequency evolution as the primary signal but arrives after a time delay. We determine the amplitude and time-delay distribution of the GW echo as a function of source distance from the SMBH. Between ${\sim} 10{{\ \rm per\ cent}}\hbox{ and }90{{\ \rm per\ cent}}$ of the detectable echoes arrive within ${\sim} (1\hbox{--}100)M_6\, \mathrm{s}$ after the primary GW for sources between 10 and 104 Schwarzschild radius, where $M_6=M_{{\rm SMBH},z}/(10^6\, \mathrm{M}_{\odot })$, and MSMBH, z is the observer-frame SMBH mass. The echo arrival times are systematically longer for high signal-to-noise ratio (SNR) primary GWs, where the GW echo rays are scattered at large deflection angles. In particular, ${\sim} 10{{\ \rm per\ cent}}\hbox{--}90{{\ \rm per\ cent}}$ of the distribution is shifted to ${\sim} (5\hbox{--}1800)M_6\, \mathrm{s}$ for sources, where the lower limit of echo detection is 0.02 of the primary signal amplitude. We find that ${\sim} 5{{\ \rm per\ cent}}\hbox{--}30{{\ \rm per\ cent}}$ (${\sim} 1{{\ \rm per\ cent}}\hbox{--}7{{\ \rm per\ cent}}$) of GW sources have an echo amplitude larger than 0.2–0.05 times the amplitude of the primary signal if the source distance from the SMBH is 50 (200) Schwarzschild radius. Non-detections can rule out that a GW source is near an SMBH.
      PubDate: Fri, 22 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1985
      Issue No: Vol. 515, No. 3 (2022)
       
  • The kinematics and ionization structure of the extended emission-line
           region of QSO E1821+643

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      Pages: 3319 - 3335
      Abstract: ABSTRACTThe most luminous quasars are created by major, gas-rich mergers and E1821+643, an optically luminous quasar situated at the centre of a cool-core cluster, appears to be in the late stages of the post-merger blowout phase. This quasar is also identified as a gravitational recoil candidate, in which the supermassive black hole (SMBH) has received a recoil kick due to anisotropic emission of gravitational waves during the coalescence of a progenitor SMBH binary. We analyse long-slit spectra of the extended, ionized gas surrounding E1821+643 to study its kinematics and ionization. We have identified three kinematically distinct components, which we associate, respectively, with a wide-angle polar wind from the nucleus, kinematically undisturbed gas, and a redshifted arc-like structure of gas, at a distance of 3–4 arcsec (13–18 kpc) from the nucleus. The latter component coincides with the northern and eastern extremities of an arc of [O iii] emission seen in HST images. This feature could trace a tidal tail originating from a merger with a gas-rich galaxy to the south-east of the nucleus, whose presence has been inferred by Aravena et al. from the detection of CO emission. Alternatively, the arc could be the remnant of a shell of gas swept up by a powerful quasar wind. The emission-line ratios of the extended gas are consistent with photoionization by the quasar, but a contribution from radiative shocks cannot be excluded.
      PubDate: Sat, 23 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1995
      Issue No: Vol. 515, No. 3 (2022)
       
  • Hidden cooling flows in clusters of galaxies

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      Pages: 3336 - 3345
      Abstract: ABSTRACTThe radiative cooling time of the hot gas at the centres of cool cores in clusters of galaxies drops down to 10 Myr and below. The observed mass cooling rate of such gas is very low, suggesting that active galactic nucleus feedback is very tightly balanced or that the soft X-ray emission from cooling is somehow hidden from view. We use an intrinsic absorption model in which the cooling and coolest gas are closely interleaved to search for hidden cooling flows in the Centaurus, Perseus, and A1835 clusters of galaxies. We find hidden mass cooling rates of between 10 and $500\,{{\rm M_{\odot }}\,{\rm yr}^{-1}}$ as the cluster mass increases, with the absorbed emission emerging in the far-infrared (FIR) band. Good agreement is found between the hidden cooling rate and observed FIR luminosity in the Centaurus Cluster. The limits on the other two clusters allow for considerable hidden cooling. The implied total mass of cooled gas is much larger than the observed molecular masses. We discuss its fate including possible further cooling and collapse into undetected very cold clouds, low-mass stars, and substellar objects.
      PubDate: Sat, 23 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac2003
      Issue No: Vol. 515, No. 3 (2022)
       
  • Linear change and minutes variability of solar wind velocity revealed by
           FAST

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      Pages: 3346 - 3351
      Abstract: ABSTRACTObservation of Interplanetary Scintillation (IPS) provides an important and effective way to study the solar wind and the space weather. A series of IPS observations were conducted by the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The extraordinary sensitivity and the wide frequency coverage make FAST an ideal platform for IPS studies. In this paper, we present some first scientific results from FAST observations of IPS with the L-band receiver. Based on the solar wind velocity fitting values of FAST observations on 2020 September 26–28, we found that the velocity decreases with increasing frequency linearly, which has not yet been reported in literature. And we have also detected a variation of solar wind velocity on a time-scale of 3–5 min, which imply the slow change of the background solar wind, a co-existence of high- and low-speed streams, or a reflect of the quasi-periodic electron-density fluctuations.
      PubDate: Fri, 22 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac2059
      Issue No: Vol. 515, No. 3 (2022)
       
  • Revealing the dust grain polarization properties as a function of
           extinction and distance towards NGC 1893

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      Pages: 3352 - 3369
      Abstract: ABSTRACTDust polarization observations at optical wavelengths help us to understand the dust grain properties and trace the plane-of-the-sky component of the magnetic field. In this study, we make use of the I-band polarization data acquired from AIMPOL along with the distances (d) and extinction (AV) data to study the variation of polarization fraction (P) as a function of AV and d towards the star-forming region, NGC 1893. We employ a broken power-law fit and Bayesian analysis on extinction (AV) versus polarization efficiency (P/AV) and distance (d) versus rate of polarization (P/d). We find that P/AV shows a break at an extinction of ∼0.9 mag, whereas P/d exhibits a break at a distance of ∼1.5 kpc. Based on these, we categorize the dust towards NGC 1893 into two populations: (i) foreground dust confined to AV < ∼1 mag and distance up to ∼2 kpc and (ii) Perseus spiral arm dust towards NGC 1893 characterized with AV > ∼1 mag and distance beyond ∼2 kpc. Foreground dust exhibits higher polarization efficiency but a lower polarization rate, whereas Perseus dust shows a lower polarization efficiency but a slightly higher polarization rate. Hence, we suggest that while polarization efficiency reveals the dust grain alignment, the rate of polarization infers about the distribution of dust grains towards NGC 1893. Further, we also shed a light on the spatial variation of intrinsic polarization and magnetic field orientation, and other parameters within the intracluster medium of NGC 1893.
      PubDate: Fri, 05 Aug 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1927
      Issue No: Vol. 515, No. 3 (2022)
       
  • A Roche lobe-filling hot subdwarf and white dwarf binary: possible
           detection of an ejected common envelope

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      Pages: 3370 - 3382
      Abstract: ABSTRACTBinaries consisting of a hot subdwarf star and an accreting white dwarf (WD) are sources of gravitational wave radiation at low frequencies and possible progenitors of Type Ia supernovae if the WD mass is large enough. Here, we report the discovery of the third binary known of this kind: It consists of a hot subdwarf O (sdO) star and a WD with an orbital period of 3.495 h and an orbital shrinkage of 0.1 s in 6 yr. The sdO star overfills its Roche lobe and likely transfers mass to the WD via an accretion disc. From spectroscopy, we obtain an effective temperature of $T_{\mathrm{eff}}=54\, 240\pm 1840$ K and a surface gravity of log g = 4.841 ± 0.108 for the sdO star. From the light curve analysis, we obtain an sdO mass of MsdO = 0.55 M⊙ and a mass ratio of q = MWD/MsdO = 0.738 ± 0.001. Also, we estimate that the disc has a radius of $\sim\!0.41\ \mathrm{R}_\odot$ and a thickness of $\sim\!0.18\ \mathrm{R}_\odot$. The origin of this binary is probably a common envelope ejection channel, where the progenitor of the sdO star is either a red giant branch star or, more likely, an early asymptotic giant branch star; the sdO star will subsequently evolve into a WD and merge with its WD companion, likely resulting in an R Coronae Borealis (R CrB) star. The outstanding feature in the spectrum of this object is strong Ca H&K lines, which are blueshifted by ∼200 km s−1 and likely originate from the recently ejected common envelope, and we estimated that the remnant common envelope (CE) material in the binary system has a density $\sim\!6\times 10^{-10}\ {\rm g\, cm}^{-3}$.
      PubDate: Thu, 07 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1768
      Issue No: Vol. 515, No. 3 (2022)
       
  • Why are we still using 3D masses for cluster cosmology'

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      Pages: 3383 - 3405
      Abstract: ABSTRACTThe abundance of clusters of galaxies is highly sensitive to the late-time evolution of the matter distribution, since clusters form at the highest density peaks. However, the 3D cluster mass cannot be inferred without deprojecting the observations, introducing model-dependent biases and uncertainties due to the mismatch between the assumed and the true cluster density profile and the neglected matter along the sightline. Since projected aperture masses can be measured directly in simulations and observationally through weak lensing, we argue that they are better suited for cluster cosmology. Using the Mira–Titan suite of gravity-only simulations, we show that aperture masses correlate strongly with 3D halo masses, albeit with large intrinsic scatter due to the varying matter distribution along the sightline. Nonetheless, aperture masses can be measured ≈2–3 times more precisely from observations, since they do not require assumptions about the density profile and are only affected by the shape noise in the weak lensing measurements. We emulate the cosmology dependence of the aperture mass function directly with a Gaussian process. Comparing the cosmology sensitivity of the aperture mass function and the 3D halo mass function for a fixed survey solid angle and redshift interval, we find the aperture mass sensitivity is higher for Ωm and $w_a$, similar for σ8, ns, and $w_0$, and slightly lower for h. With a carefully calibrated aperture mass function emulator, cluster cosmology analyses can use cluster aperture masses directly, reducing the sensitivity to model-dependent mass calibration biases and uncertainties.
      PubDate: Fri, 17 Jun 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1687
      Issue No: Vol. 515, No. 3 (2022)
       
  • The observability of galaxy merger signatures in nearby gas-rich spirals

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      Pages: 3406 - 3419
      Abstract: ABSTRACTGalaxy mergers are crucial to understanding galaxy evolution, therefore we must determine their observational signatures to select them from large IFU galaxy samples such as MUSE and SAMI. We employ 24 high-resolution idealized hydrodynamical galaxy merger simulations based on the ‘Feedback In Realistic Environment’ (FIRE-2) model to determine the observability of mergers to various configurations and stages using synthetic images and velocity maps. Our mergers cover a range of orbital configurations at fixed 1:2.5 stellar mass ratio for two gas rich spirals at low redshift. Morphological and kinematic asymmetries are computed for synthetic images and velocity maps spanning each interaction. We divide the interaction sequence into three: (1) the pair phase; (2) the merging phase; and (3) the post-coalescence phase. We correctly identify mergers between first pericentre passage and 500 Myr after coalescence using kinematic asymmetry with 66 per cent completeness, depending upon merger phase and the field of view of the observation. We detect fewer mergers in the pair phase (40 per cent) and many more in the merging and post-coalescence phases (97 per cent). We find that merger detectability decreases with field of view, except in retrograde mergers, where centrally concentrated asymmetric kinematic features enhances their detectability. Using a cut-off derived from a combination of photometric and kinematic asymmetry, we increase these detections to 89 per cent overall, 79 per cent in pairs, and close to 100 per cent in the merging and post-coalescent phases. By using this combined asymmetry cut-off we mitigate some of the effects caused by smaller fields of view subtended by massively multiplexed integral field spectroscopy programmes.
      PubDate: Wed, 29 Jun 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1715
      Issue No: Vol. 515, No. 3 (2022)
       
  • Cometary dust analogues for physics experiments

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      Pages: 3420 - 3438
      Abstract: ABSTRACTThe CoPhyLab (Cometary Physics Laboratory) project is designed to study the physics of comets through a series of earth-based experiments. For these experiments, a dust analogue was created with physical properties comparable to those of the non-volatile dust found on comets. This ‘CoPhyLab dust’ is planned to be mixed with water and CO2 ice and placed under cometary conditions in vacuum chambers to study the physical processes taking place on the nuclei of comets. In order to develop this dust analogue, we mixed two components representative for the non-volatile materials present in cometary nuclei. We chose silica dust as a representative for the mineral phase and charcoal for the organic phase, which also acts as a darkening agent. In this paper, we provide an overview of known cometary analogues before presenting measurements of eight physical properties of different mixtures of the two materials and a comparison of these measurements with known cometary values. The physical properties of interest are particle size, density, gas permeability, spectrophotometry, and mechanical, thermal, and electrical properties. We found that the analogue dust that matches the highest number of physical properties of cometary materials consists of a mixture of either 60 per cent/40 per cent or 70 per cent/30 per cent of silica dust/charcoal by mass. These best-fit dust analogue will be used in future CoPhyLab experiments.
      PubDate: Sat, 25 Jun 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1734
      Issue No: Vol. 515, No. 3 (2022)
       
  • Asteroseismology of RR Lyrae stars with non-radial modes

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      Pages: 3439 - 3452
      Abstract: ABSTRACTThe additional signals observed in the frequency spectra of the first-overtone RR Lyrae stars, which form a period ratio around 0.61 with the period of the first overtone, are a common phenomenon for RRc and RRd stars, as well as for first-overtone classical Cepheids. The recently proposed model explains these signals as harmonics of non-radial modes of degrees 8 or 9 in the case of RR Lyrae stars and 7, 8, or 9 in the case of classical Cepheids. We selected at least triple-mode RR Lyrae stars pulsating in radial and non-radial modes for asteroseismic modelling. We assume the identification of the non-radial modes as predicted by the model. We calculated a dense grid of models for RR Lyrae stars using envelope pulsation code. By matching first-overtone period and period ratios, we obtained physical parameters for the selected sample of triple-mode stars. It is the very first attempt of modelling RR Lyrae stars with non-radial modes. We compared our results with predictions of stellar evolution theory, which resulted in a mass discrepancy more noticeable for long-period stars: Pulsation masses seem higher than evolutionary masses. We compared metallicity estimates for RRc stars from a modelled sample with metallicities determined spectroscopically for a sample of RRc stars in the solar neighbourhood: Both distributions are consistent.
      PubDate: Wed, 29 Jun 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1793
      Issue No: Vol. 515, No. 3 (2022)
       
  • Cold-mode and hot-mode accretion in galaxy formation: an entropy approach

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      Pages: 3453 - 3471
      Abstract: ABSTRACTWe have analysed two cosmological zoom simulations with $M_{\rm vir}\sim 10^{12}{\rm \, M}_\odot$ from the Numerical Investigation of a Hundred Astrophysical Objects (NIHAO) series, both with and without feedback. We show that an entropy criterion based on the equation of state of the intergalactic medium can successfully separate cold- and hot-mode accretion. The shock-heated gas has non-negligible turbulent support and cools inefficiently. In the simulations without feedback, only a small fraction (≲20 per cent) of the stellar mass comes from baryons that have been in the hot circumgalactic medium, although quantitative conclusions should be taken with caution due to our small-number statistics. With feedback, the fraction is larger because of the reaccretion of gas heated by supernovae, which has lower entropies and shorter cooling times than the gas heated by accretion shocks. We have compared the results of NIHAO to predictions of the GalICS 2.1 semi-analytic model of galaxy formation. The shock-stability criterion implemented in GalICS 2.1 successfully reproduces the transition from cold- to hot-mode accretion.
      PubDate: Wed, 06 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1867
      Issue No: Vol. 515, No. 3 (2022)
       
  • Non-solar abundance ratios trends of dEs in the Fornax Cluster using newly
           defined high-resolution indices

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      Pages: 3472 - 3491
      Abstract: ABSTRACTWe perform a detailed study of the stellar populations in a sample of massive Fornax dwarf galaxies using a set of newly defined line indices. Using data from the Integral Field Spectroscopic data, we study abundance ratios of eight dEs with stellar mass ranging from 108 to 109.5 M⊙ in the Fornax Cluster. We present the definitions of a new set of high-resolution Lick-style indices to be used for stellar population studies of unresolved small stellar systems. We identify 23 absorption features and continuum regions, mainly dominated by 12 elements (Na, Ca, Sc, Ti, V, Cr, Mn, Fe, Ni, Y, Ba, and Nd) in the wavelength range 4700–5400 Å and characterize them as a function of age, metallicity, and alpha element abundance ratios. We analyse eight dEs and interpret the line strengths, measured in our new high-resolution system of indices, with the aid of stellar population models with high enough spectral resolution. We obtain abundance ratio proxies for a number of elements that have never been studied before for dwarf ellipticals outside the Local Group. These proxies represent relative deviations from predicted index strengths of base stellar population models built-up following the abundance pattern of The Galaxy. The abundance proxy trend results are compared to abundance ratios from resolved stars in the Local Group, and indices from integrated light of larger early-type galaxies. We find that all our dwarfs show a pattern of abundance ratios consistent with the disc of the Milky Way, indicative of slow formation in comparison to their high-mass counterparts.
      PubDate: Wed, 03 Aug 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1880
      Issue No: Vol. 515, No. 3 (2022)
       
  • Hydromagnetic waves in an expanding universe – cosmological MHD code
           tests using analytic solutions

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      Pages: 3492 - 3511
      Abstract: ABSTRACTWe describe how analytic solutions for linear hydromagnetic waves can be used for testing cosmological magnetohydrodynamic (MHD) codes. We start from the comoving MHD equations and derive analytic solutions for the amplitude evolution of linear hydromagnetic waves in a matter-dominated, flat Einstein-de-Sitter (EdS) universe. The waves considered are comoving, linearly polarized Alfvén waves and comoving, magnetosonic (fast) waves modified by self-gravity. The solution for compressible waves is found for a general adiabatic index and we consider the limits of hydrodynamics without self-gravity in addition to the full solution. In addition to these analytic solutions, the linearized equations are solved numerically for a Λ cold dark matter cosmology. We use the analytic and numeric solutions to compare with results obtained using the cosmological MHD code arepo and find good agreement when using a sufficient number of grid points. We interpret the numerical damping clearly evident in simulations with few grid points by further deriving the Alfvén wave solution including physical Navier–Stokes viscosity. A comparison between Alfvén wave simulations and theory reveals that the dissipation can be described by a numerical viscosity coefficient ηnum ∝ a−5/2, where a is the scale factor. We envision that our examples could be useful when developing a new cosmological MHD code or for regression testing of existing codes.
      PubDate: Mon, 11 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1882
      Issue No: Vol. 515, No. 3 (2022)
       
  • Heat storage in ocean worlds: The role of slurries

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      Pages: 3512 - 3523
      Abstract: ABSTRACTSeveral icy moons of the Solar system, such as Europa, harbor global oceans below their surfaces. It is conceivable that a number of exoplanetary bodies may also possess them. The presence of aqueous layers, partially or totally liquid, highly influences the bulk physical properties of these bodies, particularly the thermal state, and consequently, the geological activity and the potential habitability over time. In this work, we obtained experimental data to characterize the thermal budgets of aqueous environments in planetary bodies depending on the main solute composition, and we quantified the heat associated with water-rich materials’ phase transitions occurring during planetary evolution. We measured the heat capacity (Cp) and the sensible heat values of aqueous systems at several concentrations of sulfate, carbonate, chloride, ammonia, and methanol at low temperatures, and we calculated the latent heat associated with the phase transitions. Raman spectroscopy allowed us to identify the phases related to the Cp and enthalpy (ΔH) variations. We applied thermal functions to estimate the energy involved in the generation of oceans and other endogenous processes, recognizing the impact of heat transfer by both ice and brine slurries. Likewise, we calculated the heat associated with the formation of local liquid lenses, particularly below Europa’s surface, which is suggested by the presence of geological features such as Thera Macula. We propose that the calorimetric properties of the slurries of the studied salt- and volatile-systems may sustain the potential habitability of icy moons and support the formation of certain surface features, in particular due to the high latent heat density and the promotion of the exothermic local growth of ice blocks that can separate from the remaining liquid.
      PubDate: Sat, 23 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1893
      Issue No: Vol. 515, No. 3 (2022)
       
  • Astrochemical model to study the abundances of branched carbon-chain
           molecules in a hot molecular core with realistic binding energies

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      Pages: 3524 - 3538
      Abstract: ABSTRACTStraight-chain (normal-propyl cyanide, $\rm {n-C_3H_7CN}$) and branched-chain (iso-propyl cyanide, $\rm {i-C_3H_7CN}$) alkyl cyanides are recently identified in the massive star-forming regions (Sgr B2(N) and Orion). These branched-chain molecules indicate that the key amino acids (side-chain structures) may also be present in a similar region. The process by which this branching could propagate towards the higher order (butyl cyanide, $\rm {C_4H_9CN}$) is an active field of research. Since the grain catalysis process could have formed a major portion of these species, considering a realistic set of binding energies are indeed essential. We employ quantum chemical calculations to estimate the binding energy of these species considering water as a substrate because water is the principal constituent of this interstellar ice. We find significantly lower binding energy values for these species than were previously used. It is noticed that the use of realistic binding energy values can significantly change the abundance of these species. The branching is more favourable for the higher order alkyl cyanides with the new binding energies. With the inclusion of our new binding energy values and one essential destruction reaction ($\rm {i-C_3H_7CN+H \rightarrow CH_3C(CH_3)CN + H_2}$, having an activation barrier of 947 K), abundances of $\rm {t-C_4H_9CN}$ dramatically increased.
      PubDate: Wed, 03 Aug 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1904
      Issue No: Vol. 515, No. 3 (2022)
       
  • Universal relations for rapidly rotating cold and hot hybrid stars

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      Pages: 3539 - 3554
      Abstract: ABSTRACTSeveral global parameters of compact stars are related via empirical relations, which are (nearly) independent of the underlying equation of state (EoS) of dense matter and, therefore, are said to be universal. We investigate the universality of relations that express the maximum mass and the radius of non-rotating and maximally rapidly rotating configurations, as well as their moment of inertia, in terms of the compactness of the star. For this, we first utilize a collection of cold (zero-temperature) and hot (isentropic) nucleonic EoS and confirm that the universal relations are holding for our collection of EoS. We then go on, to add to our collection and test for the same universality models of EoS that admit a strong first-order phase transition from nucleonic to deconfined quark matter. Also in this case we find that the universal relations hold, in particular for hot, isentropic hybrid stars. By fitting the universal relations to our computed data, we determine the coefficients entering these relations and the accuracy to which they hold.
      PubDate: Sat, 23 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1916
      Issue No: Vol. 515, No. 3 (2022)
       
  • Spatially resolved gas-phase metallicity in FIRE-2 dwarfs: late-time
           evolution of metallicity relations in simulations with feedback and
           mergers

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      Pages: 3555 - 3576
      Abstract: ABSTRACTWe present an analysis of spatially resolved gas-phase metallicity relations in five dwarf galaxies ($\rm \mathit{M}_{halo} \approx 10^{11}\, {\rm M}_\odot$, $\rm \mathit{M}_\star \approx 10^{8.8}{-}10^{9.6}\, {\rm M}_\odot$) from the FIRE-2 (Feedback in Realistic Environments) cosmological zoom-in simulation suite, which include an explicit model for sub-grid turbulent mixing of metals in gas, near z ≈ 0, over a period of 1.4 Gyr, and compare our findings with observations. While these dwarf galaxies represent a diverse sample, we find that all simulated galaxies match the observed mass–metallicity (MZR) and mass–metallicity gradient (MZGR) relations. We note that in all five galaxies, the metallicities are effectively identical between phases of the interstellar medium (ISM), with 95 ${{\ \rm per\ cent}}$ of the gas being within ±0.1 dex between the cold and dense gas (T < 500 K and nH > 1 cm−3), ionized gas (near the H αT ≈ 104 K ridge-line), and nebular regions (ionized gas where the 10 Myr-averaged star formation rate is non-zero). We find that most of the scatter in relative metallicity between cold dense gas and ionized gas/nebular regions can be attributed to either local starburst events or metal-poor inflows. We also note the presence of a major merger in one of our galaxies, m11e, with a substantial impact on the metallicity distribution in the spatially resolved map, showing two strong metallicity peaks and triggering a starburst in the main galaxy.
      PubDate: Mon, 18 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1958
      Issue No: Vol. 515, No. 3 (2022)
       
  • Arecibo observations of a burst storm from FRB 20121102A in 2016

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      Pages: 3577 - 3596
      Abstract: ABSTRACTFRB 20121102A is the first known fast radio burst (FRB) from which repeat bursts were detected, and one of the best-studied FRB sources in the literature. Here we report on the analysis of 478 bursts (333 previously unreported) from FRB 20121102A using the 305-m Arecibo telescope – detected during approximately 59 hours of observations between December 2015 and October 2016. The majority of bursts are from a burst storm around September 2016. This is the earliest available sample of a large number of FRB 20121102A bursts, and it thus provides an anchor point for long-term studies of the source’s evolving properties. We observe that the bursts separate into two groups in the width-bandwidth-energy parameter space, which we refer to as the low-energy bursts (LEBs) and high-energy bursts (HEBs). The LEBs are typically longer duration and narrower bandwidth than the HEBs, reminiscent of the spectro-temporal differences observed between the bursts of repeating and non-repeating FRBs. We fit the cumulative burst rate-energy distribution with a broken power law and find that it flattens out toward higher energies. The sample shows a diverse zoo of burst morphologies. Notably, burst emission seems to be more common at the top than the bottom of our 1150–1730 MHz observing band. We also observe that bursts from the same day appear to be more similar to each other than to those of other days, but this observation requires confirmation. The wait times and burst rates that we measure are consistent with previous studies. We discuss these results, primarily in the context of magnetar models.
      PubDate: Fri, 22 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1960
      Issue No: Vol. 515, No. 3 (2022)
       
  • Modelling the light curve of Type IIn-P SN 2005cl with red supergiant
           progenitors featuring pre-SN outbursts

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      Pages: 3597 - 3602
      Abstract: ABSTRACTAll Type IIn supernovae (SNe IIn) show narrow hydrogen emission lines in their spectra. Apart from this common feature, they demonstrate very broad diversity in brightness, duration, and morphology of their light curves, which indicates that they likely come from a variety of progenitor systems and explosion channels. A particular subset of SNe IIn, the so-called SNe IIn-P, exhibit ∼100 d plateau phases that are very similar to the ones of the ordinary hydrogen-rich SNe (SNe II). In the past, SNe IIn-P were explained by the models of sub-energetic electron capture explosions surrounded by dense extended winds. In this work, we attempt to explain this class of SNe with standard red supergiant progenitors that experience outbursts several months before the final explosion. The outburst energies that show the best agreement between our models and the data ($5\times 10^{46}\, {\rm erg}$) fall at the low range of the outburst energies that have been observed for SNe IIn (between few times $10^{46}\, {\rm erg}$ and $10^{49}\, {\rm erg}$). Instead, the inferred explosion energy of SN 2005cl is relatively high ($1{-}2\times 10^{51}\, {\rm erg}$) compared to the explosion energies of the ordinary SNe II. Our models provide alternative explanation of SNe IIn-P to the previously proposed scenarios.
      PubDate: Sat, 23 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1970
      Issue No: Vol. 515, No. 3 (2022)
       
  • Redshift and stellar mass dependence of intrinsic shapes of disc-dominated
           galaxies from COSMOS observations below z = 1.0

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      Pages: 3603 - 3631
      Abstract: ABSTRACTThe high abundance of disc galaxies without a large central bulge challenges predictions of current hydrodynamic simulations of galaxy formation. We aim to shed light on the formation of these objects by studying the redshift and mass dependence of their intrinsic 3D shape distributions in the COSMOS galaxy survey below redshift z = 1.0. This distribution is inferred from the observed distribution of 2D shapes, using a reconstruction method which we test using hydrodynamic simulations. Our tests reveal a moderate bias for the inferred average disc circularity and relative thickness, but a large bias on the dispersion of these quantities. Applying the reconstruction method on COSMOS data, we find variations of the average disc circularity and relative thickness with redshift of around ∼1 per cent and ∼10 per cent, respectively, which is comparable to the error estimates on these quantities. The average relative disc thickness shows a significant mass dependence which can be accounted for by the scaling of disc radius with galaxy mass. We conclude that our data provides no evidence for a strong dependence of the average circularity and absolute thickness of disc-dominated galaxies on redshift and mass that is significant with respect to the statistical uncertainties in our analysis. These findings are expected in the absence of disruptive merging or feedback events that would affect galaxy shapes. They hence support a scenario where present-day discs form early ( z > 1.0) and subsequently undergo a tranquil evolution in isolation. However, more data and a better understanding of systematics are needed to reaffirm our results.
      PubDate: Fri, 22 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1988
      Issue No: Vol. 515, No. 3 (2022)
       
  • Optical counterparts of ULXs in NGC 1672

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      Pages: 3632 - 3643
      Abstract: ABSTRACTIn this work, we deploy archival data from Hubble Space Telescope, Chandra, XMM–Newton, and Swift-XRT, to probe the nature of nine candidate ultraluminous X-ray sources (ULXs) in NGC 1672. Specifically, our study focuses on using the precise source positions obtained via improved astrometry based on Chandra and Hubble Space Telescope observations to search for and identify potential optical counterparts for these ULXs. Unique optical counterparts are identified for two of the ULX candidates, i.e. X2 and X6; for three of the candidates, i.e. X1, X5, and X7, we found two potential counterparts for each source within the respective error radii. No optical counterparts were found for the remaining four sources. The spectral energy distribution of X2 is fitted to a blackbody spectrum with a temperature of ∼104 K and the spectral class of the source is determined to be B7−A3, a supergiant donor star. We used colour–magnitude diagrams to investigate ages of the counterparts. Of all the sources studied, X9 exhibits the most variability whereby the X-ray flux varies by a factor of ∼50 over a time period spanning 2004–2019, and also traces a partial q-curve-like feature in the hardness–intensity diagram, hinting at possible spectral transitions.
      PubDate: Thu, 21 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1992
      Issue No: Vol. 515, No. 3 (2022)
       
  • An orientation bias in observations of submillimetre galaxies

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      Pages: 3644 - 3655
      Abstract: ABSTRACTRecent high-resolution interferometric images of submillimetre galaxies (SMGs) reveal fascinatingly complex morphologies. This raises a number of questions: how does the relative orientation of a galaxy affect its observed submillimetre emission, and does this result in an ‘orientation bias’ in the selection and analysis of such galaxies in flux-limited cosmological surveys' We investigated these questions using the simba cosmological simulation paired with the dust radiative transfer code powderday. We selected eight simulated SMGs (S850 ≳ 2 mJy) at z = 2, and measured the variance of their ‘observed’ emission over 50 random orientations. Each galaxy exhibits significant scatter in its emission close to the peak of the thermal dust emission, with variation in flux density of up to a factor of 2.7. This results in an appreciable dispersion in the inferred dust temperatures and infrared luminosities (16th–84th percentile ranges of 5 K and 0.1 dex, respectively) and therefore a fundamental uncertainty in derived parameters such as dust mass and star formation rate (∼30 per cent for the latter using simple calibrations). Using a Monte Carlo simulation we also assessed the impact of orientation on flux-limited surveys, finding a bias in the selection of SMGs towards those with face-on orientations, as well as those at lower redshifts. We predict that the orientation bias will affect flux-limited single-dish surveys, most significantly at THz frequencies, and this bias should be taken into account when placing the results of targeted follow-up studies in a statistical context.
      PubDate: Thu, 28 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac2008
      Issue No: Vol. 515, No. 3 (2022)
       
  • Constraining IGM enrichment and metallicity with the C iv forest
           correlation function

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      Pages: 3656 - 3673
      Abstract: ABSTRACTThe distribution and abundance of metals in the diffuse intergalactic medium (IGM) have implications for galaxy formation and evolution models, and has been argued to be sensitive to the Universe’s reionization history. However, reduced sensitivity in the near-IR implies that probing IGM metals at z > 4 is currently out of reach with the traditional method of detecting individual absorbers. We present a new technique based on clustering analysis that enables the detection of these weak IGM absorbers. We investigate the two-point correlation function (2PCF) of the ${\rm C\, {\small IV}}$ forest as a probe of IGM metallicity and enrichment topology by simulating the z = 4.5 IGM with models of inhomogeneous metal distributions. The 2PCF of the ${\rm C\, {\small IV}}$ forest demonstrates a clear peak at a characteristic separation corresponding to the doublet separation of the ${\rm C\, {\small IV}}$ line.The peak amplitude scales quadratically with metallicity, while enrichment topology affects both the shape and amplitude of the 2PCF. For models consistent with the distribution of metals at z ∼ 3, we find that we can constrain [C/H] to within 0.2 dex, log$\, M_{\rm {min}}$ to within 0.4 dex, and R to within 15 per cent. We show that CGM absorbers can be reliably identified and masked, thus recovering the underlying IGM signal. The auto-correlation of the metal-line forest presents a compelling avenue to constrain the IGM metallicity and enrichment topology with high precision at z > 4, thereby pushing such measurements into the Epoch of Reionization.
      PubDate: Wed, 03 Aug 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac2021
      Issue No: Vol. 515, No. 3 (2022)
       
  • A major galaxy cluster merger caught by eROSITA: weak lensing mass
           distribution and kinematic description

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      Pages: 3674 - 3684
      Abstract: ABSTRACTWe present the weak lensing mass distribution of a triple merging cluster candidate at zphoto ∼ 0.36 belonging to a supercluster recently discovered during the eROSITA Performance Verification phase. Our analysis solved a previous tension in the merger classification by confirming that the cluster pair eFEDS J093513.3+004746 and eFEDS J093510.7+004910 is undergoing a major merger with a mass ratio $1.7_{-0.7}^{+0.5}$. According to our two-body kinematic description, the encounter happened $0.58_{-0.20}^{+0.15}$ Gyr ago, in a scenario that supports the observed radio relic position at the cluster outskirts. However, the same analysis showed that the companion cluster, eFEDS J093501.1+005418, is not gravitationally bound to the interacting system and therefore it is not part of the supercluster. We also checked the impact of adopting a scaling relation to determine the halo concentration c200. At the observed merger stage, where the clusters have travelled ∼55 per cent of the path to reach the apoapsis, the choice of c200 (whether from a scaling relation or a free parameter in the mass model) does not change significantly either the cluster masses or the kinematic description.
      PubDate: Mon, 08 Aug 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac2053
      Issue No: Vol. 515, No. 3 (2022)
       
  • Satellite mass functions and the faint end of the galaxy mass–halo
           mass relation in LCDM

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      Pages: 3685 - 3697
      Abstract: ABSTRACTThe abundance of the faintest galaxies provides insight into the nature of dark matter and the process of dwarf galaxy formation. In the LCDM scenario, low-mass haloes are so numerous that the efficiency of dwarf formation must decline sharply with decreasing halo mass in order to accommodate the relative scarcity of observed dwarfs and satellites in the Local Group. The nature of this decline contains important clues to the mechanisms regulating the onset of galaxy formation in the faintest systems. We explore here two possible models for the stellar mass (M*)–halo mass (M200) relation at the faint end, motivated by some of the latest LCDM cosmological hydrodynamical simulations. One model includes a sharp mass threshold below which no luminous galaxies form, as expected if galaxy formation proceeds only in systems above the hydrogen-cooling limit. In the second model, M* scales as a steep power law of M200 with no explicit cut-off, as suggested by recent semi-analytical work. Although both models predict satellite numbers around Milky Way-like galaxies consistent with current observations, they predict vastly different numbers of ultrafaint dwarfs and of satellites around isolated dwarf galaxies. Our results illustrate how the satellite mass function around dwarfs may be used to probe the M*–M200 relation at the faint end and to elucidate the mechanisms that determine which low-mass haloes ‘light up’ or remain dark in the LCDM scenario.
      PubDate: Sat, 23 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac2057
      Issue No: Vol. 515, No. 3 (2022)
       
  • Four new fast radio bursts discovered in the Parkes 70-cm pulsar survey
           archive

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      Pages: 3698 - 3702
      Abstract: ABSTRACTWe present four new fast radio bursts discovered in a search of the Parkes 70-cm pulsar survey data archive for dispersed single pulses and bursts. We searched dispersion measures (DMs) ranging between 0 and 5000 pc cm−3 with the HEIMDALL and FETCH detection and classification algorithms. All four of the fast radio bursts (FRBs) discovered have significantly larger widths (>50 ms) than almost all of the FRBs detected and catalogued to date. The large pulse widths are not dominated by interstellar scattering or dispersive smearing within channels. One of the FRBs has a DM of 3338 pc cm3, the largest measured for any FRB to date. These are also the first FRBs detected by any radio telescope so far, predating the Lorimer Burst by almost a decade. Our results suggest that pulsar survey archives remain important sources of previously undetected FRBs and that searches for FRBs on time-scales extending beyond ∼100 ms may reveal the presence of a larger population of wide-pulse FRBs.
      PubDate: Mon, 01 Aug 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac2101
      Issue No: Vol. 515, No. 3 (2022)
       
  • The late-time light curves of Type Ia supernovae: confronting models with
           observations

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      Pages: 3703 - 3715
      Abstract: ABSTRACTType Ia supernovae (SNe Ia) play a crucial role as standardizable candles in measurements of the Hubble constant and dark energy. Increasing evidence points towards multiple possible explosion channels as the origin of normal SNe Ia, with possible systematic effects on the determination of cosmological parameters. We present, for the first time, a comprehensive comparison of publicly available SN Ia model nucleosynthetic data with observations of late-time light curve observations of SN Ia events. These models span a wide range of white dwarf (WD) progenitor masses, metallicities, explosion channels, and numerical methodologies. We focus on the influence of 57Ni and its isobaric decay product 57Co in powering the late-time (t > 1000 d) light curves of SNe Ia. 57Ni and 57Co are neutron-rich relative to the more abundant radioisotope 56Ni, and are consequently a sensitive probe of neutronization at the higher densities of near-Chandrashekhar (near-MCh) progenitor WDs. We demonstrate that observations of one SN Ia event, SN 2015F is only consistent with a sub-Chandrasekhar (sub-MCh) WD progenitor. Observations of four other events (SN 2011fe, SN 2012cg, SN 2014J, and SN2013aa) are consistent with both near-MCh and sub-MCh progenitors. Continued observations of late-time light curves of nearby SNe Ia will provide crucial information on the nature of the SN Ia progenitors.
      PubDate: Mon, 20 Jun 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1618
      Issue No: Vol. 515, No. 3 (2022)
       
  • New, late-type spectroscopic binaries with X-ray emission

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      Pages: 3716 - 3728
      Abstract: ABSTRACTIn this paper, we present a spectroscopic study of six double-lined binaries, five of which were recently discovered in a high-resolution spectroscopic survey of optical counterparts of stellar X-ray sources. Thanks to high-resolution spectra acquired with CAOS spectropolarimeter during 7 yr, we were able to measure the radial velocities of their components and determine their orbital elements. We have applied our code compo2 to determine the spectral types and atmospheric parameters of the components of these spectroscopic binaries and found that two of these systems are composed of main-sequence stars, while the other four contain at least one evolved (giant or subgiant) component, similar to other well-known RS CVn systems. The subtraction of a photospheric template built up with spectra of non-active stars of the same spectral type as those of the components of each system has allowed us to investigate the chromospheric emission that fills in the H α cores. We found that the colder component is normally the one with the largest H α emission. None of the systems show a detectable Li iλ6708 line, with the exception of TYC 4279-1821-1, which exhibits high photospheric abundances in both components. Photometric time-series from the literature allowed us to assess that the five systems with a nearly circular orbit have also photometric periods close or equal to the orbital ones, indicating spin–orbit synchronization. For the system with a highly eccentric orbit, a possible pseudo-synchronization with the periastron velocity is suggested.
      PubDate: Tue, 05 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1850
      Issue No: Vol. 515, No. 3 (2022)
       
  • Consistency study of high- and low-accreting Mg ii quasars: no
           significant effect of the Fe ii to Mg ii flux ratio on the
           radius–luminosity relation dispersion

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      Pages: 3729 - 3748
      Abstract: ABSTRACTWe use observations of 66 reverberation-measured Mg ii quasars (QSOs) in the redshift range 0.36 ≤ z ≤ 1.686 – a subset of the 78 QSOs we previously studied that also have ${\cal R}_{\rm {Fe\, {\small II}}}$ (flux ratio parameter of UV Fe ii to Mg ii that is used as an accretion-rate proxy) measurements – to simultaneously constrain cosmological model parameters and QSO two-parameter and three-parameter radius–luminosity (R–L) relation parameters in six different cosmological models. We find that these QSO R–L relation parameters are independent of the assumed cosmological model and so these QSOs are standardizable through the R–L relations. Also: (1) With the two-parameter R–L relation, we find that the low-${\cal R}_{\rm {Fe\, {\small II}}}$ and high-${\cal R}_{\rm {Fe\, {\small II}}}$ data subsets obey the same R–L relation within the error bars. (2) Extending the two-parameter R–L relation to a three-parameter one does not result in the hoped-for reduction in the intrinsic dispersion of the R–L relation. (3) Neither of the three-parameter R–L relations provide a significantly better fit to the measurements than does the two-parameter R–L relation. These are promising results for the ongoing development of Mg ii cosmological probes. The first and third of these results differ significantly from those we found elsewhere from analyses of reverberation-measured H β QSOs.
      PubDate: Tue, 12 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1940
      Issue No: Vol. 515, No. 3 (2022)
       
  • Correlations between X-ray spectral parameters of Mkn 421 using
           long-term Swift–XRT data

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      Pages: 3749 - 3759
      Abstract: ABSTRACTWe have performed a detailed analysis of the X-ray spectra of the blazar Mkn 421 using Swift–XRT observations taken between 2005 and 2020, to quantify the correlations between spectral parameters for different models. In an earlier work, it has been shown that such spectral parameter correlations obtained from a single short flare of duration ∼5 d of Mkn 421, can be used to distinguish spectrally degenerate models and provide estimates of physical quantities. In this work, we show that the results from the long-term spectral parameter correlations are consistent with those obtained from the single flare. In particular, that the observed spectral curvature is due to maximum cut-off energy in the particle distribution is ruled out. Instead, models where the curvature is due to the energy dependence of escape or acceleration time-scale of the particles are favoured. The estimated values of the physical parameters for these models are similar to the ones obtained from the single flare analysis and are somewhat incompatible with the physical assumption of the models, suggesting that more complex physical models are required. The consistency of the results obtained from the long- and short-term evolution of the source, underlines the reliability of the technique to use spectral parameter correlations to distinguish physical models.
      PubDate: Mon, 25 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1964
      Issue No: Vol. 515, No. 3 (2022)
       
  • Characterization of acetonitrile ice irradiated by X-rays employing the
           procoda code – I. Effective rate constants and abundances at chemical
           equilibrium

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      Pages: 3760 - 3772
      Abstract: ABSTRACTIn this work, the chemical evolution of pure acetonitrile ice at 13 K irradiated with broad-band soft X-rays (from 6 eV to 2 keV) is determined by using a computational methodology (procoda code) to best fit the experimental data. To simulate the chemical evolution of the acetonitrile ice under an astrophysical analogous situation, the code employs 273 reaction rates involving 33 molecular species (5 species observed in the experiment and 28 non-observed or unknown). The considered reaction network describes 240 chemical reactions (including dissociation, bimolecular, and termolecular rates) and 33 individual desorption rates. The summed desorption yield was determined to be 0.23 molecules per photon, in agreement with previous estimates. Average values for dissociation, bimolecular, and termolecular effective rate constants were determined as 2.3 × 10−3 s−1, 9.7 × 10−26 cm3 molecule−1 s−1, and 3.2 × 10−47 cm6 molecule−2 s−1, respectively. Some branching ratios within reaction groups were also determined. Molecular abundances at chemical equilibrium were obtained, such as CH3CN (67.5 per cent), H (10.6 per cent), CN (6.7 per cent), CH2 (6.4 per cent), CH (2.5 per cent), CH3 (1.2 per cent), CH4 (1.1 per cent), C2N2 (0.8 per cent), HCN (0.8 per cent), and CH3NC (0.6 per cent). The results of this work can be employed in future astrochemical models to map chemical evolution embedded species in astrophysical regions in the presence of an ionizing radiation field.
      PubDate: Thu, 14 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1965
      Issue No: Vol. 515, No. 3 (2022)
       
  • Von Zeipel – Lidov – Kozai cycles in action: Kepler triples with
           eclipse depth variations: KICs 6964043, 5653126, 5731312, and 8023317

    • Free pre-print version: Loading...

      Pages: 3773 - 3795
      Abstract: ABSTRACTWe report the results of the photodynamical analyses of four compact, tight triple stellar systems, KICs 6964043, 5653126, 5731312, and 8023317, based largely on Kepler and TESS data. All systems display remarkable eclipse timing and eclipse depth variations, the latter implying a non-aligned outer orbit. Moreover, KIC 6964043 is also a triply eclipsing system. We combined photometry, ETV curves, and archival spectral energy distribution data to obtain the astrophysical parameters of the constituent stars and the orbital elements with substantial precision. KICs 6964043 and 5653126 were found to be nearly flat with mutual inclinations imut = 4${_{.}^{\circ}}$1 and 12${_{.}^{\circ}}$3, respectively, while KICs 5731312 and 8023317 (imut = 39${_{.}^{\circ}}$4 and 55${_{.}^{\circ}}$7, respectively) are found to lie in the high imut regime of the von Zeipel-Kozai-Lidov (ZKL) theorem. We show that, currently, both high inclination triples exhibit observable unusual retrograde apsidal motion. Moreover, the eclipses will disappear in all but one of the four systems within a few decades. Short-term numerical integrations of the dynamical evolution reveal that both high inclination triples are currently subject to ongoing, large amplitude (Δe ∼ 0.3) inner eccentricity variations on centuries-long time-scales, in accord with the ZKL theorem. Longer-term integrations predict that two of the four systems may become dynamically unstable on ∼ Gyr time-scales, while in the other two triples common envelope phases and stellar mergers may occur. Finally, we investigate the dynamical properties of a sample of 71 KIC/TIC triples statistically, and find that the mutual inclinations and outer mass ratios are anticorrelated at the 4σ level. We discuss the implications for the formation mechanisms of compact triples.
      PubDate: Fri, 22 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1983
      Issue No: Vol. 515, No. 3 (2022)
       
  • Double flows anchored in a Kerr black hole horizon – I. Meridionally
           self-similar MHD models with loading terms

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      Pages: 3796 - 3817
      Abstract: ABSTRACTRecent observations of supermassive black holes have brought us new information on their magnetospheres. In this study, we attempt a theoretical modelling of the coupling of black holes with their jets and discs, via three innovations. First, we propose a semi-analytical MHD description of a steady relativistic inflow–outflow structure characteristic to the extraction of the hole rotational energy. The mass-loading is ensured in a thin layer, the stagnation surface, by a two-photon pair production originating to a gamma-ray emission from the surrounding disc. The double flow is described near the polar axis by an axisymmetric meridionally self-similar MHD model. Secondly, the inflow and outflow solutions are crossing the MHD critical points and are matched at the stagnation surface. Knowledge of the MHD field on the horizon gives us the angular momentum and energy extracted from the black hole. Finally, we illustrate the model with three specific examples of double-flow solutions by varying the energetic interaction between the MHD field and the rotating black hole. When the isorotation frequency is half of the black hole one, the extracted Poynting flux is comparable to the one obtained using the force-free assumption. In two of the presented solutions, the Penrose process dominates at large colatitudes, while the third is Poynting flux dominated at mid-colatitudes. Mass injection rate estimations, from disc luminosity and inner radius, give an upper limit just above the values obtained for two solutions. This model is pertinent to describe the flows near the polar axis, where pair production is more efficient.
      PubDate: Wed, 27 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1990
      Issue No: Vol. 515, No. 3 (2022)
       
  • Machine learning for galactic archaeology: a chemistry-based neural
           network method for identification of accreted disc stars

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      Pages: 3818 - 3837
      Abstract: ABSTRACTWe develop a method (‘Galactic Archaeology Neural Network’, gann) based on neural network models (NNMs) to identify accreted stars in galactic discs by only their chemical fingerprint and age, using a suite of simulated galaxies from the Auriga Project. We train the network on the target galaxy’s own local environment defined by the stellar halo and the surviving satellites. We demonstrate that this approach allows the detection of accreted stars that are spatially mixed into the disc. Two performance measures are defined – recovery fraction of accreted stars, frecov and the probability that a star with a positive (accreted) classification is a true-positive result, P(TP). As the NNM output is akin to an assigned probability (Pa), we are able to determine positivity based on flexible threshold values that can be adjusted easily to refine the selection of presumed-accreted stars. We find that  gann identifies accreted disc stars within simulated galaxies, with high frecov and/or high P(TP). We also find that stars in Gaia–Enceladus–Sausage (GES) mass systems are over 50 per cent recovered by our NNMs in the majority (18/24) of cases. Additionally, nearly every individual source of accreted stars is detected at 10 per cent or more of its peak stellar mass in the disc. We also demonstrate that a conglomerated NNM, trained on the halo and satellite stars from all of the Auriga galaxies provides the most consistent results, and could prove to be an intriguing future approach as our observational capabilities expand.
      PubDate: Fri, 22 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac2027
      Issue No: Vol. 515, No. 3 (2022)
       
  • Outflows and spectral evolution in the eclipsing AMXP SWIFT J1749.4–2807
           with NICER, XMM-Newton, and NuSTAR

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      Pages: 3838 - 3852
      Abstract: ABSTRACTThe neutron star low-mass X-ray binary SWIFT J1749.4–2807 is the only known eclipsing accreting millisecond X-ray pulsar. In this manuscript, we perform a spectral characterization of the system throughout its 2021, 2-week-long outburst, analysing 11 NICER observations and quasi-simultaneous XMM-Newton and NuSTAR single observations at the outburst peak. The broad-band spectrum is well-modelled with a blackbody component with a temperature of ∼0.6 keV, most likely consistent with a hotspot on the neutron star surface, and a Comptonization spectrum with power-law index Γ ∼ 1.9, arising from a hot corona at ∼12 keV. No direct emission from the disc was found, possibly due to it being too cool. A high truncation radius for the disc, i.e. at ∼20–30 RG, was obtained from the analysis of the broadened profile of the Fe line in the reflection component. The significant detection of a blue-shifted Fe XXVI absorption line at ∼7 keV indicates weakly relativistic X-ray disc winds, which are typically absent in the hard state of X-ray binaries. By comparing the low flux observed during the outburst and the one expected in a conservative mass-transfer, we conclude that mass-transfer in the system is highly non-conservative, as also suggested by the wind detection. Finally, using the NICER spectra alone, we followed the system while it was fading to quiescence. During the outburst decay, as the spectral shape hardened, the hotspot on the neutron star surface cooled down and shrank, a trend which could be consistent with the pure power-law spectrum observed during quiescence.
      PubDate: Mon, 25 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac2038
      Issue No: Vol. 515, No. 3 (2022)
       
  • Evolution of dipolar mixed-mode coupling factor in red giant stars: impact
           of buoyancy spike

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      Pages: 3853 - 3866
      Abstract: ABSTRACTMixed modes observed in red giants allow for investigation of the stellar interior structures. One important feature in these structures is the buoyancy spike caused by the discontinuity of the chemical gradient left behind during the first dredge-up. The buoyancy spike emerges at the base of the convective zone in low-luminosity red giants and later becomes a glitch when the g-mode cavity expands to encompass the spike. Here, we study the impact of the buoyancy spike on the dipolar mixed modes using stellar models with different properties. We find that the applicability of the asymptotic formalisms for the coupling factor, q, varies depending on the location of the evanescent zone, relative to the position of the spike. Significant deviations between the value of q inferred from fitting the oscillation frequencies and either of the formalisms proposed in the literature are found in models with a large frequency separation in the interval 5–15 μHz, with evanescent zones located in a transition region that may be thin or thick. However, it is still possible to reconcile q with the predictions from the asymptotic formalisms, by choosing which formalism to use according to the value of q. For stars approaching the luminosity bump, the buoyancy spike becomes a glitch and strongly affects the mode frequencies. Fitting the frequencies without accounting for the glitch leads to unphysical variations in the inferred q, but we show that this is corrected when properly accounting for the glitch in the fitting.
      PubDate: Sat, 23 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac2065
      Issue No: Vol. 515, No. 3 (2022)
       
  • Similarity solutions for a magnetized supercritical accretion disc around
           a rotating object

    • Free pre-print version: Loading...

      Pages: 3867 - 3874
      Abstract: ABSTRACTThe effect of toroidal magnetic fields on a supercritical accretion disc (slim disc) around a rotating object is examined. In this research, it is supposed that angular momentum transport is due to viscous turbulence and the α-prescription is used for the kinematic coefficient of viscosity. Moreover, the general relativistic effects are neglected. The degree of advection that demonstrates the fraction of energy that accretes by matter on to the central object is considered by f parameter. For the steady-state structure of such accretion flows, a set of self-similar solution is presented. Our solutions will include two important non-dimensional parameters β and a. β is the ratio of the magnetic pressure to the gas pressure, the so-called friction of magnetic pressure, which shows the magnetic field strength. The ratio of the angular velocities of the central body and the accretion flow is indicated by the rotating parameter a. The possible combined effects of magnetic field, spin of central object, and degree of advection are investigated. We also show the effect of rotating parameter a on the physical quantities of disc is different for co-rotating and counter-rotating flows. Moreover, by increasing the degree of advection and strength of magnetic field, the behaviour of the radial and angular velocities becomes reversed with respect to a. The model implies that the surface temperature, thickness, and luminosity of disc strongly depend on rotation parameter and strength of magnetic field.
      PubDate: Mon, 25 Jul 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac2074
      Issue No: Vol. 515, No. 3 (2022)
       
  • Galaxy And Mass Assembly: Galaxy Zoo spiral arms and star formation rates

    • Free pre-print version: Loading...

      Pages: 3875 - 3882
      Abstract: ABSTRACTUnderstanding the effect spiral structure has on star formation properties of galaxies is important to complete our picture of spiral structure evolution. Previous studies have investigated connections between spiral arm properties and star formation, but the effect that the number of spiral arms has on this process is unclear. Here, we use the Galaxy And Mass Assembly (GAMA) survey paired with the citizen science visual classifications from the Galaxy Zoo project to explore galaxies’ spiral arm number and how it connects to the star formation process. We use the votes from the GAMA-Kilo Degree Survey Galaxy Zoo classification to investigate the link between spiral arm number and stellar mass, star formation rate, and specific star formation rate (sSFR). We find that galaxies with fewer spiral arms have lower stellar masses and higher sSFRs, while those with more spiral arms tend towards higher stellar masses and lower sSFRs, and conclude that galaxies are less efficient at forming stars if they have more spiral arms. We note how previous studies’ findings may indicate a cause for this connection in spiral arm strength or opacity.
      PubDate: Tue, 09 Aug 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1936
      Issue No: Vol. 515, No. 3 (2022)
       
  • Visualizing the pulsar population using graph theory

    • Free pre-print version: Loading...

      Pages: 3883 - 3897
      Abstract: ABSTRACTThe $P\dot{P}$ diagram is a cornerstone of pulsar research. It is used in multiple ways for classifying the population, understanding evolutionary tracks, identifying issues in our theoretical reach, and more. However, we have been looking at the same plot for more than five decades. A fresh appraisal may be healthy. Is the $P \dot{P}$-diagram the most useful or complete way to visualize the pulsars we know' Here we pose a fresh look at the information we have on the pulsar population. First, we use principal component analysis over magnitudes depending on the intrinsic pulsar’s timing properties (proxies to relevant physical pulsar features), to analyse whether the information contained by the pulsar’s period and period derivative is enough to describe the variety of the pulsar population. Even when the variables of interest depend on P and $\dot{P}$, we show that $P \dot{P}$ are not principal components. Thus, any distance ranking or visualization based only on P and $\dot{P}$ is potentially misleading. Next, we define and compute a properly normalized distance to measure pulsar nearness, calculate the minimum spanning tree of the population, and discuss possible applications. The pulsar tree hosts information about pulsar similarities that go beyond P and $\dot{P}$, and are thus naturally difficult to read from the $P\dot{P}$-diagram. We use this work to introduce the pulsar tree website containing visualization tools and data to allow users to gather information in terms of MST and distance ranking.
      PubDate: Fri, 05 Aug 2022 00:00:00 GMT
      DOI: 10.1093/mnras/stac1997
      Issue No: Vol. 515, No. 3 (2022)
       
 
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