Subjects -> METEOROLOGY (Total: 108 journals)
 Showing 1 - 36 of 36 Journals sorted alphabetically Acta Meteorologica Sinica       (Followers: 3) Advances in Atmospheric Sciences       (Followers: 42) Advances in Climate Change Research       (Followers: 27) Advances in Meteorology       (Followers: 23) Advances in Statistical Climatology, Meteorology and Oceanography       (Followers: 7) Aeolian Research       (Followers: 6) Agricultural and Forest Meteorology       (Followers: 18) American Journal of Climate Change       (Followers: 26) Atmósfera       (Followers: 3) Atmosphere       (Followers: 24) Atmosphere-Ocean       (Followers: 13) Atmospheric and Oceanic Science Letters       (Followers: 10) Atmospheric Chemistry and Physics (ACP)       (Followers: 47) Atmospheric Chemistry and Physics Discussions (ACPD)       (Followers: 14) Atmospheric Environment       (Followers: 71) Atmospheric Environment : X       (Followers: 2) Atmospheric Research       (Followers: 69) Atmospheric Science Letters       (Followers: 35) Boundary-Layer Meteorology       (Followers: 30) Bulletin of Atmospheric Science and Technology       (Followers: 2) Bulletin of the American Meteorological Society       (Followers: 47) Carbon Balance and Management       (Followers: 5) Change and Adaptation in Socio-Ecological Systems       (Followers: 4) Ciencia, Ambiente y Clima       (Followers: 3) Climate       (Followers: 5) Climate Change Economics       (Followers: 14) Climate Change Research Letters       (Followers: 7) Climate Change Responses       (Followers: 8) Climate Dynamics       (Followers: 42) Climate law       (Followers: 6) Climate of the Past (CP)       (Followers: 5) Climate of the Past Discussions (CPD) Climate Policy       (Followers: 33) Climate Research       (Followers: 6) Climate Risk Management       (Followers: 4) Climate Services       (Followers: 3) Climate Summary of South Africa       (Followers: 2) Climatic Change       (Followers: 62) Current Climate Change Reports       (Followers: 4) Developments in Atmospheric Science       (Followers: 27) Dynamics and Statistics of the Climate System       (Followers: 4) Dynamics of Atmospheres and Oceans       (Followers: 15) Earth Perspectives - Transdisciplinarity Enabled Economics of Disasters and Climate Change       (Followers: 3) Energy & Environment       (Followers: 22) Environmental and Climate Technologies       (Followers: 4) Environmental Dynamics and Global Climate Change       (Followers: 6) Frontiers in Climate       (Followers: 2) GeoHazards       (Followers: 1) International Journal of Atmospheric Sciences       (Followers: 21) International Journal of Biometeorology       (Followers: 1) International Journal of Climatology       (Followers: 31) International Journal of Environment and Climate Change       (Followers: 3) International Journal of Image and Data Fusion       (Followers: 2) Journal of Agricultural Meteorology Journal of Applied Meteorology and Climatology       (Followers: 33) Journal of Atmospheric and Oceanic Technology       (Followers: 33) Journal of Atmospheric and Solar-Terrestrial Physics       (Followers: 194) Journal of Atmospheric Chemistry       (Followers: 21) Journal of Climate       (Followers: 53) Journal of Climate Change       (Followers: 3) Journal of Climatology       (Followers: 3) Journal of Hydrology and Meteorology       (Followers: 29) Journal of Hydrometeorology       (Followers: 10) Journal of Integrative Environmental Sciences       (Followers: 4) Journal of Meteorological Research       (Followers: 2) Journal of Meteorology and Climate Science       (Followers: 13) Journal of Space Weather and Space Climate       (Followers: 26) Journal of the Atmospheric Sciences       (Followers: 77) Journal of the Meteorological Society of Japan       (Followers: 5) Journal of Weather Modification       (Followers: 2) Large Marine Ecosystems       (Followers: 1) Mathematics of Climate and Weather Forecasting       (Followers: 6) Mediterranean Marine Science       (Followers: 1) Meteorologica       (Followers: 2) Meteorological Applications       (Followers: 4) Meteorologische Zeitschrift       (Followers: 3) Meteorology and Atmospheric Physics       (Followers: 25) Mètode Science Studies Journal : Annual Review Michigan Journal of Sustainability       (Followers: 1) Modeling Earth Systems and Environment Monthly Notices of the Royal Astronomical Society       (Followers: 13) Monthly Weather Review       (Followers: 33) Nature Climate Change       (Followers: 119) Nature Reports Climate Change       (Followers: 35) Nīvār npj Climate and Atmospheric Science       (Followers: 3) Open Atmospheric Science Journal       (Followers: 2) Open Journal of Modern Hydrology       (Followers: 6) Revista Brasileira de Meteorologia Revista Iberoamericana de Bioeconomía y Cambio Climático Russian Meteorology and Hydrology       (Followers: 3) Space Weather       (Followers: 24) Studia Geophysica et Geodaetica Tellus A       (Followers: 21) Tellus B       (Followers: 20) The Cryosphere (TC)       (Followers: 5) The Cryosphere Discussions (TCD)       (Followers: 4) The Quarterly Journal of the Royal Meteorological Society       (Followers: 26) Theoretical and Applied Climatology       (Followers: 11) Tropical Cyclone Research and Review       (Followers: 1) Urban Climate       (Followers: 4) Weather       (Followers: 19) Weather and Climate Dynamics Weather and Climate Extremes       (Followers: 15) Weather and Forecasting       (Followers: 27) Weatherwise       (Followers: 4) 气候与环境研究       (Followers: 1)
Similar Journals
 Monthly Notices of the Royal Astronomical SocietyJournal Prestige (SJR): 2.346 Citation Impact (citeScore): 4Number of Followers: 13      Hybrid journal (It can contain Open Access articles) ISSN (Print) 0035-8711 - ISSN (Online) 1365-2966 Published by Oxford University Press  [412 journals]
• Mon-735: a new low-mass pre-main-sequence eclipsing binary in
NGC 2264
• Authors: Gillen E; Hillenbrand L, Stauffer J, et al.
Pages: 1531 - 1548
Abstract: ABSTRACTWe present Mon-735, a detached double-lined eclipsing binary (EB) member of the ∼3 Myr old NGC 2264 star-forming region, detected by Spitzer. We simultaneously model the Spitzer light curves, follow-up Keck/HIRES radial velocities, and the system’s spectral energy distribution to determine self-consistent masses, radii, and effective temperatures for both stars. We find that Mon-735 comprises two pre-main-sequence M dwarfs with component masses of M = 0.2918 ± 0.0099 and 0.2661 ± 0.0095 M⊙, radii of R = 0.762 ± 0.022 and 0.748 ± 0.023 R⊙, and effective temperatures of Teff = 3260 ± 73 and 3213 ± 73 K. The two stars travel on circular orbits around their common centre of mass in P = 1.9751388 ± 0.0000050 d. We compare our results for Mon-735, along with another EB in NGC 2264 (CoRoT 223992193), to the predictions of five stellar evolution models. These suggest that the lower mass EB system Mon-735 is older than CoRoT 223992193 in the mass–radius diagram (MRD) and, to a lesser extent, in the Hertzsprung–Russell diagram (HRD). The MRD ages of Mon-735 and CoRoT 223992193 are ∼7–9 and 4–6 Myr, respectively, with the two components in each EB system possessing consistent ages.
PubDate: Fri, 17 Apr 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1016
Issue No: Vol. 495, No. 2 (2020)

• Plasmoid formation in global GRMHD simulations and AGN flares
• Authors: Nathanail A; Fromm C, Porth O, et al.
Pages: 1549 - 1565
Abstract: ABSTRACTOne of the main dissipation processes acting on all scales in relativistic jets is thought to be governed by magnetic reconnection. Such dissipation processes have been studied in idealized environments, such as reconnection layers, which evolve in merging islands and lead to the production of ‘plasmoids’, ultimately resulting in efficient particle acceleration. In accretion flows on to black holes, reconnection layers can be developed and destroyed rapidly during the turbulent evolution of the flow. We present a series of two-dimensional general-relativistic magnetohydrodynamic simulations of tori accreting on to rotating black holes focusing our attention on the formation and evolution of current sheets. Initially, the tori are endowed with a poloidal magnetic field having a multiloop structure along the radial direction and with an alternating polarity. During reconnection processes, plasmoids and plasmoid chains are developed leading to a flaring activity and hence to a variable electromagnetic luminosity. We describe the methods developed to track automatically the plasmoids that are generated and ejected during the simulation, contrasting the behaviour of multiloop initial data with that encountered in typical simulations of accreting black holes having initial dipolar field composed of one loop only. Finally, we discuss the implications that our results have on the variability to be expected in accreting supermassive black holes.
PubDate: Sat, 23 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1165
Issue No: Vol. 495, No. 2 (2020)

• Study of flux-rope characteristics at sub-astronomical-unit distances
using the Helios 1 and 2 spacecraft
• Authors: Raghav A; Gaikwad S, Wang Y, et al.
Pages: 1566 - 1576
Abstract: ABSTRACTMagnetic flux ropes observed as magnetic clouds near 1 au have been extensively studied in the literature and their distinct features are derived using numerous models. These studies summarize the general characteristics of flux ropes at 1 au without providing an understanding of the continuous evolution of the flux ropes from near the Sun to 1 au. In the present study, we investigate 26 flux ropes observed by the Helios 1 and 2 spacecraft (from 0.3 to 1 au) using the velocity-modified Gold–Hoyle model. The correlation and regression analyses suggest that the expansion speed, poloidal speed, total magnetic helicity and twist per au of the flux rope are independent of heliospheric distance. The study implies that the aforementioned features are more strongly influenced by their internal properties compared with external conditions in the ambient medium. Moreover, the poloidal magnetic flux and magnetic energy of the studied flux ropes exhibit power-law dependence on heliospheric distance. A better understanding of the underlying physics and corroboration of these results is expected from the Parker Solar Probe measurements in the near future.
PubDate: Tue, 26 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1189
Issue No: Vol. 495, No. 2 (2020)

• Radiative equilibrium estimates of dust temperature and mass in
high-redshift galaxies
• Authors: Inoue A; Hashimoto T, Chihara H, et al.
Pages: 1577 - 1592
Abstract: ABSTRACTThe estimation of the temperature and mass of dust in high-redshift galaxies is essential for discussions of the origin of dust in the early Universe. However, this is made difficult by limited sampling of the infrared spectral-energy distribution. Here, we present an algorithm for deriving the temperature and mass of dust in a galaxy, assuming dust to be in radiative equilibrium. We formulate the algorithm for three geometries: a thin spherical shell, a homogeneous sphere and a clumpy sphere. We also discuss the effects of the mass absorption coefficients of dust at ultraviolet and infrared wavelengths, κUV and κIR, respectively. As an example, we apply the algorithm to a normal, dusty star-forming galaxy at z = 7.5, A1689zD1, for which three data points in the dust continuum are available. Using κUV = 5.0 × 104 and $\kappa _{\rm IR}=30(\lambda /100\,\mu{\rm m})^{-\beta }$ cm2 g−1 with β = 2.0, we obtain dust temperatures of 38–70 K and masses of 106.5–7.3 M⊙ for the three geometries considered. We obtain similar temperatures and masses from just a single data point in the dust continuum, suggesting that the algorithm is useful for high-redshift galaxies with limited infrared observations. In the case of the clumpy sphere, the temperature becomes equal to that of the usual modified black-body fit, because an additional parameter describing the clumpiness works as an adjuster. The best-fitting clumpiness parameter is ξcl = 0.1, corresponding to ∼10 per cent of the volume filling factor of the clumps in this high-redshift galaxy if the clump size is ∼10 pc, similar to that of giant molecular clouds in the local Universe.
PubDate: Tue, 26 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1203
Issue No: Vol. 495, No. 2 (2020)

• Particle acceleration in low-power hotspots: modelling the broad-band
spectral energy distribution
• Authors: Migliori G; Orienti M, Coccato L, et al.
Pages: 1593 - 1607
PubDate: Mon, 11 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1214
Issue No: Vol. 495, No. 2 (2020)

• The Lyapunov exponents and the neighbourhood of periodic orbits
• Authors: Carpintero D; Muzzio J.
Pages: 1608 - 1612
Abstract: ABSTRACTWe show that the Lyapunov exponents of a periodic orbit can be easily obtained from the eigenvalues of the monodromy matrix. It turns out that the Lyapunov exponents of simply stable periodic orbits are all zero, simply unstable periodic orbits have only one positive Lyapunov exponent, doubly unstable periodic orbits have two different positive Lyapunov exponents, and the two positive Lyapunov exponents of complex unstable periodic orbits are equal. We present a numerical example for periodic orbits in a realistic galactic potential. Moreover, the centre manifold theorem allowed us to show that stable, simply unstable, and doubly unstable periodic orbits are the mothers of families of, respectively, regular, partially, and fully chaotic orbits in their neighbourhood.
PubDate: Sat, 16 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1227
Issue No: Vol. 495, No. 2 (2020)

• Improving galaxy clustering measurements with deep learning: analysis of
the DECaLS DR7 data
• Authors: Rezaie M; Seo H, Ross A, et al.
Pages: 1613 - 1640
Abstract: ABSTRACTRobust measurements of cosmological parameters from galaxy surveys rely on our understanding of systematic effects that impact the observed galaxy density field. In this paper, we present, validate, and implement the idea of adopting the systematics mitigation method of artificial neural networks for modelling the relationship between the target galaxy density field and various observational realities including but not limited to Galactic extinction, seeing, and stellar density. Our method by construction allows a wide class of models and alleviates overtraining by performing k-fold cross-validation and dimensionality reduction via backward feature elimination. By permuting the choice of the training, validation, and test sets, we construct a selection mask for the entire footprint. We apply our method on the extended Baryon Oscillation Spectroscopic Survey (eBOSS) Emission Line Galaxies (ELGs) selection from the Dark Energy Camera Legacy Survey (DECaLS) Data Release 7 and show that the spurious large-scale contamination due to imaging systematics can be significantly reduced by up-weighting the observed galaxy density using the selection mask from the neural network and that our method is more effective than the conventional linear and quadratic polynomial functions. We perform extensive analyses on simulated mock data sets with and without systematic effects. Our analyses indicate that our methodology is more robust to overfitting compared to the conventional methods. This method can be utilized in the catalogue generation of future spectroscopic galaxy surveys such as eBOSS and Dark Energy Spectroscopic Instrument (DESI) to better mitigate observational systematics.
PubDate: Mon, 11 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1231
Issue No: Vol. 495, No. 2 (2020)

• Timing of the accreting millisecond pulsar IGR J17591–2342: evidence of
spin-down during accretion
• Authors: Sanna A; Burderi L, Gendreau K, et al.
Pages: 1641 - 1649
Abstract: ABSTRACTWe report on the phase-coherent timing analysis of the accreting millisecond X-ray pulsar IGR J17591–2342, using Neutron Star Interior Composition Explorer (NICER) data taken during the outburst of the source between 2018 August 15 and 2018 October 17. We obtain an updated orbital solution of the binary system. We investigate the evolution of the neutron star spin frequency during the outburst, reporting a refined estimate of the spin frequency and the first estimate of the spin frequency derivative ($\dot{\nu }\sim -7\times 10^{-14}$ Hz s−1), confirmed independently from the modelling of the fundamental frequency and its first harmonic. We further investigate the evolution of the X-ray pulse phases adopting a physical model that accounts for the accretion material torque as well as the magnetic threading of the accretion disc in regions where the Keplerian velocity is slower than the magnetosphere velocity. From this analysis we estimate the neutron star magnetic field Beq = 2.8(3) × 108 G. Finally, we investigate the pulse profile dependence on energy finding that the observed behaviour of the pulse fractional amplitude and lags as a function of energy is compatible with the down-scattering of hard X-ray photons in the disc or the neutron star surface.
PubDate: Thu, 07 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1253
Issue No: Vol. 495, No. 2 (2020)

• Chemical modelling of dust–gas chemistry within AGB outflows – II.
Effect of the dust-grain size distribution
• Authors: Van de Sande M; Walsh C, Danilovich T.
Pages: 1650 - 1665
Abstract: ABSTRACTAsymptotic giant branch (AGB) stars are, together with supernovae, the main contributors of stellar dust to the interstellar medium (ISM). Dust grains formed by AGB stars are thought to be large. However, as dust nucleation and growth within their outflows are still not understood, the dust-grain size distribution (GSD) is unknown. This is an important uncertainty regarding our knowledge of the chemical and physical history of interstellar dust, as AGB dust forms ${\sim} 70{{\ \rm per\ cent}}$ of the starting point of its evolution. We expand on our chemical kinetics model, which uniquely includes a comprehensive dust–gas chemistry. The GSD is now allowed to deviate from the commonly assumed canonical Mathis, Rumpl & Nordsieck distribution. We find that the specific GSD can significantly influence the dust–gas chemistry within the outflow. Our results show that the level of depletion of gas-phase species depends on the average grain surface area of the GSD. Gas-phase abundance profiles and their possible depletions can be retrieved from observations of molecular emission lines when using a range of transitions. Because of degeneracies within the prescription of GSD, specific parameters cannot be retrieved, only (a lower limit to) the average grain surface area. None the less, this can discriminate between dust composed of predominantly large or small grains. We show that when combined with other observables such as the spectral energy distribution and polarized light, depletion levels from molecular gas-phase abundance profiles can constrain the elusive GSD of the dust delivered to the ISM by AGB outflows.
PubDate: Fri, 08 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1270
Issue No: Vol. 495, No. 2 (2020)

• On building a cluster watchlist for identifying strongly lensed
supernovae, gravitational waves and kilonovae
• Authors: Ryczanowski D; Smith G, Bianconi M, et al.
Pages: 1666 - 1671
Abstract: ABSTRACTMotivated by discovering strongly lensed supernovae, gravitational waves, and kilonovae in the 2020s, we investigate whether to build a watchlist of clusters based on observed cluster properties (i.e. lens-plane selection) or on the detectability of strongly lensed background galaxies (i.e. source-plane selection). First, we estimate the fraction of high-redshift transient progenitors that reside in galaxies that are themselves too faint to be detected as being strongly lensed. We find ∼15–50 per cent of transient progenitors reside in z = 1 − 2 galaxies too faint to be detected in surveys that reach AB ≃ 23, such as the Dark Energy Survey. This falls to ≲10 per cent at depths that will be probed by early data releases of LSST (AB ≃ 25). Secondly, we estimate a conservative lower limit on the fraction of strong-lensing clusters that will be missed by magnitude-limited searches for multiply imaged galaxies and giant arcs due to the faintness of such images. We find that DES-like surveys will miss ∼75 per cent of 1015 M⊙ strong-lensing clusters, rising to ∼100 per cent of 1014 M⊙ clusters. Deeper surveys, such as LSST, will miss ∼40 per cent at 1015 M⊙ and ∼95 per cent at 1014 M⊙. Our results motivate building a cluster watchlist for strongly lensed transients that includes those found by the lens-plane selection.
PubDate: Sat, 09 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1274
Issue No: Vol. 495, No. 2 (2020)

• Photoionizing feedback in spiral arm molecular clouds
• Authors: Bending T; Dobbs C, Bate M.
Pages: 1672 - 1691
Abstract: ABSTRACTWe present simulations of a 500 pc2 region, containing gas of mass 4 × 106 M⊙, extracted from an entire spiral galaxy simulation, scaled up in resolution, including photoionizing feedback from stars of mass >18 M⊙. Our region is evolved for 10 Myr and shows clustered star formation along the arm generating ≈ 5000 cluster sink particles ≈ 5 per cent of which contain at least one of the ≈ 4000 stars of mass >18 M⊙. Photoionization has a noticeable effect on the gas in the region, producing ionized cavities and leading to dense features at the edge of the H ii regions. Compared to the no-feedback case, photoionization produces a larger total mass of clouds and clumps, with around twice as many such objects, which are individually smaller and more broken up. After this we see a rapid decrease in the total mass in clouds and the number of clouds. Unlike studies of isolated clouds, our simulations follow the long-range effects of ionization, with some already dense gas, becoming compressed from multiple sides by neighbouring H ii regions. This causes star formation that is both accelerated and partially displaced throughout the spiral arm with up to 30 per cent of our cluster sink particle mass forming at distances >5 pc from sites of sink formation in the absence of feedback. At later times, the star formation rate decreases to below that of the no-feedback case.
PubDate: Mon, 11 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1293
Issue No: Vol. 495, No. 2 (2020)

• Powering central compact objects with a tangled crustal magnetic field
• Authors: Gourgouliatos K; Hollerbach R, Igoshev A.
Pages: 1692 - 1699
Abstract: ABSTRACTCentral Compact Objects (CCOs) are X-ray sources with luminosity ranging between 1032 and 1034 erg s−1, located at the centres of supernova remnants. Some of them have been confirmed to be neutron stars. Timing observations have allowed the estimation of their dipole magnetic field, placing them in the range ∼1010–1011 G. The decay of their weak dipole fields, mediated by the Hall effect and Ohmic dissipation, cannot provide sufficient thermal energy to power their X-ray luminosity, as opposed to magnetars whose X-ray luminosities are comparable. Motivated by the question of producing high X-ray power through magnetic field decay while maintaining a weak dipole field, we explore the evolution of a crustal magnetic field that does not consist of an ordered axisymmetric structure, but rather comprises a tangled configuration. This can be the outcome of a non-self-excited dynamo, buried inside the crust by fallback material following the supernova explosion. We find that such initial conditions lead to the emergence of the magnetic field from the surface of the star and the formation of a dipolar magnetic field component. An internal tangled magnetic field of the order of 1014 G can provide sufficient Ohmic heating to the crust and power CCOs, while the dipole field it forms is approximately 1010 G, as observed in CCOs.
PubDate: Mon, 11 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1295
Issue No: Vol. 495, No. 2 (2020)

• Lessons on early structure formation from a mature galaxy cluster observed
at cosmic noon
• Authors: Liu B; Schauer A, Bromm V.
Pages: 1700 - 1705
Abstract: ABSTRACTWe demonstrate a new approach of indirectly constraining both early star and structure formation via mature galaxy clusters at cosmic noon (z ∼ 2), using the cluster XLSSC 122 as an example. With the standard Press Schechter formalism, we infer a rapid evolution of the star formation efficiency (the ratio of stellar to halo mass) from 10−4 to 0.01 during z ∼ 20−13, based on the age distribution of stars in post-starburst galaxies of XLSSC 122, measured by Hubble Space Telescope photometry assuming no dust extinction. Here, we consider all low-mass haloes, including minihaloes, that host the first stars and galaxies ($5\times 10^5\ \rm M_{\odot }\lesssim M_{\rm halo}\lesssim 10^{10}\ \rm M_{\odot }$). We also place new constraints on fuzzy dark matter models of ma ≲ 5 × 10−21 eV/c2 for the ultralight boson mass, from the abundance of galaxies with star formation at z ≳ 13 in XLSSC 122. Our exploratory results are consistent with existing constraints. More comprehensive results will be obtained if our approach is extended to a large sample of clusters or field post-starburst galaxies at cosmic noon, with improved modelling of halo and stellar populations.
PubDate: Mon, 11 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1307
Issue No: Vol. 495, No. 2 (2020)

• SuperCLASS – I. The super cluster assisted shear survey: Project
overview and data release 1
• Authors: Battye R; Brown M, Casey C, et al.
Pages: 1706 - 1723
Abstract: ABSTRACTThe SuperCLuster Assisted Shear Survey (SuperCLASS) is a legacy programme using the e-MERLIN interferometric array. The aim is to observe the sky at L-band (1.4 GHz) to a r.m.s. of $7\, \mu {\rm Jy}\,$beam−1 over an area of $\sim 1\, {\rm deg}^2$ centred on the Abell 981 supercluster. The main scientific objectives of the project are: (i) to detect the effects of weak lensing in the radio in preparation for similar measurements with the Square Kilometre Array (SKA); (ii) an extinction free census of star formation and AGN activity out to z ∼ 1. In this paper we give an overview of the project including the science goals and multiwavelength coverage before presenting the first data release. We have analysed around 400 h of e-MERLIN data allowing us to create a Data Release 1 (DR1) mosaic of $\sim 0.26\, {\rm deg}^2$ to the full depth. These observations have been supplemented with complementary radio observations from the Karl G. Jansky Very Large Array (VLA) and optical/near infrared observations taken with the Subaru, Canada-France-Hawaii, and Spitzer Telescopes. The main data product is a catalogue of 887 sources detected by the VLA, of which 395 are detected by e-MERLIN and 197 of these are resolved. We have investigated the size, flux, and spectral index properties of these sources finding them compatible with previous studies. Preliminary photometric redshifts, and an assessment of galaxy shapes measured in the radio data, combined with a radio-optical cross-correlation technique probing cosmic shear in a supercluster environment, are presented in companion papers.
PubDate: Thu, 02 Apr 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa709
Issue No: Vol. 495, No. 2 (2020)

• SuperCLASS – II. Photometric redshifts and characteristics of spatially
• Authors: Manning S; Casey C, Hung C, et al.
Pages: 1724 - 1736
Abstract: ABSTRACTWe present optical and near-infrared imaging covering a ∼1.53 deg2 region in the Super-Cluster Assisted Shear Survey (SuperCLASS) field, which aims to make the first robust weak lensing measurement at radio wavelengths. We derive photometric redshifts for ≈176 000 sources down to $i^\prime _{\rm AB}\sim 24$ and present photometric redshifts for 1.4 GHz expanded Multi-Element Radio Linked Interferometer Network (e-MERLIN) and Karl G. Jansky Very Large Array (VLA) detected radio sources found in the central 0.26 deg2. We compile an initial catalogue of 149 radio sources brighter than S1.4 > 75 μJy and find their photometric redshifts span 0 < zphot < 4 with radio luminosities between 1021 and 1025 W Hz−1, with medians of $\langle z \rangle \, =0.55$ and $\langle L_{1.4}\rangle \, =1.9\times 10^{23}$ W Hz−1, respectively. We find 95 per cent of the μJy radio source sample (141/149) have spectral energy distributions (SEDs) best fit by star-forming templates while 5 per cent (8/149) are better fit by active galactic nuclei (AGN). Spectral indices are calculated for sources with radio observations from the VLA and Giant Metrewave Radio Telescope (GMRT) at 325 MHz, with an average spectral slope of α = 0.59 ± 0.04. Using the full photometric redshift catalogue, we construct a density map at the redshift of the known galaxy clusters, z = 0.20 ± 0.08. Four of the five clusters are prominently detected at $\gt 7\, \sigma$ in the density map and we confirm the photometric redshifts are consistent with previously measured spectra from a few galaxies at the cluster centres.
PubDate: Thu, 02 Apr 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa657
Issue No: Vol. 495, No. 2 (2020)

• SuperCLASS – III. Weak lensing from radio and optical observations
in Data Release 1
• Authors: Harrison I; Brown M, Tunbridge B, et al.
Pages: 1737 - 1759
Abstract: ABSTRACTWe describe the first results on weak gravitational lensing from the SuperCLASS survey: the first survey specifically designed to measure the weak lensing effect in radio-wavelength data, both alone and in cross-correlation with optical data. We analyse $1.53 \, \mathrm{deg}^2$ of optical data from the Subaru telescope and $0.26 \, \mathrm{deg}^2$ of radio data from the e-MERLIN and VLA telescopes (the DR1 data set). Using standard methodologies on the optical data only we make a significant (10σ) detection of the weak lensing signal (a shear power spectrum) due to the massive supercluster of galaxies in the targeted region. For the radio data we develop a new method to measure the shapes of galaxies from the interferometric data, and we construct a simulation pipeline to validate this method. We then apply this analysis to our radio observations, treating the e-MERLIN and VLA data independently. We achieve source densities of $0.5 \,$ arcmin−2 in the VLA data and $0.06 \,$ arcmin−2 in the e-MERLIN data, numbers which prove too small to allow a detection of a weak lensing signal in either the radio data alone or in cross-correlation with the optical data. Finally, we show preliminary results from a visibility-plane combination of the data from e-MERLIN and VLA which will be used for the forthcoming full SuperCLASS data release. This approach to data combination is expected to enhance both the number density of weak lensing sources available, and the fidelity with which their shapes can be measured.
PubDate: Thu, 02 Apr 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa696
Issue No: Vol. 495, No. 2 (2020)

• Cosmic evolution of molecular gas mass density from an empirical
relationship between L1.4 GHz and L′CO
• Authors: Orellana-González G; Ibar E, Leiton R, et al.
Pages: 1760 - 1770
Abstract: ABSTRACTHistorically, GHz radio emission has been used extensively to characterize the star-formation activity in galaxies. In this work, we look for empirical relationships amongst the radio luminosity, the infrared luminosity, and the CO-based molecular gas mass. We assemble a sample of 278 nearby galaxies with measurements of radio continuum and total infrared emission, and the 12CO J = 1–0 emission line. We find a correlation between the radio continuum and the CO emission line (with a scatter of 0.36 dex), in a large sample of different kinds of galaxies. Making use of this correlation, we explore the evolution of the molecular gas mass function and the cosmological molecular gas mass density in six redshift bins up to z = 1.5. These results agree with previous semi-analytic predictions and direct measurements: the cosmic molecular gas density increases up to z = 1.5. In addition, we find a single plane across five orders of magnitude for the explored luminosities, with a scatter of 0.27 dex. These correlations are sufficiently robust to be used for samples where no CO measurements exist.
PubDate: Wed, 27 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1171
Issue No: Vol. 495, No. 2 (2020)

• HIR4: cosmology from a simulated neutral hydrogen full sky using Horizon
Run 4
• Authors: Asorey J; Parkinson D, Shi F, et al.
Pages: 1788 - 1806
Abstract: ABSTRACTThe distribution of cosmological neutral hydrogen will provide a new window into the large-scale structure of the Universe with the next generation of radio telescopes and surveys. The observation of this material, through 21 cm line emission, will be confused by foreground emission in the same frequencies. Even after these foregrounds are removed, the reconstructed map may not exactly match the original cosmological signal, which will introduce systematic errors and offset into the measured correlations. In this paper, we simulate future surveys of neutral hydrogen using the Horizon Run 4 (HR4) cosmological N-body simulation. We generate H i intensity maps from the HR4 halo catalogue, and combine with foreground radio emission maps from the Global Sky Model, to create accurate simulations over the entire sky. We simulate the H i sky for the frequency range 700–800 MHz, matching the sensitivity of the Tianlai pathfinder. We test the accuracy of the fastICA, PCA, and log-polynomial fitting foreground removal methods to recover the input cosmological angular power spectrum and measure the parameters. We show the effect of survey noise levels and beam sizes on the recovered the cosmological constraints. We find that while the reconstruction removes power from the cosmological 21 cm distribution on large scales, we can correct for this and recover the input parameters in the noise-free case. However, the effect of noise and beam size of the Tianlai pathfinder prevents accurate recovery of the cosmological parameters when using only intensity mapping information.
PubDate: Tue, 05 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1191
Issue No: Vol. 495, No. 2 (2020)

• Differences and similarities of stellar populations in LAEs and LBGs at z
∼ 3.4−6.8
• Authors: Arrabal Haro P; Rodríguez Espinosa J, Muñoz-Tuñón C, et al.
Pages: 1807 - 1824
Abstract: ABSTRACTLyman alpha emitters (LAEs) and Lyman break galaxies (LBGs) represent the most common groups of star-forming galaxies at high z, and the differences between their inherent stellar populations (SPs) are a key factor in understanding early galaxy formation and evolution. We have run a set of SP burst-like models for a sample of 1558 sources at 3.4 < z < 6.8 from the Survey for High-z Absorption Red and Dead Sources (SHARDS) over the GOODS-N field. This work focuses on the differences between the three different observational subfamilies of our sample: LAE–LBGs, no-Ly α LBGs, and pure LAEs. Single and double SP synthetic spectra were used to model the spectral energy distributions, adopting a Bayesian information criterion to analyze under which situations a second SP is required. We find that the sources are well modelled using a single SP in $\sim 79{{\ \rm per\ cent}}$ of the cases. The best models suggest that pure LAEs are typically young low-mass galaxies ($t\sim 26^{+41}_{-25}$ Myr; $M_{\mathrm{star}}\sim 5.6^{+12.0}_{-5.5}\times 10^{8}\ M_{\odot }$), undergoing one of their first bursts of star formation. On the other hand, no-Ly α LBGs require older SPs (t ∼ 71 ± 12 Myr), and they are substantially more massive (Mstar ∼ 3.5 ± 1.1 × 109 M⊙). LAE–LBGs appear as the subgroup that more frequently needs the addition of a second SP, representing an old and massive galaxy caught in a strong recent star-forming episode. The relative number of sources found from each subfamily at each z supports an evolutionary scenario from pure LAEs and single SP LAE–LBGs to more massive LBGs. Stellar mass functions are also derived, finding an increase of M* with cosmic time and a possible steepening of the low-mass slope from z ∼ 6 to z ∼ 5 with no significant change to z ∼ 4. Additionally, we have derived the SFR–Mstar relation, finding an $\mathrm{SFR}\propto M_{\mathrm{star}}^{\beta }$ behaviour with negligible evolution from z ∼ 4 to z ∼ 6.
PubDate: Wed, 06 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1196
Issue No: Vol. 495, No. 2 (2020)

• The impact of AGN feedback on the 1D power spectra from the Ly α forest
using the Horizon-AGN suite of simulations
• Authors: Chabanier S; Bournaud F, Dubois Y, et al.
Pages: 1825 - 1840
Abstract: ABSTRACTThe Lyman-α forest is a powerful probe for cosmology, but it is also strongly impacted by galaxy evolution and baryonic processes such as active galactic nucleus (AGN) feedback, which can redistribute mass and energy on large scales. We constrain the signatures of AGN feedback on the 1D power spectrum of the Lyman-α forest using a series of eight hydro-cosmological simulations performed with the adaptive mesh refinement code ramses. This series starts from the Horizon-AGN simulation and varies the subgrid parameters for AGN feeding, feedback, and stochasticity. These simulations cover the whole plausible range of feedback and feeding parameters according to the resulting galaxy properties. AGNs globally suppress the Lyman-α power at all scales. On large scales, the energy injection and ionization dominate over the supply of gas mass from AGN-driven galactic winds, thus suppressing power. On small scales, faster cooling of denser gas mitigates the suppression. This effect increases with decreasing redshift. We provide lower and upper limits of this signature at nine redshifts between z = 4.25 and 2.0, making it possible to account for it at post-processing stage in future work given that running simulations without AGN feedback can save considerable amounts of computing resources. Ignoring AGN feedback in cosmological inference analyses leads to strong biases with 2 per cent shift on σ8 and 1 per cent shift on ns, which represents twice the standards deviation of the current constraints on ns.
PubDate: Thu, 07 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1242
Issue No: Vol. 495, No. 2 (2020)

• An astrophysically motivated ranking criterion for low-latency
electromagnetic follow-up of gravitational wave events
• Authors: Artale M; Bouffanais Y, Mapelli M, et al.
Pages: 1841 - 1852
Abstract: ABSTRACTWe investigate the properties of the host galaxies of compact binary mergers across cosmic time. To this end, we combine population synthesis simulations together with galaxy catalogues from the hydrodynamical cosmological simulation eagle to derive the properties of the host galaxies of binary neutron star (BNS), black hole-neutron star (BHNS), and binary black hole (BBH) mergers. Within this framework, we derive the host galaxy probability, i.e. the probability that a galaxy hosts a compact binary coalescence as a function of its stellar mass, star formation rate, Ks magnitude, and B magnitude. This quantity is particularly important for low-latency searches of gravitational wave (GW) sources as it provides a way to rank galaxies lying inside the credible region in the sky of a given GW detection, hence reducing the number of viable host candidates. Furthermore, even if no electromagnetic counterpart is detected, the proposed ranking criterion can still be used to classify the galaxies contained in the error box. Our results show that massive galaxies (or equivalently galaxies with a high luminosity in Ks band) have a higher probability of hosting BNS, BHNS, and BBH mergers. We provide the probabilities in a suitable format to be implemented in future low-latency searches.
PubDate: Thu, 07 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1252
Issue No: Vol. 495, No. 2 (2020)

• An obscured AGN population hidden in the VIPERS galaxies: identification
through spectral energy distribution decomposition
• Authors: Pouliasis E; Mountrichas G, Georgantopoulos I, et al.
Pages: 1853 - 1873
Abstract: ABSTRACTThe detection of X-ray emission constitutes a reliable and efficient tool for the selection of active galactic nuclei (AGNs), although it may be biased against the most heavily absorbed AGNs. Simple mid-infrared (IR) broad-band selection criteria identify a large number of luminous and absorbed AGNs, yet again host contamination could lead to non-uniform and incomplete samples. Spectral energy distribution (SED) decomposition is able to decouple the emission from the AGN versus that from star-forming regions, revealing weaker AGN components. We aim to identify the obscured AGN population in the VIMOS Public Extragalactic Redshift Survey in the Canada–France–Hawaii Telescope Legacy Survey W1 field through SED modelling. We construct SEDs for 6860 sources and identify 160 AGNs at a high confidence level using a Bayesian approach. Using optical spectroscopy, we confirm the nature of ∼85 per cent of the AGNs. Our AGN sample is highly complete (∼92 per cent) compared to mid-IR colour-selected AGNs, including a significant number of galaxy-dominated systems with lower luminosities. In addition to the lack of X-ray emission (80 per cent), the SED fitting results suggest that the majority of the sources are obscured. We use a number of diagnostic criteria in the optical, IR, and X-ray regimes to verify these results. Interestingly, only 35 per cent of the most luminous mid-IR-selected AGNs have X-ray counterparts suggesting strong absorption. Our work emphasizes the importance of using SED decomposition techniques to select a population of type II AGNs, which may remain undetected by either X-ray or IR colour surveys.
PubDate: Thu, 07 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1263
Issue No: Vol. 495, No. 2 (2020)

• Probing the AGN unification model at redshift z ∼ 3 with MUSE
observations of giant Ly α nebulae
• Authors: den Brok J; Cantalupo S, Mackenzie R, et al.
Pages: 1874 - 1887
Abstract: ABSTRACTA prediction of the classic active galactic nucleus (AGN) unification model is the presence of ionization cones with different orientations depending on the AGN type. Confirmations of this model exist for present times, but it is less clear in the early Universe. Here, we use the morphology of giant Ly α nebulae around AGNs at redshift z ∼ 3 to probe AGN emission and therefore the validity of the AGN unification model at this redshift. We compare the spatial morphology of 19 nebulae previously found around type I AGNs with a new sample of four Ly α nebulae detected around type II AGNs. Using two independent techniques, we find that nebulae around type II AGNs are more asymmetric than around type I, at least at radial distances r > 30 physical kpc (pkpc) from the ionizing source. We conclude that the type I and type II AGNs in our sample show evidence of different surrounding ionizing geometries. This suggests that the classical AGN unification model is also valid for high-redshift sources. Finally, we discuss how the lack of asymmetry in the inner parts (r ≲ 30 pkpc) and the associated high values of the He ii to Ly α ratios in these regions could indicate additional sources of (hard) ionizing radiation originating within or in proximity of the AGN host galaxies. This work demonstrates that the morphologies of giant Ly α nebulae can be used to understand and study the geometry of high-redshift AGNs on circumnuclear scales and it lays the foundation for future studies using much larger statistical samples.
PubDate: Fri, 08 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1269
Issue No: Vol. 495, No. 2 (2020)

• The pulsation properties of λ bootis stars I. the southern TESS
sample
• Authors: Murphy S; Paunzen E, Bedding T, et al.
Pages: 1888 - 1912
Abstract: ABSTRACTWe analyse TESS light curves for 70 southern λ Boo stars to identify binaries and to determine which of them pulsate as δ Scuti stars. We find two heartbeat stars and two eclipsing binaries among the sample. We calculate that 81 per cent of λ Boo stars pulsate as δ Sct variables, which is about twice that of normal stars over the same parameter space. We determine the temperatures and luminosities of the λ Boo stars from photometry and Gaia DR2 parallaxes. A subset of 40 λ Boo stars have 2-min TESS data, reliable temperatures and luminosities, and δ Sct pulsation. We use Petersen diagrams (period ratios), échelle diagrams, and the period–luminosity relation to identify the fundamental mode in 20 of those 40 stars and conclude that a further 8 stars are not pulsating in this mode. For the remaining 12, the fundamental mode cannot be unambiguously identified. Further mode identification is possible for 12 of the fundamental mode pulsators that have regular sequences of pulsation overtones in their échelle diagrams. We use stellar evolution models to determine statistically that the λ Boo stars are only superficially metal weak. Simple pulsation models also better fit the observations at a metallicity of Z = 0.01 than at Z = 0.001. The TESS observations reveal the great potential of asteroseismology on λ Boo stars, for determining precise stellar ages and shedding light on the origin(s) of the λ Boo phenomenon.
PubDate: Fri, 08 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1271
Issue No: Vol. 495, No. 2 (2020)

• Is the gap in the DS Tau disc hiding a planet'
• Authors: Veronesi B; Ragusa E, Lodato G, et al.
Pages: 1913 - 1926
Abstract: ABSTRACTRecent millimetre-wavelength surveys performed with the Atacama Large Millimeter Array (ALMA) have revealed protoplanetary discs characterized by rings and gaps. A possible explanation for the origin of such rings is the tidal interaction with an unseen planetary companion. The protoplanetary disc around DS Tau shows a wide gap in the ALMA observation at 1.3 mm. We construct a hydrodynamical model for the dust continuum observed by ALMA assuming the observed gap is carved by a planet between one and five Jupiter masses. We fit the shape of the radial intensity profile along the disc major axis varying the planet mass, the dust disc mass, and the evolution time of the system. The best-fitting model is obtained for a planet with $M_{\rm p}=3.5\, \mathrm{ M}_{\rm Jup}$ and a disc with $M_{\rm dust}= 9.6\,\times \,10^{-5}\, \mathrm{ M}_{\odot }$. Starting from this result, we also compute the expected signature of the planet in the gas kinematics, as traced by CO emission. We find that such a signature (in the form of a ‘kink’ in the channel maps) could be observed by ALMA with a velocity resolution between $0.2-0.5\, \rm {kms}^{-1}$ and a beam size between 30 and 50 mas.
PubDate: Sat, 09 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1278
Issue No: Vol. 495, No. 2 (2020)

• Microlensed radio emission from exoplanets
• Authors: Shiohira Y; Terada Y, Mukuno D, et al.
Pages: 1934 - 1942
Abstract: ABSTRACTIn this paper, we investigate the detectability of radio emission from exoplanets, especially hot Jupiters, which are magnified by gravitational microlensing. Because hot Jupiters have orbital periods much shorter than the characteristic time-scale of microlensing, the magnification curve has a unique wavy feature depending on the orbital parameters. This feature is useful to identify radio emission from exoplanets and, in addition to magnification, makes it easier to detect exoplanets directly. We also estimate the expected event rate red of the detectable level of microlensed planetary radio emissions, assuming the Low Frequency Array and the first phase of the Square Kilometre Array.
PubDate: Tue, 12 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1294
Issue No: Vol. 495, No. 2 (2020)

• No significant correlation between radial velocity planet presence and
debris disc properties
• Authors: Yelverton B; Kennedy G, Su K.
Pages: 1943 - 1957
Abstract: ABSTRACTWe investigate whether the tentative correlation between planets and debris discs which has been previously identified can be confirmed at high significance. We compile a sample of 201 stars with known planets and existing far-infrared observations. The sample is larger than those studied previously since we include targets from an unpublished Herschel survey of planet hosts. We use spectral energy distribution modelling to characterize Kuiper belt analogue debris discs within the sample, then compare the properties of the discs against a control sample of 294 stars without known planets. Survival analysis suggests that there is a significant (p ∼ 0.002) difference between the disc fractional luminosity distributions of the two samples. However, this is largely a result of the fact that the control sample contains a higher proportion of close binaries and of later-type stars; both of these factors are known to reduce disc detection rates. Considering only Sun-like stars without close binary companions in each sample greatly reduces the significance of the difference (p ∼ 0.3). We also find no evidence for a difference in the disc fractional luminosities of stars hosting planets more or less massive than Saturn (p ∼ 0.9). Finally, we find that the planet hosts have cooler discs than the control stars, but this is likely a detection bias, since the warmest discs in the control sample are also the faintest, and would thus be undetectable around the more distant planet hosts. Considering only discs in each sample that could have been detected around a typical planet host, we find p ∼ 0.07 for the temperatures.
PubDate: Wed, 13 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1316
Issue No: Vol. 495, No. 2 (2020)

• SDSS-IV MaNGA: The kinematic-morphology of galaxies on the mass versus
star-formation relation in different environments
• Authors: Wang B; Cappellari M, Peng Y, et al.
Pages: 1958 - 1977
Abstract: ABSTRACTWe study the link between the kinematic-morphology of galaxies, as inferred from integral-field stellar kinematics, and their relation between mass and star formation rate. Our sample consists of ∼3200 galaxies with integral-field spectroscopic data from the MaNGA survey (Mapping Nearby Galaxies at Apache Point Observatory) with available determinations of their effective stellar angular momentum within the half-light radius $\lambda _{R_e}$. We find that for star-forming galaxies, namely along the star formation main sequence (SFMS), the $\lambda _{R_e}$ values remain large and almost unchanged over about two orders of magnitude in stellar mass, with the exception of the lowest masses $\mathcal {M}_{\star }\lesssim 2\times 10^{9} \, \mathcal {M}_{\odot }$, where $\lambda _{R_e}$ slightly decreases. The SFMS is dominated by spiral galaxies with small bulges. Below the SFMS, but above the characteristic stellar mass $\mathcal {M}_{\rm crit}\approx 2\times 10^{11} \, \mathcal {M}_{\odot }$, there is a sharp decrease in $\lambda _{R_e}$ with decreasing star formation rate (SFR): massive galaxies well below the SFMS are mainly slow-rotator early-type galaxies, namely genuinely spheroidal galaxies without discs. Below the SFMS and below $\mathcal {M}_{\rm crit}$ the decrease of $\lambda _{R_e}$ with decreasing SFR becomes modest or nearly absent: low-mass galaxies well below the SFMS, are fast-rotator early-type galaxies, and contain fast-rotating stellar discs like their star-forming counterparts. We also find a small but clear environmental dependence for the massive galaxies: in the mass range $10^{10.9}\!-\!10^{11.5} \, \mathcal {M}_{\odot }$, galaxies in rich groups or denser regions or classified as central galaxies have lower values of $\lambda _{R_e}$. While no environmental dependence is found for galaxies of lower mass. We discuss how the above results can be understood as due to the different star formation and mass assembly histories of galaxies with varying mass.
PubDate: Thu, 14 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1325
Issue No: Vol. 495, No. 2 (2020)

• On the origin of the bimodal rotational velocity distribution in stellar
clusters: rotation on the pre-main sequence
• Authors: Bastian N; Kamann S, Amard L, et al.
Pages: 1978 - 1983
Abstract: ABSTRACTWe address the origin of the observed bimodal rotational distribution of stars in massive young and intermediate age stellar clusters. This bimodality is seen as split main sequences at young ages and also has been recently directly observed in the Vsini distribution of stars within massive young and intermediate age clusters. Previous models have invoked binary interactions as the origin of this bimodality, although these models are unable to reproduce all of the observational constraints on the problem. Here, we suggest that such a bimodal rotational distribution is set-up early within a cluster’s life, i.e. within the first few Myr. Observations show that the period distribution of low-mass ($\lesssim\! 2 \, \mathrm{M}_\odot$) pre-main-sequence (PMS) stars is bimodal in many young open clusters, and we present a series of models to show that if such a bimodality exists for stars on the PMS that it is expected to manifest as a bimodal rotational velocity (at fixed mass/luminosity) on the main sequence for stars with masses in excess of ∼1.5 M⊙. Such a bimodal period distribution of PMS stars may be caused by whether stars have lost (rapid rotators) or been able to retain (slow rotators) their circumstellar discs throughout their PMS lifetimes. We conclude with a series of predictions for observables based on our model.
PubDate: Sat, 16 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1332
Issue No: Vol. 495, No. 2 (2020)

• Systematically asymmetric: a comparison of H i profile asymmetries in
real and simulated galaxies
• Authors: Deg N; Blyth S, Hank N, et al.
Pages: 1984 - 2001
Abstract: ABSTRACTWe examine different measures of asymmetry for galaxy H i velocity profiles. We introduce the channel-by-channel asymmetry and the velocity-of-equality statistics to quantify profile asymmetries. Using a sample of simulated galaxies, we examine how these and the standard lopsidedness morphometric statistic depend on a variety of observational effects, including the viewing angle and inclination. We find that our newly introduced channel-by-channel asymmetry is less sensitive to the effects of viewing angle and inclination than other morphometrics. Applying our statistics to the WHISP (Westerbork H i survey of Irregular and SPiral galaxies) H i galaxy sample, we also find that the channel-by-channel asymmetry is a better indicator of visually classified asymmetric profiles. In addition, we find that the lopsidedness–velocity of equality space can be used to identify profiles with deep central dips without visual inspection.
PubDate: Mon, 18 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1368
Issue No: Vol. 495, No. 2 (2020)

• Probing compact dark matter with gravitational wave fringes detected by
the Einstein Telescope
• Authors: Liao K; Tian S, Ding X.
Pages: 2002 - 2006
Abstract: ABSTRACTUnlike the electromagnetic radiation from astrophysical objects, gravitational waves (GWs) from binary star mergers have much longer wavelengths and are coherent. For ground-based GW detectors, when the lens object between the source and the Earth has mass ∼1−105 M⊙, the diffraction effect should be considered since the chirping wavelengths are comparable to the scale of the barrier (its Schwarzschild radius). The waveform will thus be distorted as the fringes. In this work, we show that signals from the third-generation GW detectors like the Einstein Telescope (ET) would be a smoking gun for probing the nature of compact dark matter (CDM) or primordial black holes. Detection of the lensing effects becomes harder when the lens mass is smaller. ET is more sensitive than LIGO, the constraint is available for CDM mass >5 M⊙ while LIGO can only detect the mass >100 M⊙. For a null search of the fringes, one-year observation of ET can constrain the CDM density fraction to ∼10−2 to 10−5 in the mass range MCDM = 10−100 M⊙.
PubDate: Wed, 20 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1388
Issue No: Vol. 495, No. 2 (2020)

• Revising the merger scenario of the galaxy cluster Abell 1644: a new gas
poor structure discovered by weak gravitational lensing
• Authors: Monteiro-Oliveira R; Doubrawa L, Machado R, et al.
Pages: 2007 - 2021
Abstract: ABSTRACTThe galaxy cluster Abell 1644 ($\bar{z}=0.047$) is known for its remarkable spiral-like X-ray emission. It was previously identified as a bimodal system, comprising the subclusters, A1644S and A1644N, each one centred on a giant elliptical galaxy. In this work, we present a comprehensive study of this system, including new weak lensing and dynamical data and analysis plus a tailor-made hydrodynamical simulation. The lensing and galaxy density maps showed a structure in the North that could not be seen on the X-ray images. We, therefore, rename the previously known northern halo as A1644N1 and the new one as A1644N2. Our lensing data suggest that those have fairly similar masses: $M_{200}^{\rm N1}=0.90_{-0.85}^{+0.45} \times 10^{14}$ and $M_{200}^{\rm N2}=0.76_{-0.75}^{+0.37} \times 10^{14}$ M⊙, whereas the southern structure is the main one: $M_{200}^{\rm S}=1.90_{-1.28}^{+0.89}\times 10^{14}$ M⊙. Based on the simulations, fed by the observational data, we propose a scenario where the remarkable X-ray characteristics in the system are the result of a collision between A1644S and A1644N2 that happened ∼1.6 Gyr ago. Currently, those systems should be heading to a new encounter, after reaching their maximum separation.
PubDate: Mon, 18 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1218
Issue No: Vol. 495, No. 2 (2020)

• Simulations of gas sloshing induced by a newly discovered gas poor
substructure in galaxy cluster Abell 1644
• Authors: Doubrawa L; Machado R, Laganá T, et al.
Pages: 2022 - 2034
Abstract: ABSTRACTCollision events lead to peculiar morphologies in the intracluster gas of galaxies clusters. That seems to be the case of Abell 1644, a nearby galaxy cluster, composed of three main structures: the southern cluster that exhibits a spiral-like morphology, A1644S; the northern cluster seen in X-ray observations, A1644N1; and the recently discovered substructure, A1644N2. By means of N-body hydrodynamical simulations, we attempt to reconstruct the dynamical history of this system. These simulations resulted in two specific scenarios: (i) The collision between A1644S and A1644N2. Our best model has an inclination between the merger plane and the plane of the sky of 30°, and reaches the best morphology 1.6 Gyr after the pericentric passage. At this instant A1644N2 is gas poor, becoming nearly undetectable in X-ray emission. This model shows a good agreement with observations; (ii) The collision between A1644S and A1644N1. This approach did not give rise to results as satisfactory as the first scenario, due to great disturbances in density and mismatching temperature maps. As a complementary study, we perform a three-cluster simulation using as base the best-fitting model to reproduce the current state of A1644 with the three main structures. This scenario presented a good agreement to the global morphology of the observations. Thus, we find that the more likely scenario is a collision between A1644S and the newly discovered A1644N2, where A1644N1 may be present as long as it does not greatly interfere in the formation of the spiral feature.
PubDate: Mon, 18 May 2020 00:00:00 GMT
DOI: 10.1093/mnras/staa1051
Issue No: Vol. 495, No. 2 (2020)

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