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Secure confirmation that a gravitational wave (GW) has been gravitationally lensed would bring together these two pillars of General Relativity for the first time. This breakthrough is challenging for many reasons, including: GW sky localization uncertainties dwarf the angular scale of gravitational lensing, the mass and structure of gravitational lenses is diverse, the mass function of stellar remnant compact objects is not yet well constrained, and GW detectors do not operate continuously. We introduce a new approach that is agnostic to the mass and structure of the lenses, compare the efficiency of different methods for lensed GW discovery, and explore detection of lensed kilonova counterparts as a direct method for localising candidates. Our main conclusions are: (1) lensed neutron star mergers (NS-NS) are magnified into the "mass gap" between NS and black holes, therefore selecting candidates from public GW alerts with high mass gap probability is efficient, (2) the rate of detectable lensed NS-NS will approach one per year in the mid-2020s, (3) the arrival time difference between lensed NS-NS images is $1\,\rm sec\lesssim\Delta t\lesssim1\,year$, and thus well-matched to the operations of GW detectors and optical telescopes, (4) lensed kilonova counterparts are faint at peak (e.g.\ $r_{\rm AB}\simeq24-26$ in the mid-2020s), fade quickly ($d, Comment: Accepted by MNRAS. 20 pages, 10 figures

The presence of charged dust grains is known to have a profound impact on the physical evolution of the multiphase interstellar medium (ISM). Despite its importance, this process is still poorly explored in numerical simulations due to its complex physics and the tight dependence on the environment. Here we introduce a novel implementation of grain charging in the cosmological radiative transfer code CRASH. We first benchmark the code predictions on a series of idealized dusty HII regions created by a single star, in order to assess the impact of grain properties on the resulting spatial distribution of charges. Second, we perform a realistic radiative transfer simulation of a star forming region extracted from a dusty galaxy evolving in the Epoch of Reionization. We find that $\sim 13$ % of the total dust mass gets negatively charged, mainly silicate and graphite grains of radius micron. A complex spatial distribution of grain charges is also found, primarily depending on the exposure to stellar radiation and strongly varying along different lines of sight, as a result of radiative transfer effects. We finally assess the impact of grain properties (both chemical composition and size) on the resulting charge distribution. The new implementation described here will open up a wide range of possible studies investigating the physical evolution of the dusty ISM, nowadays accessible to observations of high and low redshift galaxies., Comment: MNRAS in press

We present a machine learning model to classify active galactic nuclei (AGNs) and galaxies (AGN-galaxy classifier) and a model to identify type 1 (optically unabsorbed) and type 2 (optically absorbed) AGN (type 1/2 classifier). We test tree-based algorithms, using training samples built from the X-ray Multi-Mirror Mission–Newton (XMM–Newton) catalogue and the Sloan Digital Sky Survey (SDSS), with labels derived from the SDSS survey. The performance was tested making use of simulations and of cross-validation techniques. With a set of features including spectroscopic redshifts and X-ray parameters connected to source properties (e.g. fluxes and extension), as well as features related to X-ray instrumental conditions, the precision and recall for AGN identification are 94 and 93 per cent, while the type 1/2 classifier has a precision of 74 per cent and a recall of 80 per cent for type 2 AGNs. The performance obtained with photometric redshifts is very similar to that achieved with spectroscopic redshifts in both test cases, while there is a decrease in performance when excluding redshifts. Our machine learning model trained on X-ray features can accurately identify AGN in extragalactic surveys. The type 1/2 classifier has a valuable performance for type 2 AGNs, but its ability to generalize without redshifts is hampered by the limited census of absorbed AGN at high redshift., FJC acknowledges financial support from the Spanish Ministry MCIU under project RTI2018-096686-B-C21 (MCIU/AEI/FEDER/UE), cofunded by FEDER funds and from the Agencia Estatal de Investigación, Unidad de Excelencia María de Maeztu, ref. MDM-2017- 0765. Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions.

In this work, we use the constrained Gaussian realization technique to study the early growth of supermassive black holes (SMBHs) in cosmological hydrodynamic simulations, exploring its relationship with features of the initial density peaks on large scales, ~1 Mpc/h. Our constrained simulations of volume (20 Mpc/h)^3 successfully reconstruct the large-scale structure as well as the black hole growth for the hosts of the rare 10^9 Msun SMBHs found in the BlueTides simulation at z~7. We run a set of simulations with constrained initial conditions by imposing a 5 \sigma_0(R_G) peak on scale of R_G = 1 Mpc/h varying different peak features, such as the shape and compactness as well as the tidal field surrounding the peak. We find that initial density peaks with high compactness and low tidal field induce the most rapid BH growth at early epochs. This is because compact density peaks with a more spherical large scale matter distribution lead to the formation of high density gas clumps in the centers of halos, and thus boost early BH accretion. Moreover, such initially compact density peaks in low tidal field regions also lead to a more compact BH host galaxy morphology. This can explain the tight correlation between BH growth and host galaxy compactness seen in observations., Comment: matches MNRAS accepted version

In this paper, we investigate the properties of binary neutron stars (BNSs) and their mergers by combining population synthesis models for binary stellar evolution (BSE) with cosmological galaxy formation and evolution models. We obtain constraints on BSE model parameters by using the observed Galactic BNSs and local BNS merger rate density ($R_0$) inferred from Gravitational Wave (GW) observations, and consequently estimate the host galaxy distributions of BNS mergers. We find that the Galactic BNS observations imply efficient energy depletion in the common envelope (CE) phase, a bimodal kick velocity distribution, and low mass ejection during the secondary supernova explosion. However, the inferred $R_0$ does not necessarily require an extremely high CE ejection efficiency and low kick velocities, different from the previous claims, mainly because the latest inferred $R_0$ is narrowed to a lower value ($320_{-240}^{+490}\,{\rm Gpc^{-3}\,yr^{-1}}$). The BNS merger rate density resulting from the preferred model can be described by $R(z)\sim R_0(1+z)^{\zeta}$ at low redshift ($z\lesssim0.5$), with $R_0\sim316$-$784\,{\rm Gpc^{-3}\,yr^{-1}}$ and $\zeta\sim1.34$-$2.03$, respectively. Our results also show that $R_{0}$ and $\zeta$ depend on settings of BSE model parameters, and thus accurate estimates of these parameters by future GW detections will put strong constraints on BSE models. We further estimate that the fractions of BNS mergers hosted in spiral and elliptical galaxies at $z\sim0$ are $\sim81$%-$84$% and $\sim16$%-$19$%, respectively. The BNS merger rate per galaxy can be well determined by the host galaxy stellar mass, star formation rate, and metallicity, which provides a guidance in search for most probable candidates of BNS host galaxies., Comment: 32 pages, 17 figures, accepted for publication in MNRAS

The characteristic mass that sets the peak of the stellar initial mass function (IMF) is closely linked to the thermodynamic behaviour of interstellar gas, which controls how gas fragments as it collapses under gravity. As the Universe has grown in metal abundance over cosmic time, this thermodynamic behaviour has evolved from a primordial regime dominated by the competition between compressional heating and molecular hydrogen cooling to a modern regime where the dominant process in dense gas is protostellar radiation feedback, transmitted to the gas by dust-gas collisions. In this paper we map out the primordial-to-modern transition by constructing a model for the thermodynamics of collapsing, dusty gas clouds at a wide range of metallicities. We show the transition from the primordial regime to the modern regime begins at metallicity $Z\sim 10^{-4} \rm{Z_\odot}$, passes through an intermediate stage where metal line cooling is dominant at $Z \sim 10^{-3}\,\rm{Z_{\odot}}$, and then transitions to the modern dust- and feedback-dominated regime at $Z\sim 10^{-2} \rm{Z_\odot}$. In low pressure environments like the Milky Way, this transition is accompanied by a dramatic change in the characteristic stellar mass, from $\sim 50\,\rm{M_\odot}$ at $Z \sim 10^{-6}\,\rm{Z_{\odot}}$ to $\sim 0.3\,\rm{M_\odot}$ once radiation feedback begins to dominate, which marks the appearance of the modern bottom-heavy Milky Way IMF. In the high pressure environments typical of massive elliptical galaxies, the characteristic mass for the modern, dust-dominated regime falls to $\sim 0.1\,\rm{M_{\odot}}$, thus providing an explanation for the more bottom-heavy IMF observed in these galaxies. We conclude that metallicity is a key driver of variations in the characteristic stellar mass, and by extension, the IMF., 26 pages (main result in figures 7 and 8). MNRAS in press

We estimate the 3D density profile of the Galactic dark matter (DM) halo within $r \lesssim 30$ kpc from the Galactic centre by using the astrometric data for halo RR Lyrae stars from Gaia DR2. We model both the stellar halo distribution function and the Galactic potential, fully taking into account the survey selection function, the observational errors, and the missing line-of-sight velocity data for RR Lyrae stars. With a Bayesian MCMC method, we infer the model parameters, including the density flattening of the DM halo $q$, which is assumed to be constant as a function of radius. We find that 99\% of the posterior distribution of $q$ is located at $q>0.963$, which strongly disfavours a flattened DM halo. We cannot draw any conclusions as to whether the Galactic DM halo at $r \lesssim 30$ kpc is prolate, because we restrict ourselves to axisymmetric oblate halo models with $q\leq1$. Our result is inconsistent with predictions from cosmological hydrodynamical simulations that advocate more oblate ($\langle{q}\rangle \sim0.8 \pm 0.15$) DM halos within $\sim 15\%$ of the virial radius for Milky-Way-sized galaxies. An alternative possibility, based on our validation tests with a cosmological simulation, is that the true value $q$ of the Galactic halo could be consistent with cosmological simulations but that disequilibrium in the Milky Way potential is inflating our measurement of $q$ by 0.1-0.2. As a by-product of our analysis, our model constrains the DM density in the Solar neighbourhood to be $��_{\mathrm{DM},\odot} = (9.01^{+0.18}_{-0.20})\times10^{-3}M_\odot \mathrm{pc}^{-3} = 0.342^{+0.007}_{-0.007}$ $\;\mathrm{GeV} \mathrm{cm}^{-3}$., MNRAS submitted. 15 pages (plus Appendix 7 pages). 6 figures (plus 10 figures in Appendix). Comments welcome

We characterize the selection cuts and clustering properties of a magnitude-limited sample of bright galaxies that is part of the Bright Galaxy Survey (BGS) of the Dark Energy Spectroscopic Instrument (DESI) using the ninth data release of the Legacy Imaging Surveys (DR9). We describe changes in the DR9 selection compared to the DR8 one and we also compare the DR9 selection in three distinct regions: BASS/MzLS in the north Galactic Cap (NGC), DECaLS in the NGC, and DECaLS in the south Galactic Cap (SGC). We investigate the systematics associated with the selection and assess its completeness by matching the BGS targets with the Galaxy and Mass Assembly (GAMA) survey. We measure the angular clustering for the overall bright sample (rmag ≤ 19.5) and as function of apparent magnitude and colour. This enables to determine the clustering strength r0 and slope γ by fitting a power-law model that can be used to generate accurate mock catalogues for this tracer. We use a counts-in-cells technique to explore higher order statistics and cross-correlations with external spectroscopic data sets in order to check the evolution of the clustering with redshift and the redshift distribution of the BGS targets using clustering redshifts. While this work validates the properties of the BGS bright targets, the final target selection pipeline and clustering properties of the entire DESI BGS will be fully characterized and validated with the spectroscopic data of Survey Validation. © 2021 The Author(s)., PZ, OR-M, SC, PN, and CB acknowledge support from the Science Technology Facilities Council through ST/P000541/1 andST/T000244/1. OR-M is supported by the Mexican National Council of Science and Technology (CONACyT) through grant No. 297228/440775 and funding from the European Union’s Horizon 2020 Research and Innovation Programme under the Marie Sklodowska-Curie grant agreement No 734374. JM gratefully acknowledges support from the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DESC0020086 and from the National Science Foundation under grant AST-1616414. Authors want to thank the GAMA collaboration for early access to GAMA DR4 data for this work. Some of the results in this paper have been derived using the healpy and HEALPIX package. We acknowledge the usage of the HyperLeda database (http://leda.univ-lyon1.fr).This work also made extensive use of the NASA Astrophysics Data System and of the astro-ph preprint archive at arXiv.org. This work used the DiRAC@Durham facility managed by the Institute for Computational Cosmology on behalf of the STFC DiRAC HPC Facility (www.dirac.ac.uk). The equipment was funded by BEIS capital funding via STFC capital grants ST/K00042X/1, ST/P002293/1, and ST/R002371/1, Durham University and STFC operations grant ST/R000832/1. DiRAC is part of the National e-Infrastructure. This research used resources of the National Energy Research Scientific Computing Center (NERSC). NERSC is a U.S. Department of Energy Office of Science User Facility operated under Contract No. DE-AC02-05CH11231. This research is supported by the Director, Office of Science, Office of High Energy Physics of the U.S. Department of Energy under Contract No. DE-AC02-05CH1123, and by the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility under the same contract; additional support for DESI is provided by the U.S. National Science Foundation, Division of Astronomical Sciences under Contract No. AST-0950945 to the NSF’s National Optical-Infrared Astronomy Research Laboratory; the Science and Technologies Facilities Council of the United Kingdom; the Gordon and Betty Moore Foundation; the Heising-Simons Foundation; the French Alternative Energies and Atomic Energy Commission (CEA); the National Council of Science and Technology of Mexico; the Ministry of Economy of Spain, and by the DESI Member Institutions. The authors are honored to be permitted to conduct astronomical research on Iolkam Du’ag (Kitt Peak), a mountain with particular significance to the Tohono O’odham Nation., With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.

The locations of Ly-$\alpha$ emitting galaxies (LAEs) at the end of the Epoch of Reionisation (EoR) are expected to correlate with regions of ionised hydrogen, traced by the redshifted 21~cm hyperfine line. Mapping the neutral hydrogen around regions with detected and localised LAEs offers an avenue to constrain the brightness temperature of the Universe within the EoR by providing an expectation for the spatial distribution of the gas, thereby providing prior information unavailable to power spectrum measurements. We use a test set of 12 hours of observations from the Murchison Widefield Array (MWA) in extended array configuration, to constrain the neutral hydrogen signature of 58 LAEs, detected with the Subaru Hypersuprime Cam in the \textit{Silverrush} survey, centred on $z$=6.58. We assume that detectable emitters reside in the centre of ionised HII bubbles during the end of reionization, and predict the redshifted neutral hydrogen signal corresponding to the remaining neutral regions using a set of different ionised bubble radii. A prewhitening matched filter detector is introduced to assess detectability. We demonstrate the ability to detect, or place limits upon, the amplitude of brightness temperature fluctuations, and the characteristic HII bubble size. With our limited data, we constrain the brightness temperature of neutral hydrogen to $\Delta{\rm T}_B, Comment: 9 pages, 6 figures, accepted for publication in MNRAS

With the advent of large spectroscopic surveys the amount of high quality chemo-dynamical data in the Milky Way (MW) increased tremendously. Accurately and correctly capturing and explaining the detailed features in the high-quality observational data is notoriously difficult for state-of-the-art numerical models. In order to keep up with the quantity and quality of observational datasets, improved prescriptions for galactic chemical evolution need to be incorporated into the simulations. Here we present a new, flexible, time resolved chemical enrichment model for cosmological simulations. Our model allows to easily change a number of stellar physics parameters such as the shape of the initial mass function (IMF), stellar lifetimes, chemical yields or SN Ia delay times. We implement our model into the Gasoline2 code and perform a series of cosmological simulations varying a number of key parameters, foremost evaluating different stellar yield sets for massive stars from the literature. We find that total metallicity, total iron abundance and gas phase oxygen abundance are robust predictions from different yield sets and in agreement with observational relations. On the other hand, individual element abundances, especially $\alpha$-elements show significant differences across different yield sets and none of our models can simultaneously match constraints on the dwarf and MW mass scale. This offers a unique way of observationally constraining model parameters. For MW mass galaxies we find for most yield tables tested in this work a bimodality in the $[\alpha$/Fe] vs. [Fe/H] plane of rather low intrinsic scatter potentially in tension with the observed abundance scatter., Comment: main text 19 pages and 11 figures, 4 pages of appendix, 23 pages total, python code and data at https://github.com/TobiBu/chemical_enrichment.git. submitted to MNRAS, comments very welcome

Roman Space Telescope will survey about 17 million emission-line galaxies over a range of redshifts. Its main targets are Hα emission-line galaxies at low redshifts (z < 2) and [O iii] emission-line galaxies at high redshifts (z > 2). The Roman Space Telescope will estimate the redshift of these galaxies with single-line identification. This suggests that other emission-line galaxies may be misidentified as the main targets. In particular, it is hard to distinguish between the H β and [O iii] lines as the two lines are close in wavelength and hence the photometric information may not be sufficient to separate them reliably. Misidentifying H β emitter as [O iii] emitter will cause a shift in the inferred radial position of the galaxy by approximately 90 Mpc h−1. This length-scale is similar to the Baryon Acoustic Oscillation (BAO) scale and could shift and broaden the BAO peak, possibly introduce errors in determining the BAO peak position. We qualitatively describe the effect of this new systematic and further quantify it with a light-cone simulation with emission-line galaxies. Our results show a systematic shift in the recovered isotropic BAO positions that depends on the percentage of interlopers (percentage of ${\rm H}\,\beta$) in the sample. The systematic shift can be as large as $0.1{-}0.3\,\mathrm{ per}\,\mathrm{ cent} \, {\rm x}\, {{\%}}{\rm H}\,\beta$ for analysis performed at redshifts z = 1.3−1.9.

The circumgalactic medium (CGM) encodes signatures of the galaxy-formation process, including the interaction of galactic outflows driven by stellar and supermassive black hole (SMBH) feedback with the gaseous halo. Moving beyond spherically symmetric radial profiles, we study the \textit{angular} dependence of CGM properties around $z=0$ massive galaxies in the IllustrisTNG simulations. We characterize the angular signal of density, temperature, and metallicity of the CGM as a function of galaxy stellar mass, halo mass, distance, and SMBH mass, via stacking. TNG predicts that the CGM is anisotropic in its thermodynamical properties and chemical content over a large mass range, $M_*\sim10^{10-11.5}M_\odot$. Along the minor axis directions, gas density is diluted, whereas temperature and metallicity are enhanced. These feedback-induced anisotropies in the CGM have a magnitude of $0.1-0.3$ dex, extend out to the halo virial radius, and peak at Milky Way-like masses, $M_*\sim10^{10.8}M_\odot$. In TNG, this mass scale corresponds to the onset of efficient SMBH feedback and the production of strong outflows. By comparing the anisotropic signals predicted by TNG versus other simulations -- Illustris and EAGLE -- we find that each simulation produces distinct signatures and mass dependencies, implying that this phenomenon is sensitive to the underlying physical models. Finally, we explore X-ray emission as an observable of this CGM anistropy, finding that future X-ray observations, including the eROSITA all-sky survey, will be able to detect and characterize this signal, particularly in terms of an angular modulation of the X-ray hardness., Comment: 19 pages, 9 figures + Appendix. Accepted for publication in MNRAS

When the light from a distant object passes very near to a foreground galaxy or cluster, gravitational lensing can cause it to appear as multiple images on the sky. If the source is variable, it can be used to constrain the cosmic expansion rate and dark energy models. Achieving these cosmological goals requires many lensed transients with precise time delay measurements. Lensed supernovae (SN) are attractive for this purpose because they have relatively simple photometric behavior, with well-understood light curve shapes and colours $-$ in contrast to the stochastic variation of quasars. Here we report the discovery of a multiply-imaged supernova, AT2016jka ("SN Requiem"). It appeared in an evolved galaxy at $z=1.95$, gravitationally lensed by a foreground galaxy cluster. It is likely a Type Ia supernova $-$ the explosion of a low-mass stellar remnant, whose light curve can be used to measure cosmic distances. In archival Hubble Space Telescope imaging, three lensed images of the supernova are detected with relative time delays of $, Comment: Accepted for publication in a peer-reviewed journal. Main text = 6 pages, 3 figures, 1 table; Full document = 28 pages, 12 figures with Methods, Supplemental Info and references. v2: reformatted; minor corrections in SI

Gravitational waves (GWs) may be magnified or de-magnified due to lensing. This phenomenon will bias the distance estimation based on the matched filtering technique. Via the multi-sphere ray-tracing technique, we study the GW magnification effect and selection effect with particular attention to the stellar-mass binary black holes (BBHs). We find that, for the observed luminosity distance $\lesssim 3~\mathrm{Gpc}$, which is the aLIGO/Virgo observational horizon limit, the average magnification keeps as unity, namely unbiased estimation, with the relative distance uncertainty $\sigma(\hat{d})/\hat{d}\simeq0.5\%\sim1\%$. Beyond this observational horizon, the estimation bias can not be ignored, and with the scatters $\sigma(\hat{d})/\hat{d} = 1\%\sim 15\%$. Furthermore, we forecast these numbers for Einstein Telescope. We find that the average magnification keeps closely as unity for the observed luminosity distance $\lesssim 90~\mathrm{Gpc}$. The luminosity distance estimation error due to lensing for Einstein Telescope is about $\sigma(\hat{d})/\hat{d} \simeq 10\%$ for the luminosity distance $\gtrsim 25~\mathrm{Gpc}$. Unlike the aLIGO/Virgo case, this sizable error is not due to the selection effect. It purely comes from the unavoidably accumulated lensing magnification. Moreover, we investigated the effects of the orientation angle and the BH mass distribution models. We found that the results are strongly dependent on these two components., Comment: 9 pages, 9 figures, published in MNRAS

We present a detailed study of the shapes and alignments of different galaxy cluster components using hydrodynamical simulations. We compute shape parameters from the Dark Matter (DM) distribution, the galaxy members and the intra-cluster light (ICL). We assess how well the DM cluster shape can be constrained by means of the identified galaxy member positions and the ICL. Further, we address the dilution factor introduced when estimating the cluster elongation using weak-lensing stacking techniques, which arises due to the misalignment between the total surface mass distribution and the distribution of luminous tracers. The dilution is computed considering the alignment between the DM and the Brightest Cluster Galaxy, the galaxy members and the ICL. Our study shows that distributions of galaxy members and ICL are less spherical than the DM component, although both are well aligned with the semi-major axis of the later. We find that the distribution of galaxy members hosted in more concentrated subhalos is more elongated than the distribution of the DM. Moreover, these galaxies are better aligned with the dark matter component compared to the distribution of galaxies hosted in less concentrated subhalos. We conclude that the positions of galaxy members can be used as suitable tracers to estimate the cluster surface density orientation, even when a low number of members is considered. Our results provide useful information for interpreting the constraints on the shapes of galaxy clusters in observational studies., Comment: Submitted MNRAS. 12 pages, 7 figures (+ appendix)

Upcoming galaxy surveys and 21-cm experiments targeting high redshifts $z\gtrsim 6$ are highly complementary probes of galaxy formation and reionization. However, in order to expedite the large volume simulations relevant for 21-cm observations, many models of galaxies within reionization codes are entirely subgrid and/or rely on halo abundances only. In this work, we explore the extent to which resolving and modeling individual galaxy formation histories affects predictions both for the galaxy populations detectable by upcoming surveys and the signatures of reionization accessible to upcoming 21-cm experiments. We find that a common approach, in which galaxy luminosity is assumed to be a function of halo mass only, is biased with respect to models in which galaxy properties are evolved through time via semi-analytic modeling and thus reflective of the diversity of assembly histories that naturally arise in $N$-body simulations. The diversity of galaxy formation histories also results in scenarios in which the brightest galaxies do \textit{not} always reside in the centers of large ionized regions, as there are often relatively low-mass halos undergoing dramatic, but short-term, growth. This has clear implications for attempts to detect or validate the 21-cm background via cross correlation. Finally, we show that a hybrid approach -- in which only halos hosting galaxies bright enough to be detected in surveys are modeled in detail, with the rest modeled as an unresolved field of halos with abundance related to large-scale overdensity -- is a viable way to generate large-volume `simulations` well-suited to wide-area surveys and current-generation 21-cm experiments targeting relatively large $k \lesssim 1 \ h \ \text{Mpc}^{-1}$ scales., Comment: 17 pages, 14 figures, accepted for publication in MNRAS

The high redshift Lyman-alpha forest, in particular the Gunn-Peterson trough, is the most unambiguous signature of the neutral to ionized transition of the intergalactic medium (IGM) taking place during the Epoch of Reionization (EoR). Recent studies, e.g. Kulkarni et al. (2019a) and Keating et al. (2019), showed that reproducing the observed Lyman-alpha opacities after overlap required a non-monotonous evolution of cosmic emissivity: rising, peaking at z=6, and then decreasing onwards to z=4. Such an evolution is puzzling considering galaxy build-up and the cosmic star formation rate are still continously on the rise at these epochs. Here, we use new RAMSES-CUDATON simulations to show that such a peaked evolution may occur naturally in a fully coupled radiation-hydrodynamical framework. In our fiducial run, cosmic emissivity at z>6 is dominated by a low mass (M$_{\rm DM}, 10 pages, 6 figures, accepted for publication in MNRAS

Understanding the impact of halo properties beyond halo mass on the clustering of galaxies (namely galaxy assembly bias) remains a challenge for contemporary models of galaxy clustering. We explore the use of machine learning to predict the halo occupations and recover galaxy clustering and assembly bias in a semi-analytic galaxy formation model. For stellar-mass selected samples, we train a Random Forest algorithm on the number of central and satellite galaxies in each dark matter halo. With the predicted occupations, we create mock galaxy catalogues and measure the clustering and assembly bias. Using a range of halo and environment properties, we find that the machine learning predictions of the occupancy variations with secondary properties, galaxy clustering and assembly bias are all in excellent agreement with those of our target galaxy formation model. Internal halo properties are most important for the central galaxies prediction, while environment plays a critical role for the satellites. Our machine learning models are all provided in a usable format. We demonstrate that machine learning is a powerful tool for modelling the galaxy-halo connection, and can be used to create realistic mock galaxy catalogues which accurately recover the expected occupancy variations, galaxy clustering and galaxy assembly bias, imperative for cosmological analyses of upcoming surveys., 21 pages, 17 figures, submitted to MNRAS

In this work, we use the {\sc astraeus} (seminumerical rAdiative tranSfer coupling of galaxy formaTion and Reionization in N-body dArk mattEr simUlationS) framework which couples galaxy formation and reionization in the first billion years. Exploring a number of models for reionization feedback and the escape fraction of ionizing radiation from the galactic environment ($f_\mathrm{esc}$), we quantify how the contribution of star-forming galaxies {(with halo masses $M_h>10^{8.2}$M$_\odot$)} to reionization depends on the radiative feedback model, $f_\mathrm{esc}$, and the environmental over-density. Our key findings are: (i) for constant $f_\mathrm{esc}$ models, intermediate-mass galaxies (with halo masses of $M_h\simeq10^{9-11}$M$_\odot$ and absolute UV magnitudes of $M_{UV} \sim -15$ to $-20$) in intermediate-density regions drive reionization; (ii) scenarios where $f_\mathrm{esc}$ increases with decreasing halo mass shift the galaxy population driving reionization to lower-mass galaxies ($M_h\lesssim10^{9.5}$M$_\odot$) with lower luminosities ($M_{UV} \gtrsim-16$) and over-densities; (iii) reionization imprints its topology on the ionizing emissivity of low-mass galaxies ($M_h\lesssim10^{9}$M$_\odot$) through radiative feedback. Low-mass galaxies experience a stronger suppression of star formation by radiative feedback and show lower ionizing emissivities in over-dense regions; (iv) a change in $f_\mathrm{esc}$ with galaxy properties has the largest impact on the sources of reionization and their detectability, with the radiative feedback strength and environmental over-density playing a sub-dominant role; (v) JWST-surveys (with a limiting magnitude of $M_{UV} = -16$) will be able to detect the galaxies providing $\sim 60-70\%$ ($\sim 10\%$) of reionization photons at $z=7$ for constant $f_\mathrm{esc}$ models (scenarios where $f_\mathrm{esc}$ increases with decreasing halo mass)., 14 pages, 13 figures, accepted for publication in MNRAS

We present results from a resolved stellar population search for dwarf satellite galaxies of six nearby (D $, Comment: 14 pages, 10 figures. Accepted to MNRAS. Comments welcomed

The diffuse extragalactic background light (EBL) is formed by ultraviolet (UV), optical, and infrared (IR) photons mainly produced by star formation processes over the history of the Universe, and contains essential information about galaxy evolution and cosmology. Here, we present a new determination of the evolving EBL spectral energy distribution using a novel approach purely based on galaxy data aiming to reduce current uncertainties on the higher redshifts and IR intensities. Our calculations use multiwavelength observations from the UV to the far-IR of a sample of approximately 150,000 galaxies detected up to $z\sim 6$ in the five fields of the Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey (CANDELS) from the Hubble Space Telescope. This is one of the most comprehensive and deepest multi-wavelength galaxy datasets ever obtained. These unprecedented resources allow us to derive the overall EBL evolution up to $z\sim 6$ and its uncertainties. Our results agree with cosmic observables estimated from galaxy surveys and $\gamma$-ray attenuation such as monochromatic luminosity densities, including those in the far-IR, and star formation rate densities, also at the highest redshits. Optical depths from our EBL approximation, which will be robust at high redshifts and for $\gamma$ rays up to tens of TeV, will be reported in a companion paper., Comment: 17 pages, 13 figures, 4 tables; accepted for publication in MNRAS on August 6, 2021. Online material available at https://www.ucm.es/blazars/ebl

One of the main predictions of excursion set theory is that the clustering of dark matter haloes only depends on halo mass. However, it has been long established that the clustering of haloes also depends on other properties, including formation time, concentration, and spin; this effect is commonly known as halo assembly bias. We use a suite of gravity-only simulations to study the dependence of halo assembly bias on cosmology; these simulations cover cosmological parameters spanning 10$\sigma$ around state-of-the-art best-fitting values, including standard extensions of the $\Lambda$CDM paradigm such as neutrino mass and dynamical dark energy. We find that the strength of halo assembly bias presents variations smaller than 0.05 dex across all cosmologies studied for concentration and spin selected haloes, letting us conclude that the dependence of halo assembly bias upon cosmology is negligible. We then study the dependence of galaxy assembly bias (i.e. the manifestation of halo assembly bias in galaxy clustering) on cosmology using subhalo abundance matching. We find that galaxy assembly bias also presents very small dependence upon cosmology ($\sim$ 2$\%$-4$\%$ of the total clustering); on the other hand, we find that the dependence of this signal on the galaxy formation parameters of our galaxy model is much stronger. Taken together, these results let us conclude that the dependence of halo and galaxy assembly bias on cosmology is practically negligible., Comment: 11 pages, 8 figures. Submitted to MNRAS, comments welcome

How does the environment affect active galactic nucleus (AGN) activity? We investigated this question in an extinction-free way, by selecting 1120 infrared galaxies in the $AKARI$ North Ecliptic Pole Wide field at redshift $z$ $\leq$ 1.2. A unique feature of the $AKARI$ satellite is its continuous 9-band infrared (IR) filter coverage, providing us with an unprecedentedly large sample of IR spectral energy distributions (SEDs) of galaxies. By taking advantage of this, for the first time, we explored the AGN activity derived from SED modelling as a function of redshift, luminosity, and environment. We quantified AGN activity in two ways: AGN contribution fraction (ratio of AGN luminosity to the total IR luminosity), and AGN number fraction (ratio of number of AGNs to the total galaxy sample). We found that galaxy environment (normalised local density) does not greatly affect either definitions of AGN activity of our IRG/LIRG samples (log ${\rm L}_{\rm TIR}$ $\leq$ 12). However, we found a different behavior for ULIRGs (log ${\rm L}_{\rm TIR}$ $>$ 12). At our highest redshift bin (0.7 $\lesssim$ z $\lesssim$ 1.2), AGN activity increases with denser environments, but at the intermediate redshift bin (0.3 $\lesssim$ z $\lesssim$ 0.7), the opposite is observed. These results may hint at a different physical mechanism for ULIRGs. The trends are not statistically significant (p $\geq$ 0.060 at the intermediate redshift bin, and p $\geq$ 0.139 at the highest redshift bin). Possible different behavior of ULIRGs is a key direction to explore further with future space missions (e.g., $JWST$, $Euclid$, $SPHEREx$)., Accepted for publication in MNRAS. A summary video is available at https://www.youtube.com/watch?v=7Y_a0kJkLI4&ab_channel=NthuCosmology

We present strong-lensing analyses of three galaxy clusters, RXJ2129.4+0009 (z=0.235), MS0451.6-0305 (z=0.55), and MACSJ2129.4-0741 (z=0.589), using the powerful combination of Hubble Space Telescope (HST) multi-band observations, and Multi-Unit Spectroscopic Explorer (MUSE) spectroscopy. In RXJ2129, we newly spectroscopically confirm 15 cluster members. Our resulting mass model uses 8 multiple image systems as we include a galaxy-galaxy lensing system North-East of the cluster, and is composed of 71 halos including one dark matter cluster-scale halo and 2 galaxy-scale halos optimized individually. For MS0451, we report the spectroscopic identification of 2 new systems of multiple images in the Northern region, and 112 cluster members. Our mass model uses 16 multiple image systems, and 146 halos, including 2 large-scale halos, and 7 galaxy-scale halos independently optimized. For MACSJ2129, we report the spectroscopic identification of one new multiple image system at z=4.41, and newly measure spectroscopic redshifts for 4 cluster members. Our mass model uses 14 multiple image systems, and is composed of 151 halos, including 2 large-scale halos and 4 galaxy-scale halos independently optimized. Our best models have rms of 0.29'', 0.6'', 0.74'' in the image plane for RXJ2129, MS0451, and MACSJ2129 respectively. This analysis presents a detailed comparison with the existing literature showing excellent agreements, and discuss specific studies of lensed galaxies, e.g. a group of submilimeter galaxies at z=2.9 in MS0451, and a bright z=2.1472 red singly imaged galaxy in MACSJ2129., 25 pages, 10 figures, 13 tables, accepted in MNRAS

Galaxy clusters provide an excellent probe in various research fields in astrophysics and cosmology. However, the number of galaxy clusters detected so far in the $AKARI$ North Ecliptic Pole (NEP) field is limited. In this work, we provide galaxy cluster candidates in the $AKARI$ NEP field with the minimum requisites based only on coordinates and photometric redshift (photo-$z$) of galaxies. We used galaxies detected in 5 optical bands ($g$, $r$, $i$, $z$, and $Y$) by the Subaru Hyper Suprime-Cam (HSC), assisted with $u$-band from Canada-France-Hawaii Telescope (CFHT) MegaPrime/MegaCam, and IRAC1 and IRAC2 bands from the $Spitzer$ space telescope for photo-$z$ estimation. We calculated the local density around every galaxy using the 10$^{th}$-nearest neighbourhood. Cluster candidates were determined by applying the friends-of-friends algorithm to over-densities. 88 cluster candidates containing 4390 member galaxies below redshift 1.1 in 5.4 deg$^2$ have been detected. The reliability of our method was examined through false detection tests, redshift uncertainty tests, and applications on the COSMOS data, giving false detection rates of 0.01 to 0.05 and recovery rate of 0.9 at high richness. 3 X-ray clusters previously observed by $ROSAT$ and $Chandra$ were recovered. The cluster galaxies show higher stellar mass and lower star formation rate (SFR) compared to the field galaxies in two-sample Z-tests. These cluster candidates are useful for environmental studies of galaxy evolution and future astronomical surveys in the NEP, where $AKARI$ has performed unique 9-band mid-infrared photometry for tens of thousands of galaxies., Comment: 19 pages, 16 figures, has been accepted for publication in MNRAS

Core formation and runaway core collapse in models with self-interacting dark matter (SIDM) significantly alter the central density profiles of collapsed halos. Using a forward modeling inference framework with simulated datasets, we demonstrate that flux ratios in quadruple image strong gravitational lenses can detect the unique structural properties of SIDM halos, and statistically constrain the amplitude and velocity dependence of the interaction cross section in halos with masses between $10^6 - 10^{10} M_{\odot}$. Measurements on these scales probe self-interactions at velocities below $30 \ \rm{km} \ \rm{s^{-1}}$, a relatively unexplored regime of parameter space, complimenting constraints at higher velocities from galaxies and clusters. We cast constraints on the amplitude and velocity dependence of the interaction cross section in terms of $\sigma_{20}$, the cross section amplitude at $20 \ \rm{km} \ \rm{s^{-1}}$. With 50 lenses, a sample size available in the near future, and flux ratios measured from spatially compact mid-IR emission around the background quasar, we forecast $\sigma_{20} < 11-23 \ \rm{cm^2} \rm{g^{-1}}$ at $95 \%$ CI, depending on the amplitude of the subhalo mass function, and assuming cold dark matter (CDM). Alternatively, if $\sigma_{20} = 19.2 \ \rm{cm^2}\rm{g^{-1}}$ we can rule out CDM with a likelihood ratio of 20:1, assuming an amplitude of the subhalo mass function that results from doubly-efficient tidal disruption in the Milky Way relative to massive elliptical galaxies. These results demonstrate that strong lensing of compact, unresolved sources can constrain SIDM structure on sub-galactic scales across cosmological distances, and the evolution of SIDM density profiles over several Gyr of cosmic time., Comment: matches version accepted to MNRAS

It has long been argued that the radial distribution of globular clusters (GCs) in the Fornax dwarf galaxy requires its dark matter halo to have a core of size $\sim 1$ kpc. We revisit this argument by investigating analogues of Fornax formed in E-MOSAICS, a cosmological hydrodynamical simulation that self-consistently follows the formation and evolution of GCs in the EAGLE galaxy formation model. In EAGLE, Fornax-mass haloes are cuspy and well described by the Navarro-Frenk-White profile. We post-process the E-MOSAICS to account for GC orbital decay by dynamical friction, which is not included in the original model. Dynamical friction causes 33 per cent of GCs with masses $M_{\rm GC}\geq4\times10^4 {~\rm M_\odot}$ to sink to the centre of their host where they are tidally disrupted. Fornax has a total of five GCs, an exceptionally large number compared to other galaxies of similar stellar mass. In the simulations, we find that only 3 per cent of the Fornax analogues have five or more GCs, while 30 per cent have only one and 35 per cent have none. We find that GC systems in satellites are more centrally concentrated than in field dwarfs, and that those formed in situ (45 per cent) are more concentrated than those that were accreted. The survival probability of a GC increases rapidly with the radial distance at which it formed ($r_{\rm init}$): it is 37 per cent for GCs with $r_{\rm init} \leq 1$ kpc and 92 per cent for GCs with $r_{\rm init} \geq 1$ kpc. The present-day radial distribution of GCs in E-MOSAICS turns out to be indistinguishable from that in Fornax, demonstrating that, contrary to claims in the literature, the presence of five GCs in the central kiloparsec of Fornax does not exclude a cuspy DM halo., 15 pages, 13 figures. submitted to MNRAS, comments welcome!

We report the discovery of an intrinsically faint, quintuply-imaged, dusty galaxy MACS0600-z6 at a redshift $z=$6.07 viewed through the cluster MACSJ0600.1-2008 ($z$=0.46). A $\simeq4\sigma$ dust detection is seen at 1.2mm as part of the ALMA Lensing Cluster Survey (ALCS), an on-going ALMA Large program, and the redshift is secured via [C II] 158 $\mu$m emission described in a companion paper. In addition, spectroscopic follow-up with GMOS/Gemini-North shows a break in the galaxy's spectrum, consistent with the Lyman break at that redshift. We use a detailed mass model of the cluster and infer a magnification $\mu\gtrsim$30 for the most magnified image of this galaxy, which provides an unprecedented opportunity to probe the physical properties of a sub-luminous galaxy at the end of cosmic reionisation. Based on the spectral energy distribution, we infer lensing-corrected stellar and dust masses of $\rm{2.9^{+11.5}_{-2.3}\times10^9}$ and $\rm{4.8^{+4.5}_{-3.4}\times10^6}$ $\rm{M_{\odot}}$ respectively, a star formation rate of $\rm{9.7^{+22.0}_{-6.6} M_{\odot} yr^{-1}}$, an intrinsic size of $\rm{0.54^{+0.26}_{-0.14}}$ kpc, and a luminosity-weighted age of 200$\pm$100 Myr. Strikingly, the dust production rate in this relatively young galaxy appears to be larger than that observed for equivalent, lower redshift sources. We discuss if this implies that early supernovae are more efficient dust producers and the consequences for using dust mass as a probe of earlier star formation., Comment: submitted to MNRAS, revised version after including referee's comments

We present a novel scenario for the growth of dust grains in galaxies at high-redshift ($z\sim 6$). In our model, the mechanical feedback from massive star clusters evolving within high-density pre-enriched media allows to pile-up a large amount of matter into massive supershells. If the gas metallicity ($\geq$ Z$_{\odot}$), number density ($\geq 10^6$ cm$^{-3}$) and dust-to-gas mass ratio ($\sim 1/150 \times Z$) within the supershell are sufficiently large, such supershells may become optically thick to the starlight emerging from their host star clusters and even to radiation from the Cosmic Microwave Background (CMB). Based on semi-analytic models, we argue that this mechanism, occurring in the case of massive ($\geq 10^7$ M$_{\odot}$) molecular clouds hosting $\geq 10^6$ M$_{\odot}$ star clusters, allows a large mass of gas and dust to acquire a temperature below that of the CMB, whereupon dust grain growth may occur with ease. In galaxies with total stellar mass $M_{*}$, grain growth within supershells may increase the dust mass by $\sim 10^6$ M$_{\odot}$ $(M_{*}/10^{8}$ M$_{\odot}$)., Comment: 10 pages, 7 figures, accepted for publication by MNRAS

Water megamasers at 22 GHz with a gas disk configuration in galaxies provide the most precise measurements of supermassive black hole masses, as well as independent constraints on the Hubble constant in the nearby universe. The existence of other maser types, such as jet or outflow masers, represents another tracer for AGN science. However, the detection rate of water megamasers in galaxies is extremely low. Over 40 years, only $\sim$ 160 galaxies are found to harbour maser emission, and $\sim$ 30\% of them show features in their maser emission that indicate a disk-like geometry. Therefore, increasing the detection rate of masers is a crucial task to allow expanding on maser studies. We present a comparison of mid-infrared spectroscopic data between a maser galaxy sample and a Seyfert 2 control sample. We find that maser galaxies show significant peculiarities in their mid-infrared spectra: (1) Maser galaxies tend to present stronger silicate absorption at $\tau$ 9.7 $\mu$m than the control sample, (2) PAH 11.3 $\mu$m emission in maser galaxies is much weaker than in the control sample, (3) spectral indices at 20-30 $\mu$m are steeper in maser galaxies than in the control sample and tend to be mid-infrared enhanced population. We conclude that there may be good indicators in mid-infrared and far-infrared which could differentiate maser and non-maser Seyfert 2 galaxies. Upcoming infrared facilities, such as the James Webb Space Telescope, may be able to exploit these and other useful criteria and tracers for water megamaser observations., Comment: 11 pages, 6 figures, 1 appendix; accepted for publication in MNRAS

The use of continuum emission radio galaxies as cosmological tracers of the large-scale structure will soon move into a new phase. Upcoming surveys from the Australian Square Kilometre Array Pathfinder (ASKAP), MeerKAT, and the Square Kilometre Array project (SKA) will survey the entire available sky down to an ~100uJy flux limit, increasing the number of detected extra-galactic radio sources by several orders of magnitude. External data and machine learning algorithms will also enable some low resolution radial selection (photometric redshift binning) of the sample, increasing the cosmological utility of the sample observed. In this paper, we discuss the flux limit required to detect enough galaxies to decrease the shot noise term in the error to be 10% of the total. We show how future surveys of this type will be limited by available technology. The confusion generated by the intrinsic sizes of galaxies may have the consequence that surveys of this type eventually reach a hard flux limit of ~100nJy, as is predicted by the current modelling of AGN sizes by simulations such as the Tiered Radio Extragalactic Continuum Simulation (T-RECS). Finally, when considering the multi-tracer approach, where galaxies are split by type to measure some bias ratio, we find that there are not enough AGN present to achieve a reasonable level of shot noise for this kind of measurement., 10 pages, 8 figures, submitted to the journal

The transmission of Lyman-{\alpha} (Ly{\alpha}) in the spectra of distant quasars depends on the density, temperature, and ionization state of the intergalactic medium (IGM). Therefore, high-redshift (z > 5) Ly{\alpha} forests could be invaluable in studying the late stages of the epoch of reionization (EoR), as well as properties of the sources that drive it. Indeed, high-quality quasar spectra have now firmly established the existence of large-scale opacity fluctuations at z > 5, whose physical origins are still debated. Here we introduce a Bayesian framework capable of constraining the EoR and galaxy properties by forward-modelling the high-z Ly{\alpha} forest. Using priors from galaxy and CMB observations, we demonstrate that the final overlap stages of the EoR (when >95% of the volume was ionized) should occur at z < 5.6, in order to reproduce the large-scale opacity fluctuations seen in forest spectra. However, it is the combination of patchy reionization and the inhomogeneous UV background that produces the longest Gunn-Peterson troughs. Ly{\alpha} forest observations tighten existing constraints on the characteristic ionizing escape fraction of galaxies, with the combined observations suggesting f_{\rm esc} \approx 7^4_3%, and disfavoring a strong evolution with the galaxy's halo (or stellar) mass., Comment: 19 pages, 11 figures, submitted to MNRAS, comments are welcome

Expanding from previous work we present weak lensing measurements for a total sample of 30 distant ($z_\mathrm{median}=0.93$) massive galaxy clusters from the South Pole Telescope Sunyaev-Zel'dovich (SPT-SZ) Survey, measuring galaxy shapes in Hubble Space Telescope (HST) Advanced Camera for Surveys images. We remove cluster members and preferentially select $z\gtrsim 1.4$ background galaxies via $V-I$ colour, employing deep photometry from VLT/FORS2 and Gemini-South/GMOS. We apply revised calibrations for the weak lensing shape measurements and the source redshift distribution to estimate the cluster masses. In combination with earlier Magellan/Megacam results for lower-redshifts clusters we infer refined constraints on the scaling relation between the SZ detection significance and the cluster mass, in particular regarding its redshift evolution. The mass scale inferred from the weak lensing data is lower by a factor $0.76^{+0.10}_{-0.14}$ (at our pivot redshift $z=0.6$) compared to what would be needed to reconcile a flat Planck $\nu\Lambda$CDM cosmology (in which the sum of the neutrino masses is a free parameter) with the observed SPT-SZ cluster counts. In order to sensitively test the level of (dis-)agreement between SPT clusters and Planck, further expanded weak lensing follow-up samples are needed., Comment: 32 pages, 20 figures, 12 tables, matches the version accepted for publication in MNRAS

The dispersion measure (DM) of fast radio bursts (FRBs) provides a unique way to probe ionised baryons in the intergalactic medium (IGM). Cosmological models with different parameters lead to different DM-redshift ($\mathrm{DM}-z$) relations. Additionally, the over/under-dense regions in the IGM and the circumgalactic medium of intervening galaxies lead to scatter around the mean $\mathrm{DM}-z$ relations. We have used the Evolution and Assembly of GaLaxies and their Environments (EAGLE) simulations to measure the mean $\mathrm{DM}-z$ relation and the scatter around it using over one billion lines-of-sight between redshifts $0, Comment: Submitted to MNRAS. 14 pages, 15 figures, Comments Welcome. Data and model will be released upon being accepted

Voids may affect galaxy formation via weakening mass infall or increasing disk sizes, which could potentially play a role in the formation of giant low surface brightness galaxies (LSBGs). If a dark matter halo forms at the potential hill corresponding to a void of the cosmic web, which we denote the 'elaphrocentre' in contrast to a barycentre, then the elaphrocentre should weaken the infall rate to the halo when compared to infall rates towards barycentres. We investigate this hypothesis numerically. We present a complete software pipeline to simulate galaxy formation, starting from a power spectrum of initial perturbations and an N-body simulation through to merger-history-tree based mass infall histories. The pipeline is built from well-established, free-licensed cosmological software packages, and aims at highly portable long-term reproducibility. We find that the elaphrocentric accelerations tending to oppose mass infall are modest. We do not find evidence of location in a void or elaphrocentric position weakening mass infall towards a galaxy. However, we find indirect evidence of voids influencing galaxy formation: while void galaxies are of lower mass compared to galaxies in high density environments, their spin parameters are typically higher. For a fixed mass, the implied disk scale length would be greater. Tangential accelerations in voids are found to be high and might significantly contribute to the higher spin parameters. We find significantly later formation epochs for void galaxies; this should give lower matter densities and may imply lower surface densities of disk galaxies. Thus, void galaxies have higher spin parameters and later formation epochs; both are factors that may increase the probability of forming LSBGs in voids., 16 pages, 16 figures, 4 tables, reproducibility: zenodo.4699702 at https://zenodo.org/record/4699702, git: https://codeberg.org/boud/elaphrocentre ; v3: matches accepted version

We use the {\sc Illustris TNG300} magneto-hydrodynamic simulation, the {\sc SAGE} semi-analytical model, and the subhalo abundance matching technique (SHAM) to examine the diversity in predictions for galaxy assembly bias (i.e. the difference in the large scale clustering of galaxies at a fixed halo mass due to correlations with the assembly history and other properties of host haloes). We consider samples of galaxies selected according to their stellar mass or star formation rate at various redshifts. We find that all models predict an assembly bias signal of different magnitude, redshift evolution, and dependence with selection criteria and number density. To model these non-trivial dependences, we propose an extension to the standard SHAM technique so it can include arbitrary amounts of assembly bias. We do this by preferentially selecting subhaloes with the same internal property but different {\it individual} large-scale bias. We find that with this model, we can successfully reproduce the galaxy assembly bias signal in either {\sc SAGE} or the {\sc TNG}, for all redshifts and galaxy number densities. We anticipate that this model can be used to constrain the level of assembly bias in observations and aid in the creation of more realistic mock galaxy catalogues., Accepted by mnras

We investigate the performance of group finding algorithms that reconstruct galaxy groups from the positional information of tracer galaxies that are observed in redshift surveys carried out with multiplexed spectrographs. We use mock light-cones produced by the L-Galaxies semi-analytic model of galaxy evolution in which the underlying reality is known. We particularly focus on the performance at high redshift, and how this is affected by choices of the mass of the tracer galaxies (largely equivalent to their co-moving number density) and the (assumed random) sampling rate of these tracers. We first however compare two different approaches to group finding as applied at low redshift, and conclude that these are broadly comparable. For simplicity we adopt just one of these, "Friends-of-Friends" (FoF) as the basis for our study at high redshift. We introduce 12 science metrics that are designed to quantify the performance of the group-finder as relevant for a wide range of science investigations with a group catalogue. These metrics examine the quality of the recovered group catalogue, the median halo masses of different richness structures, the scatter in dark matter halo mass and how successful the group-finder classifies singletons, centrals and satellites. We analyze how these metrics vary with the limiting stellar mass and random sampling rate of the tracer galaxies, allowing quantification of the various trade-offs between different possible survey designs. Finally, we look at the impact of these same design parameters on the relative "costs" in observation time of the survey using as an example the potential MOONRISE survey using the MOONS instrument., ERC STFC

We present radio observations of ultraluminous infrared galaxies (ULIRGs) using the Giant Metrewave Radio Telescope (GMRT) and combine them with archival multi-frequency observations to understand whether ULIRGs are the progenitors of the powerful radio loud galaxies in the local Universe. ULIRGs are characterized by large infrared luminosities ($L_{IR}>$10$^{12}$L$\odot$), large dust masses ($\sim10^{8}M_{\odot}$) and vigorous star formation (star formation rates $\sim$10-100 $M_{\odot}~$yr$^{-1}$). Studies show that they represent the end stages of mergers of gas-rich spiral galaxies. Their luminosity can be due to both starburst activity and active galactic nuclei (AGN). We study a sample of 13 ULIRGs that have optically identified AGN characteristics with 1.28~GHz GMRT observations. Our aim is to resolve any core-jet structures or nuclear extensions and hence examine whether the ULIRGs are evolving into radio loud ellipticals. Our deep, low frequency observations show marginal extension for only one source. However, the integrated radio spectra of 9 ULIRGs show characteristics that are similar to that of GPS/CSS/CSO/young radio sources. The estimated spectral ages are 0.4 to 20 Myr and indicate that they are young radio sources and possible progenitors of radio galaxies. Hence, we conclude that although most ULIRGs do not show kpc scale extended radio emission associated with nuclear activity, their radio spectral energy distributions do show signatures of young radio galaxies., 16 pages, 13 figures. Accepted for publication in MNRAS

The line-of-sight velocity dispersion profile of galaxy clusters exhibits a "kink" corresponding to the spatial extent of orbiting galaxies. Because the spatial extent of a cluster is correlated with the amplitude of the velocity dispersion profile, we can utilise this feature as a gravity-calibrated standard ruler. Specifically, the amplitude of the velocity dispersion data allows us to infer the physical cluster size. Consequently, observations of the angular scale of the "kink" in the profile can be translated into a distance measurement to the cluster. Assuming the relation between cluster radius and cluster velocity dispersion can be calibrated from simulations, we forecast that with existing data from the Sloan Digital Sky Survey (SDSS) we will be able to measure the Hubble constant with $3\%$ precision. Implementing our method with data from the Dark Energy Spectroscopic Instrument (DESI) will result in a $1.3\%$ measurement of the Hubble constant. Adding cosmological supernova data improves the uncertainty of the DESI measurement to $0.7\%$., 8 pages, 5 figures, to be submitted to MNRAS

In this paper we present results from a radio-optical study of the galaxy populations of the galaxy clusters Abell 1300 and MACS J1931.8$-$2634, a merger and a relaxed system respectively both located at $z \sim 0.3$, aimed at finding evidence of merger-induced radio emission. Radio observations are taken at 1.28 GHz with the MeerKAT interferometer during its early-stage commissioning phase, and combined with archive optical data. We generated catalogues containing 107 and 162 radio sources in the A$~$1300 and MACS J1931.8--2634 cluster fields respectively, above a 0.2 mJy threshold and within a 30~arcmin radius from the cluster centre (corresponding to 8.1 and 8.8 Mpc respectively). By cross-correlating the radio and optical catalogues, and including spectroscopic information, 9 and 6 sources were found to be cluster members and used to construct the radio luminosity functions respectively for both clusters. The comparison of the radio source catalogues between the two cluster fields leads to a marginal difference, with a $2��$ statistical significance. We derived the radio luminosity function at 1.28 GHz in both clusters, in the power range $22.81 < \rm {log~P_{1.28~GHz}~(W/Hz)} < 25.95$, and obtained that in A 1300 the radio luminosity function averaged over the full radio power interval is only $3.3 \pm 1.9$ times higher than the MACS J1931.8--2634 one, suggesting no statistical difference in their probability to host nuclear radio emission. We conclude that, at least for the two clusters studied here, the role of cluster mergers in affecting the statistical properties of the radio galaxy population is negligible., 18 pages, 8 figures, MNRAS accepted

Motivated by two seminal models proposed to explain the Universe acceleration, this paper is devoted to study a hybrid model which is constructed through a generalized Chaplygin gas with the addition of a bulk viscosity. We call the model a Viscous Generalized Chaplygin Gas (VGCG) and its free parameters are constrained through several cosmological data like the Observational Hubble Parameter, Type Ia Supernovae, Baryon Acoustic Oscillations, Strong Lensing Systems, HII Galaxies and using Joint Bayesian analysis. In addition, we implement a Om-diagnostic to analyze the VGCC dynamics and its difference with the standard cosmological model. The hybrid model shows important differences when compared with the standard cosmological model. Finally, based on our Joint analysis we find that the VGCG could be an interesting candidate to alleviate the well-known Hubble constant tension., Accepted for publication in EPJC

Rosell, A., et al. (DES Collaboration), In this paper, we present and validate the galaxy sample used for the analysis of the baryon acoustic oscillation (BAO) signal in the Dark Energy Survey (DES) Y3 data. The definition is based on a colour and redshift-dependent magnitude cut optimized to select galaxies at redshifts higher than 0.5, while ensuring a high-quality determination. The sample covers ~4100 deg2 to a depth of i = 22.3 (AB) at 10s. It contains 7031 993 galaxies in the redshift range from z = 0.6 to 1.1, with a mean effective redshift of 0.835. Redshifts are estimated with the machine learning algorithm DNF, and are validated using the VIPERS PDR2 sample. We find a mean redshift bias of zbias~0.01 and a mean uncertainty, in units of 1 + z, of σ68~0.03. We evaluate the galaxy population of the sample, showing it is mostly built upon Elliptical to Sbc types. Furthermore, we find a low level of stellar contamination of ≤ 4 per cent. We present the method used to mitigate the effect of spurious clustering coming from observing conditions and other large-scale systematics.We apply it to the BAO sample and calculate weights that are used to get a robust estimate of the galaxy clustering signal. This paper is one of a series dedicated to the analysis of the BAO signal in DES Y3. In the companion papers, we present the galaxy mock catalogues used to calibrate the analysis and the angular diameter distance constraints obtained through the fitting to the BAO scale., The DES data management system is supported by the National Science Foundation under Grant Numbers AST-1138766 and AST-1536171. The DES participants from Spanish institutions are partially supported by MICINN under grants ESP2017-89838,PGC2018-094773, PGC2018-102021, SEV-2016-0588, SEV-2016-0597, and MDM-2015-0509, some of which include ERDF funds from the European Union. IFAE is partially funded by the CERCA program of the Generalitat de Catalunya. Research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Program (FP7/2007-2013) including ERC grant agreements 240672, 291329, and 306478. We acknowledge support from the Brazilian Instituto Nacional de Ciência e Tecnologia (INCT) do e-Universo (CNPq grant 465376/2014-2). ACR acknowledges financial support from the Spanish Ministry of Science, Innovation and Universities (MICIU) under grant AYA2017-84061-P, co-financed by FEDER (European Regional Development Funds) and by the Spanish Space Research Program ‘Participation in the NISP instrument and preparation for the science of EUCLID’ (ESP2017-84272-C2-1-R). SA was supported by the MICUES project, funded by the EU’s H2020 MSCA grant agreement no. 713366 (InterTalentum UAM).

We introduce Z-Sequence, a novel empirical model that utilises photometric measurements of observed galaxies within a specified search radius to estimate the photometric redshift of galaxy clusters. Z-Sequence itself is composed of a machine learning ensemble based on the k-nearest neighbours algorithm. We implement an automated feature selection strategy that iteratively determines appropriate combinations of filters and colours to minimise photometric redshift prediction error. We intend for Z-Sequence to be a standalone technique but it can be combined with cluster finders that do not intrinsically predict redshift, such as our own DEEP-CEE. In this proof-of-concept study we train, fine-tune and test Z-Sequence on publicly available cluster catalogues derived from the Sloan Digital Sky Survey. We determine the photometric redshift prediction error of Z-Sequence via the median value of $|\Delta z|/(1+z)$ (across a photometric redshift range of $0.05 \le \textit{z} \le 0.6$) to be $\sim0.01$ when applying a small search radius. The photometric redshift prediction error for test samples increases by 30-50 per cent when the search radius is enlarged, likely due to line-of-sight interloping galaxies. Eventually, we aim to apply Z-Sequence to upcoming imaging surveys such as the Legacy Survey of Space and Time to provide photometric redshift estimates for large samples of as yet undiscovered and distant clusters., Comment: Accepted to MNRAS on 16th March 2021; pp. 1-21. Supplementary material is included; pp. 22-164

Most of the dark matter (DM) search over the last few decades has focused on WIMPs, but the viable parameter space is quickly shrinking. Asymmetric Dark Matter (ADM) is a WIMP-like DM candidate with slightly smaller masses and no present day annihilation, meaning that stars can capture and build up large quantities. The captured ADM can transport energy through a significant volume of the star. We investigate the effects of spin-dependent ADM energy transport on stellar structure and evolution in stars with $0.9 \leq M_{\star}/\mathrm{M}_{\odot} \leq 5.0$ in varying DM environments. We wrote a MESA module that calculates the capture of DM and the subsequent energy transport within the star. We fix the DM mass to 5 GeV and the cross section to $10^{-37} \mathrm{cm{^2}}$, and study varying environments by scaling the DM capture rate. For stars with radiative cores ($M_{\star} \lesssim 1.3\ \mathrm{M}_{\odot}$), the presence of ADM flattens the temperature and burning profiles in the core and increases MS ($X_c > 10^{-3}$) lifetimes by up to $\sim 20\%$. We find that strict requirements on energy conservation are crucial to the simulation of ADM's effects on these stars. In higher-mass stars, ADM energy transport shuts off core convection, limiting available fuel and shortening MS lifetimes by up to $\sim 40\%$. This may translate to changes in the luminosity and effective temperature of the MS turnoff in population isochrones. The tip of the red giant branch may occur at lower luminosities. The effects are largest in DM environments with high densities and/or low velocity dispersions, making dwarf and early forming galaxies most likely to display the effects., 14 pages, 8 figures, submitted to Monthly Notices of the Royal Astronomical Society

We carry out ``full-physics'' hydrodynamical simulations of galaxy formation in the normal-branch Dvali-Gabadadze-Porrati (nDGP) braneworld model using a new modified version of the {\sc Arepo} code and the IllustrisTNG galaxy formation model. We simulate two nDGP models (N5 and N1) which represent, respectively, weak and moderate departures from GR, in boxes of sizes $62\,h^{-1}{\rm Mpc}$ and $25\,h^{-1}{\rm Mpc}$ using $2\times512^3$ dark matter particles and initial gas cells. This allows us to explore, for the first time, the impact of baryonic physics on galactic scales in braneworld models of modified gravity and to make predictions on the stellar content of dark matter haloes and galaxy evolution through cosmic time in these models. We find significant differences between the GR and nDGP models in the power spectra and correlation functions of gas, stars and dark matter of up to $\sim 25$ per cent on large scales. Similar to their impact in the standard cosmological model ($\Lambda$CDM), baryonic effects can have a significant influence over the clustering of the overall matter distribution, with a sign that depends on scale. Studying the degeneracy between modified gravity and galactic feedback in these models, we find that these two physical effects on matter clustering can be cleanly disentangled, allowing for a method to accurately predict the matter power spectrum with baryonic effects included, without having to run hydrodynamical simulations. Depending on the braneworld model, we find differences compared with GR of up to $\sim15$ per cent in galaxy properties such as the stellar-to-halo-mass ratio, galaxy stellar mass function, gas fraction and star formation rate density. The amplitude of the fifth force is reduced by the presence of baryons in the very inner part of haloes, but this reduction quickly becomes negligible above $\sim0.1$ times the halo radius., Comment: 18 pages, 9 figures, matches with published version

Large-scale sky surveys require companion large volume simulated mock catalogs. To ensure precision cosmology studies are unbiased, the correlations in these mocks between galaxy properties and their large-scale environments must be realistic. Since galaxies are embedded in dark matter halos, an important first step is to include such correlations -- sometimes called assembly bias -- for dark matter halos. However, galaxy properties correlate with smaller scale physics in halos which large simulations struggle to resolve. We describe an algorithm which addresses and largely mitigates this problem. Our algorithm exploits the fact that halo assembly bias is unchanged as long as correlations between halo property $c$ and the intermediate-scale tidal environment $\alpha$ are preserved. Therefore, knowledge of $\alpha$ is sufficient to assign small-scale, otherwise unresolved properties to a halo in a way which preserves its large-scale assembly bias accurately. We demonstrate this explicitly for halo internal properties like formation history (concentration $c_{\rm 200b}$), shape $c/a$, dynamics $c_{v}/a_{v}$, velocity anisotropy $\beta$ and angular momentum (spin $\lambda$). Our algorithm increases a simulation's reach in halo mass and number density by an order of magnitude, with improvements in the bias signal as large as 45% for 30-particle halos, thus significantly reducing the cost of mocks for future weak lensing and redshift space distortion studies., Comment: 13 pages, 10 figures, minor revisions, accepted in MNRAS

Observations suggest that satellite quenching plays a major role in the build-up of passive, low-mass galaxies at late cosmic times. Studies of low-mass satellites, however, are limited by the ability to robustly characterize the local environment and star-formation activity of faint systems. In an effort to overcome the limitations of existing data sets, we utilize deep photometry in Stripe 82 of the Sloan Digital Sky Survey, in conjunction with a neural network classification scheme, to study the suppression of star formation in low-mass satellite galaxies in the local Universe. Using a statistically-driven approach, we are able to push beyond the limits of existing spectroscopic data sets, measuring the satellite quenched fraction down to satellite stellar masses of ${\sim}10^7~{\rm M}_{\odot}$ in group environments (${M}_{\rm{halo}} = 10^{13-14}~h^{-1}~{\rm M}_{\odot}$). At high satellite stellar masses ($\gtrsim 10^{10}~{\rm M}_{\odot}$), our analysis successfully reproduces existing measurements of the quenched fraction based on spectroscopic samples. Pushing to lower masses, we find that the fraction of passive satellites increases, potentially signaling a change in the dominant quenching mechanism at ${M}_{\star} \sim 10^{9}~{\rm M}_{\odot}$. Similar to the results of previous studies of the Local Group, this increase in the quenched fraction at low satellite masses may correspond to an increase in the efficacy of ram-pressure stripping as a quenching mechanism in groups., Comment: Key Figures: 3, 4 and 8; 11 pages; 8 figures; Accepted for publication in MNRAS 2021 February 18. Received 2021 February 15; in original form 2020 December 11

In the local Universe, there is a handful of dwarf compact star-forming galaxies with extremely low oxygen abundances. It has been proposed that they are young, having formed a large fraction of their stellar mass during their last few hundred Myr. However, little is known about the fraction of young stellar populations in more massive galaxies. In a previous article, we analyzed 280 000 SDSS spectra to identify a surprisingly large sample of more massive Very Young Galaxies (VYGs), defined to have formed at least $50\%$ of their stellar mass within the last 1 Gyr. Here, we investigate in detail the properties of a subsample of 207 galaxies that are VYGs according to all three of our spectral models. We compare their properties with those of control sample galaxies (CSGs). We find that VYGs tend to have higher surface brightness and to be more compact, dusty, asymmetric, and clumpy than CSGs. Analysis of a subsample with HI detections reveals that VYGs are more gas-rich than CSGs. VYGs tend to reside more in the inner parts of low-mass groups and are twice as likely to be interacting with a neighbour galaxy than CSGs. On the other hand, VYGs and CSGs have similar gas metallicities and large scale environments (relative to filaments and voids). These results suggest that gas-rich interactions and mergers are the main mechanisms responsible for the recent triggering of star formation in low-redshift VYGs, except for the lowest mass VYGs, where the starbursts may arise from a mixture of mergers and gas infall., 33 pages, 24 figures, to be published in MNRAS

We present improved modelling of the redshift-space distortions of galaxy clustering that arise from peculiar velocities. We create mock galaxy catalogues in the framework of the halo model, using data from the Bolshoi project. These mock galaxy populations are inserted into the haloes with additional degrees of freedom that govern spatial and kinematical biases of the galaxy populations relative to the dark matter. We explore this generalised halo model with an MCMC algorithm, comparing the predictions to data from the Galaxy And Mass Assembly (GAMA) survey, and thus derive one of the first constraints on the detailed kinematic degrees of freedom for satellite galaxies within haloes. With this approach, the distortions of the redshift-space galaxy autocorrelations can be accounted for down to spatial separations close to 10 kpc, opening the prospect of improved RSD measurements of the perturbation growth rate by the inclusion of data from nonlinear scales., Comment: 19 pages, 10 figures, final published version with only minor text changes for clarifications

We present a new statistical analysis of the large-scale stellar mass distribution in the Sloan Digital Sky Survey (data release 7). A set of volume-limited samples shows that the stellar mass of galaxies is concentrated in a range of galaxy luminosities that is very different from the range selected by the usual analysis of galaxy positions. Nevertheless, the two-point correlation function is a power-law with the usual exponent $\gamma=1.71$--$1.82$, which varies with luminosity. The mass concentration property allows us to make a meaningful analysis of the angular distribution of the full flux-limited sample. With this analysis, after suppressing the shot noise, we extend further the scaling range and thus obtain $\gamma=1.83$ and a clustering length \redc{$r_0= 5.8$--$7.0\,h^{-1}$Mpc.} Fractional statistical moments of the coarse-grained stellar mass density exhibit multifractal scaling. Our results support a multifractal model with a transition to homogeneity at about $10\,h^{-1}$Mpc., Comment: 19 pages, 6 figures; new results: shot noise suppression, fractional moments, analysis of VL samples; to be published in Advances in Astronomy