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The Lambda-Cold Dark Matter (LCDM) model agrees with most of the cosmological observations, but has some hindrances from observed data at smaller scales such as galaxies. Recently, Berezhiani and Khoury (2015) proposed a new theory involving interacting superfluid dark matter with three model parameters, which explains galactic dynamics with great accuracy. In the present work, we study the cosmological behaviour of this model in the linear regime of cosmological perturbations. In particular, we compute both analytically and numerically the matter linear growth factor and obtain new bounds for the model parameters which are significantly stronger than previously found. These new constraints come from the fact that structures within the superfluid dark matter framework grow quicker than in LCDM, and quite rapidly when the DM-baryon interactions are strong., Comment: 16 pages, 6 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.

The central regions of cool-core galaxy clusters harbour multiphase gas, with gas temperatures ranging from $10$ $\mathrm{K}$--$10^7$$\mathrm{K}$. Feedback from active galactic nuclei (AGNs) jets prevents the gas from undergoing a catastrophic cooling flow. However, the exact mechanism of this feedback energy input is unknown, mainly due to the lack of velocity measurements of the hot phase gas. However, recent observations have measured the velocity structure functions ($\mathrm{VSF}$s) of the cooler molecular ($\sim10$$\mathrm{K}$) and H$\alpha$ filaments ($\sim10^4$$\mathrm{K}$) and used them to indirectly estimate the motions of the hot phase. In the first part of this study, we conduct high-resolution ($384^3$--$1536^3$ resolution elements) simulations of homogeneous isotropic subsonic turbulence, without radiative cooling. We analyse the second-order velocity structure functions ($\mathrm{VSF}_2$) in these simulations and study the effects of varying spatial resolution, the introduction of magnetic fields, and the effect of projection along the line of sight (LOS) on it. In the second part of the study, we analyse high-resolution ($768^3$ resolution elements) idealised simulations of multiphase turbulence in the intracluster medium (ICM) from Mohapatra et al 2021. We compare the $\mathrm{VSF}_2$ for both the hot ($T\sim10^7$$\mathrm{K}$) and cold ($T\sim10^4$$\mathrm{K}$) phases and find that their amplitude depends on the density contrast between the phases. They have similar scaling with separation, but introducing magnetic fields steepens the $\mathrm{VSF}_2$ of only the cold phase. We also find that projection along the LOS steepens the $\mathrm{VSF}_2$ for the hot phase and mostly flattens it for the cold phase., Comment: 17 pages, 11 figures, simulation movies at this youtube playlist: https://www.youtube.com/watch?v=-_0WIfRL9tI&list=PLuaNgQ1v_KMauk1cTu_ellwe6-pTkABIh. Accepted for publication in MNRAS, comments are welcome. Companion study at arxiv ID 2107.07722

We use the Sherwood-Relics suite of hybrid hydrodynamical and radiative transfer simulations to model the effect of inhomogeneous reionisation on the 1D power spectrum of the \Lya forest transmitted flux at redshifts $4.2\leq z \leq 5$. Relative to models that assume a homogeneous UV background, reionisation suppresses the power spectrum at small scales, $k \sim 0.1\rm\,km^{-1}\,s$ by $\sim 10$ per cent because of spatial variations in the thermal broadening kernel and the divergent peculiar velocity field associated with over-pressurised intergalactic gas. On larger scales, $k4$, $0.006 \rm \,km^{-1}\,s\leq k \leq 0.2 \rm\, km^{-1}\,s$, we find inhomogeneous reionisation does not introduce any significant bias in thermal parameter recovery for the current measurement uncertainties of $\sim 10$ per cent. However, for $5$ per cent uncertainties, $\sim 1\sigma$ shifts between the estimated and true parameters occur., Comment: Accepted by MNRAS (21 November 2021), 20 pages, 11 figures

We present updated cosmological constraints from measurements of the gas mass fractions ($f_{gas}$) of massive, dynamically relaxed galaxy clusters. Our new data set has greater leverage on models of dark energy, thanks to the addition of the Perseus Cluster at low redshifts, two new clusters at redshifts $z>0.97$, and significantly longer observations of four clusters at $0.6, Comment: To be published in MNRAS. See https://github.com/abmantz/fgas-cosmo for code and https://github.com/abmantz/fgas-2021-paper for data presented in figures/tables

Obtaining accurately calibrated redshift distributions of photometric samples is one of the great challenges in photometric surveys like LSST, Euclid, HSC, KiDS, and DES. We present an inference methodology that combines the redshift information from the galaxy photometry with constraints from two-point functions, utilizing cross-correlations with spatially overlapping spectroscopic samples, and illustrate the approach on CosmoDC2 simulations. Our likelihood framework is designed to integrate directly into a typical large-scale structure and weak lensing analysis based on two-point functions. We discuss efficient and accurate inference techniques that allow us to scale the method to the large samples of galaxies to be expected in LSST. We consider statistical challenges like the parametrization of redshift systematics, discuss and evaluate techniques to regularize the sample redshift distributions, and investigate techniques that can help to detect and calibrate sources of systematic error using posterior predictive checks. We evaluate and forecast photometric redshift performance using data from the CosmoDC2 simulations, within which we mimic a DESI-like spectroscopic calibration sample for cross-correlations. Using a combination of spatial cross-correlations and photometry, we show that we can provide calibration of the mean of the sample redshift distribution to an accuracy of at least 0.002(1+z), consistent with the LSST-Y1 science requirements for weak lensing and large-scale structure probes., Comment: Updated to match the version accepted by the MNRAS, 23 pages, 9 figures, 2 tables

With a single training image and using wavelet phase harmonic augmentation, we present polarized Cosmic Microwave Background (CMB) foreground marginalization in a high-dimensional likelihood-free (Bayesian) framework. We demonstrate robust foreground removal using only a single frequency of simulated data for a BICEP-like sky patch. Using Moment Networks we estimate the pixel-level posterior probability for the underlying {E,B} signal and validate the statistical model with a quantile-type test using the estimated marginal posterior moments. The Moment Networks use a hierarchy of U-Net convolutional neural networks. This work validates such an approach in the most difficult limiting case: pixel-level, noise-free, highly non-Gaussian dust foregrounds with a single training image at a single frequency. For a real CMB experiment, a small number of representative sky patches would provide the training data required for full cosmological inference. These results enable robust likelihood-free, simulation-based parameter and model inference for primordial B-mode detection using observed CMB polarization data., Accepted by Monthly Notices of the Royal Astronomical Society Letters. 5 pages with 3 figures (plus 1 page of Supporting Materials with 2 figures)

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

We study gravitational lensing of gravitational waves from compact object binaries as a probe of compact dark matter (DM) objects such as primordial black holes. Assuming a point mass lens, we perform parameter estimation of lensed gravitational wave signals from compact object binaries to determine the detectability of the lens with ground based laser interferometers. Then, considering binary populations that LIGO-Virgo has been probing, we derive a constraint on the abundance of compact DM from non-observation of lensed events. We find that the LIGO-Virgo observations imply that compact objects heavier than $M_l = 200M_\odot$ can not constitute all DM and less than $40\%$ of DM can be in compact objects heavier than $M_l = 400M_\odot$. We also show that the DM fraction in compact objects can be probed by LIGO in its final sensitivity for $M_l > 40M_\odot$ reaching $2\%$ of the DM abundance at $M_l > 200M_\odot$, and by ET for $M_l > 1M_\odot$ reaching DM fraction as low as $7\times 10^{-5}$ at $M_l > 40M_\odot$., 8 pages, 4 figures. published version

The demographics of dark matter substructure depend sensitively on the nature of dark matter. Optimally leveraging this probe requires accurate theoretical predictions regarding the abundance of subhaloes. These predictions are hampered by artificial disruption in numerical simulations, by large halo-to-halo variance, and by the fact that the results depend on the baryonic physics of galaxy formation. In particular, numerical simulations have shown that the formation of a central disc can drastically reduce the abundance of substructure compared to a dark matter-only simulation, which has been attributed to enhanced destruction of substructure due to disc shocking. We examine the impact of discs on substructure using the semi-analytical subhalo model SatGen, which accurately models the tidal evolution of substructure free of the numerical disruption that still hampers $N$-body simulations. Using a sample of 10,000 merger trees of Milky Way-like haloes, we study the demographics of subhaloes that are evolved under a range of composite halo-disc potentials with unprecedented statistical power. We find that the overall subhalo abundance is relatively insensitive to properties of the disc aside from its total mass. For a disc that contains $5\%$ of $M_\mathrm{vir}$, the mean subhalo abundance within $r_\mathrm{vir}$ is suppressed by ${\lesssim}10\%$ relative to the no-disc case, a difference that is dwarfed by halo-to-halo variance. For the same disc mass, the abundance of subhaloes within 50 kpc is reduced by ${\sim}30\%$. We argue that the disc mainly drives excess mass loss for subhaloes with small pericentric radii and that the impact of disc shocking is negligible., 13 pages, 8 figures. Accepted to MNRAS

Hydrodynamic simulations provide a powerful, but computationally expensive, approach to study the interplay of dark matter and baryons in cosmological structure formation. Here we introduce the EMulating Baryonic EnRichment (EMBER) Deep Learning framework to predict baryon fields based on dark-matter-only simulations thereby reducing computational cost. EMBER comprises two network architectures, U-Net and Wasserstein Generative Adversarial Networks (WGANs), to predict two-dimensional gas and HI densities from dark matter fields. We design the conditional WGANs as stochastic emulators, such that multiple target fields can be sampled from the same dark matter input. For training we combine cosmological volume and zoom-in hydrodynamical simulations from the Feedback in Realistic Environments (FIRE) project to represent a large range of scales. Our fiducial WGAN model reproduces the gas and HI power spectra within 10% accuracy down to ~10 kpc scales. Furthermore, we investigate the capability of EMBER to predict high resolution baryon fields from low resolution dark matter inputs through upsampling techniques. As a practical application, we use this methodology to emulate high-resolution HI maps for a dark matter simulation of a L=100 Mpc/h comoving cosmological box. The gas content of dark matter haloes and the HI column density distributions predicted by EMBER agree well with results of large volume cosmological simulations and abundance matching models. Our method provides a computationally efficient, stochastic emulator for augmenting dark matter only simulations with physically consistent maps of baryon fields., 21 pages, 12 figures, accepted by MNRAS, comments welcome

The quest for high-redshift quasars has led to a series of record-breaking sources, with the current record holder at $z=7.642$. Here, we show how future detections of $z>8$ quasars impact the constraints on the parameters for black hole growth and seed models. Using broad flat priors on the growth parameters (Eddington ratio $\,f_{\rm Edd}$, duty cycle ${\cal D}$, seed mass $M_{\rm \bullet, seed}$ and radiative efficiency $\epsilon$), we show that the large uncertainties in their determination decrease by a factor $\sim 5$ when a quasar's detection redshift goes from $z=9$ to $z=12$. In this high-redshift regime, $\epsilon$ tends to the lowest value allowed, and the distribution for $M_{\rm \bullet, seed}$ peaks well inside the heavy seed domain. Remarkably, two quasars detected at $z > 7$ with low accretion rates (J1243+0100 and J0313-1806) already tighten the available parameter space, requiring $M_{\rm \bullet, seed} > 10^{3.5} \,{\rm M_\odot}$ and $\epsilon < 0.1$. The radiative efficiency is a crucial unknown, with factor $\sim 2$ changes able to modify the predicted mass by $\sim 3$ orders of magnitude already at $z\sim 9$. The competing roles of inefficient accretion (decreasing $\epsilon$) and black hole spin-up (increasing $\epsilon$) significantly impact growth models. Finally, we suggest that yields currently predicted by upcoming quasar surveys (e.g., Euclid) will be instrumental for determining the most-likely seed mass regime. For example, assuming thin-disk accretion, a detection of a quasar with $M_\bullet \sim 10^{10} \,{\rm M_\odot}$ by $z\sim 9-10$ would exclude the entire parameter space available for light seeds and dramatically reduce the one for heavy seeds., Comment: Accepted for publication in MNRAS. This is the final version of the manuscript. 8 pages, 5 figures

The first luminous objects forming in the universe produce radiation backgrounds in the far-ultraviolet and X-ray bands that affect the formation of Population III stars. Using a grid of cosmological hydrodynamics zoom-in simulations, we explore the impact of the Lyman–Warner (LW) and X-ray radiation backgrounds on the critical dark matter (DM) halo mass for Population III star formation and the total mass in stars per halo. We find that the LW radiation background lowers the H2 fraction and delays the formation of the Population III stars. On the other hand, X-ray irradiation anticipates the redshift of collapse and reduces the critical halo mass, unless the X-ray background is too strong and gas heating shuts down gas collapse into the haloes and prevents star formation. Therefore, an X-ray background can increase the number of DM haloes forming Population III stars by about a factor of 10, but the total mass in stars forming in each halo is reduced. This is because X-ray radiation increases the molecular fraction and lowers the minimum temperature of the collapsing gas (or equivalently the mass of the quasi-hydrostatic core) and therefore slows down the accretion of the gas on to the central protostar.

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

Scalar Field Dark Matter (SFDM) comprised of ultralight ($\gtrsim 10^{-22}$ eV) bosons is an alternative to standard, collisionless Cold Dark Matter (CDM) that is CDM-like on large scales but inhibits small-scale structure formation. As a Bose-Einstein condensate, its free-field ("fuzzy") limit (FDM) suppresses structure below the de Broglie wavelength, $\lambda_\text{deB}$, creating virialized haloes with central cores of radius $\sim\lambda_\text{deB}$, surrounded by CDM-like envelopes, and a halo mass function (HMF) with a sharp cut-off on small scales. With a strong enough repulsive self-interaction (SI), structure is inhibited, instead, below the Thomas-Fermi (TF) radius, $R_\text{TF}$ (the size of an SI-pressure-supported ($n=1$)-polytrope), when $R_\text{TF} > \lambda_\text{deB}$. Previously, we developed tools to describe SFDM dynamics on scales above $\lambda_\text{deB}$ and showed that SFDM-TF haloes formed by Jeans-unstable collapse from non-cosmological initial conditions have $R_\text{TF}$-sized cores, surrounded by CDM-like envelopes. Revisiting SFDM-TF in the cosmological context, we simulate halo formation by cosmological infall and collapse, and derive its transfer function from linear perturbation theory to produce cosmological initial conditions and predict statistical measures of structure formation, such as the HMF. Since FDM and SFDM-TF transfer functions both have small-scale cut-offs, we can align them to let observational constraints on FDM proxy for SFDM-TF, finding FDM with particle masses $1 \lesssim m/(10^{-22} \text{ eV}/c^2) \lesssim 30$ corresponds to SFDM-TF with $10 \gtrsim R_\text{TF}/(1 \text{ pc}) \gtrsim 1$, favoring sub-galactic (sub-kpc) core-size. The SFDM-TF HMF cuts off gradually, however, leaving more small-mass haloes: its Jeans mass shrinks so fast, scales filtered early can still recover and grow!, Comment: 30 pages, 10 figures, accepted by MNRAS 09/22/21, 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.

We use 78 reverberation-measured Mg II time-lag quasars (QSOs) in the redshift range $0.0033 \leq z \leq 1.89$ to constrain cosmological parameters in six different cosmological models. The basis of our method is the use of the radius-luminosity or $R-L$ relation to standardize these 78 Mg II QSOs. In each cosmological model we simultaneously determine $R-L$ relation and cosmological model parameters, thus avoiding the circularity problem. We find that the $R-L$ relation parameter values are independent of the cosmological model used in the analysis thus establishing that current Mg II QSOs are standardizable candles. Cosmological constraints obtained using these QSOs are significantly weaker than, but consistent with, those obtained from a joint analysis of baryon acoustic oscillation (BAO) observations and Hubble parameter [$H(z)$] measurements. So, we also analyse these QSOs in conjunction with the BAO + $H(z)$ data and find cosmological constraints consistent with the standard spatially-flat $\Lambda$CDM model as well as with mild dark energy dynamics and a little spatial curvature. A larger sample of higher-quality reverberation-measured QSOs should have a smaller intrinsic dispersion and so should provide tighter constraints on cosmological parameters., Comment: 16 pages, 11 figure, Mg II QSO data are given, MNRAS accepted version. arXiv admin note: text overlap with arXiv:2105.12692

The Laser Interferometer Space Antenna (LISA) will open the mHz frequency window of the gravitational wave (GW) landscape. Among all the new GW sources expected to emit in this frequency band, extreme mass-ratio inspirals (EMRIs) constitute a unique laboratory for astrophysics and fundamental physics. Here we show that EMRIs can also be used to extract relevant cosmological information, complementary to both electromagnetic (EM) and other GW observations. By using the loudest EMRIs (SNR$>$100) detected by LISA as dark standard sirens, statistically matching their sky localisation region with mock galaxy catalogs, we find that constraints on $H_0$ can reach $\sim$1.1% ($\sim$3.6%) accuracy, at the 90% credible level, in our best (worst) case scenario. By considering a dynamical dark energy (DE) cosmological model, with $\Lambda$CDM parameters fixed by other observations, we further show that in our best (worst) case scenario $\sim$5.9% ($\sim$12.3%) relative uncertainties at the 90% credible level can be obtained on $w_0$, the DE equation of state parameter. Besides being relevant in their own right, EMRI measurements will be affected by different systematics compared to both EM and ground-based GW observations. Cross validation with complementary cosmological measurements will therefore be of paramount importance, especially if convincing evidence of physics beyond $\Lambda$CDM emerges from future observations., Comment: 22 pages, 9 figures. v2: new author in author list, new sub-Appendix with additional results, new Fig. A1; some explicative paragraphs added, Fig. 3 updated. Matches the journal version

A clump moving through the intracluster medium of a galaxy cluster can drive a bow shock trailed by a bullet-like core. In some cases, such as in the prototypical Bullet cluster, X-rays show a gas bullet with a protruding head and pronounced shoulders. We point out that these features, while difficult to explain without dark matter (DM), naturally arise as the head of the slowed-down gas is gravitationally pulled forward toward its unhindered DM counterpart. X-ray imaging thus provides a unique, robust probe of the offset, collisionless DM, even without gravitational lensing or other auxiliary data. Numerical simulations and a toy model suggest that the effect is common in major mergers, is often associated with a small bullet-head radius of curvature, and may lead to distinct bullet morphologies, consistent with observations., Comment: 9 pages, 3 figures, comments welcome

The first generation (Pop-III) stars can ionize 1-10% of the universe by $z=15$, when the metal-enriched (Pop-II) stars may contribute negligibly to the ionization. This low ionization tail might leave detectable imprints on the large-scale CMB E-mode polarization. However, we show that physical models for reionization are unlikely to be sufficiently extended to detect any parameter beyond the total optical depth through reionization. This result is driven in part by the total optical depth inferred by Planck, indicating a reionization midpoint around $z=8$, which in combination with the requirement that reionization completes by $z\approx 5.5$ limits the amplitude of an extended tail. To demonstrate this, we perform semi-analytic calculations of reionization including Pop-III star formation in minihalos with Lyman-Werner feedback. We find that standard Pop-III models need to produce very extended reionization at $z>15$ to be distinguishable at 2-$��$ from Pop-II-only models, assuming a cosmic variance-limited measurement of the low-$\ell$ EE power spectrum. However, we show that unless there is (1) a late-time quenching mechanism such as from strong X-ray feedback or (2) some other extreme Pop-III scenario, structure formation makes it quite challenging to produce high enough Thomson scattering optical depth from $z>15$, $��(z>15)$, and still be consistent with other observational constraints on reionization., 11 pages 4 figures + appendix

We present the v1.0 release of CLMM, an open source Python library for the estimation of the weak lensing masses of clusters of galaxies. CLMM is designed as a standalone toolkit of building blocks to enable end-to-end analysis pipeline validation for upcoming cluster cosmology analyses such as the ones that will be performed by the LSST-DESC. Its purpose is to serve as a flexible, easy-to-install and easy-to-use interface for both weak lensing simulators and observers and can be applied to real and mock data to study the systematics affecting weak lensing mass reconstruction. At the core of CLMM are routines to model the weak lensing shear signal given the underlying mass distribution of galaxy clusters and a set of data operations to prepare the corresponding data vectors. The theoretical predictions rely on existing software, used as backends in the code, that have been thoroughly tested and cross-checked. Combined, theoretical predictions and data can be used to constrain the mass distribution of galaxy clusters as demonstrated in a suite of example Jupyter Notebooks shipped with the software and also available in the extensive online documentation., 21 pages, 6 figures, accepted for publication by MNRAS

Bulk of various astronomical observations of black holes suggest that virtually all observed black holes can be of primordial origin. A modified mechanism of the primordial black hole formation is described. A universal log-normal mass spectrum with a mean mass of around $\sim 10 M_\odot$ predicted by this mechanism is strongly confirmed by the LIGO/Virgo observations of gravitational waves from coalescing binary black holes., 10 pages,2 figures, plenary talk at the Fourth Zeldovich meeting, Belarus, Minsk, September 7-11, 2020

Active galactic nuclei (AGN) forming in the early universe are thought to be the primary source of hard ionizing photons contributing to the reionization of intergalactic helium. However, the number density and spectral properties of high-redshift AGN remain largely unconstrained. In this work, we make use of physically-informed models calibrated with a wide variety of available observations to provide estimates for the role of AGN throughout the Epoch of Reionization. We present AGN luminosity functions in various bands between z = 2 to 7 predicted by the well-established Santa Cruz semi-analytic model, which includes modelling of black hole accretion and AGN feedback. We then combine the predicted AGN populations with a physical spectral model for self-consistent estimates of ionizing photon production rates, which depend on the mass and accretion rate of the accreting supermassive black hole. We then couple the predicted comoving ionizing emissivity with an analytic model to compute the subsequent reionization history of intergalactic helium and hydrogen. This work demonstrates the potential of coupling physically motivated analytic or semi-analytic techniques to capture multi-scale physical processes across a vast range of scales (here, from AGN accretion disks to cosmological scales). Our physical model predicts an intrinsic ionizing photon budget well above many of the estimates in the literature, meaning that helium reionization can comfortably be accomplished even with a relatively low escape fraction. We also make predictions for the AGN populations that are expected to be detected in future \emph{James Webb Space Telescope} surveys., Comment: 28 pages, 23 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

Accurate estimation of the Cosmic Microwave Background (CMB) angular power spectrum is enticing due to the prospect for precision cosmology it presents. Galactic foreground emissions, however, contaminate the CMB signal and need to be subtracted reliably in order to lessen systematic errors on the CMB temperature estimates. Typically bright foregrounds in a region lead to further uncertainty in temperature estimates in the area even after some foreground removal technique is performed and hence determining the underlying full-sky angular power spectrum poses a challenge. We explore the feasibility of utilizing artificial neural networks to predict the angular power spectrum of the full sky CMB temperature maps from the observed angular power spectrum of the partial sky in which CMB temperatures in some bright foreground regions are masked. We present our analysis at large angular scales with two different masks. We produce unbiased predictions of the full-sky angular power spectrum and recover the underlying theoretical power spectrum using neural networks. Our predictions are also uncorrelated to a large extent. We further show that the multipole-space covariances of the predictions of full-sky spectra made by the ANNs are much smaller than those of the estimates obtained using the pseudo-$C_\ell$ method., Comment: 10 pages, 11 figures; altered methodology, added links to references, updated analysis using latest available data, modified the write-up accordingly

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

We apply for the first time Gaussian Process Regression (GPR) as a foreground removal technique in the context of single-dish, low redshift HI intensity mapping, and present an open-source Python toolkit for doing so. We use MeerKAT and SKA1-MID-like simulations of 21cm foregrounds (including polarisation leakage), HI cosmological signal and instrumental noise. We find that it is possible to use GPR as a foreground removal technique in this context, and that it is better suited in some cases to recover the HI power spectrum than Principal Component Analysis (PCA), especially on small scales. GPR is especially good at recovering the radial power spectrum, outperforming PCA when considering the full bandwidth of our data. Both methods are worse at recovering the transverse power spectrum, since they rely on frequency-only covariance information. When halving our data along frequency, we find that GPR performs better in the low frequency range, where foregrounds are brighter. It performs worse than PCA when frequency channels are missing, to emulate RFI flagging. We conclude that GPR is an excellent foreground removal option for the case of single-dish, low redshift HI intensity mapping in the absence of missing frequency channels. Our Python toolkit gpr4im and the data used in this analysis are publicly available on GitHub., 19 pages, 1 table, 13 figures, main results in figures 6 and 9, code and data available at https://github.com/paulassoares/gpr4im. Version accepted by 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)

We use galaxies from the IllustrisTNG, MassiveBlack-II and Illustris hydrodynamic simulations to investigate the behaviour of large scale galaxy intrinsic alignments. Our analysis spans four redshift slices over the approximate range of contemporary lensing surveys $z=0-1$. We construct comparable weighted samples from the three simulations, which we then analyse using an alignment model that includes both linear and quadratic alignment contributions. Our data vector includes galaxy-galaxy, galaxy-shape and shape-shape projected correlations, with the joint covariance matrix estimated analytically. In all of the simulations, we report non-zero IAs at the level of several $\sigma$. For a fixed lower mass threshold, we find a relatively strong redshift dependence in all three simulations, with the linear IA amplitude increasing by a factor of $\sim 2$ between redshifts $z=0$ and $z=1$. We report no significant evidence for non-zero values of the tidal torquing amplitude, $A_2$, in TNG, above statistical uncertainties, although MassiveBlack-II favours a moderately negative $A_2\sim-2$. Examining the properties of the TATT model as a function of colour, luminosity and galaxy type (satellite or central), our findings are consistent with the most recent measurements on real data. We also outline a novel method for constraining the TATT model parameters directly from the pixelised tidal field, alongside a proof of concept exercise using TNG. This technique is shown to be promising, although the comparison with previous results obtained via other methods is non-trivial., Comment: 28 pages, 18 Figures; submitted to MNRAS

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 the post-reionization era, the baryons assembled into the protogalaxies and eventually the present population of the galaxies evolved through merger and evolution. In this work, we discuss a possible probe of the statistical distribution and evolution of the H I density in the post reionization era. We introduce an estimator of the H I power spectrum from the post reionization universe by observing it through the strong gravitational lenses by the nearby galaxy cluster. We also analytically calculate the uncertainties associated with the estimates of the post-EoR power spectrum for the discussed estimator. We access the efficacy of this estimator in the context of 19 galaxy clusters for which the lensing potential has been estimated earlier by various authors. We find that by combining the lensed power spectrum through eight of these cluster lenses, it is possible to estimate the post-reionization H I power spectrum at five-sigma significance for angular multipoles < 4000 for a uGMRT observation of 16 MHz bandwidth from redshifts of 1.25, 1.5 with a total of 400 hours of observation. With the same setup, for a redshift of 3.0, we need 200 hours of total observation time. The estimator also suppresses the diffused galactic foreground, though, the latter is still a dominant contributor to the overall signal and hence need to be estimated and mitigated. We discuss the merits and demerits of the estimator., 11 pages, 6 figures

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

We present the analysis of deep X-ray observations of 10 massive galaxy clusters at redshifts $1.05 < z < 1.71$, with the primary goal of measuring the metallicity of the intracluster medium (ICM) at intermediate radii, to better constrain models of the metal enrichment of the intergalactic medium. The targets were selected from X-ray and Sunyaev-Zel'dovich (SZ) effect surveys, and observed with both the \textit{XMM-Newton} and \textit{Chandra} satellites. For each cluster, a precise gas mass profile was extracted, from which the value of $r_{500}$ could be estimated. This allows us to define consistent radial ranges over which the metallicity measurements can be compared. In general, the data are of sufficient quality to extract meaningful metallicity measurements in two radial bins, $r, Comment: 10 pages, 5 figures

Cosmological shock waves are ubiquitous to cosmic structure formation and evolution. As a consequence, they play a major role in the energy distribution and thermalization of the intergalactic medium (IGM). We analyze the Mach number distribution in the Dianoga simulations of galaxy clusters performed with the SPH code GADGET-3. The simulations include the effects of radiative cooling, star formation, metal enrichment, supernova and active galactic nuclei feedback. A grid-based shock-finding algorithm is applied in post-processing to the outputs of the simulations. This procedure allows us to explore in detail the distribution of shocked cells and their strengths as a function of cluster mass, redshift and baryonic physics. We also pay special attention to the connection between shock waves and the cool-core/non-cool core (CC/NCC) state and the global dynamical status of the simulated clusters. In terms of general shock statistics, we obtain a broad agreement with previous works, with weak (low-Mach number) shocks filling most of the volume and processing most of the total thermal energy flux. As a function of cluster mass, we find that massive clusters seem more efficient in thermalising the IGM and tend to show larger external accretion shocks than less massive systems. We do not find any relevant difference between CC and NCC clusters. However, we find a mild dependence of the radial distribution of the shock Mach number on the cluster dynamical state, with disturbed systems showing stronger shocks than regular ones throughout the cluster volume., Comment: 19 pages, 15 figures, accepted for publication in MNRAS

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

We numerically study the movement of two colliding fuzzy dark matter solitons without explicit self-interaction and find the effective cross section of dissipative change in velocity. The cross section turns out to be inversely proportional to the velocity cubed, and we present its analytic interpretation. Using the result we roughly estimate spatial offsets during head-on collisions of two fuzzy dark matter halos, which can be related to the spatial offsets between stars and dark matter in collisions of some galaxy clusters. We also show that the gravitational cooling plays an important role during the collisions., To be published in JKPS

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

The Internal Linear Combination (ILC) method has been extensively used to extract the cosmic microwave background (CMB) anisotropy map from foreground contaminated multi-frequency maps. However, the performance of simple ILC is limited and can be significantly improved by heavily constraint equations, dubbed cILC. The standard ILC and cILC works on the spin-0 field. Recently, a generalized version of ILC is developed to estimate polarization maps in which the quantity $Q \pm iU$ is combined at multiple frequencies using complex coefficients called Polarization ILC (PILC). A statistical moment expansion method has recently been developed for high precision modelling of the Galactic foregrounds. This paper develops a semi-blind component separation method combining the moment approach of foreground modelling with a generalized version of the PILC method for heavily constraint equations. The algorithm is developed in pixel space and performs for a spin-2 field. We employ this component separation technique in simultaneous estimation of Stokes $Q$, $U$ maps of the thermal dust at 353 GHz and synchrotron at 30 GHz over 78 % of the sky. We demonstrate the performance of the method on three sets of absolutely calibrated simulated maps at WMAP and planck frequencies with varying foreground models., Comment: 23 pages, 16 figures, Submitted to MNRAS

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