arXiv subjects

Anatoly Klypin

Publications and source records attributed to Anatoly Klypin.

At least 19 recordsLinked to original sources

arXiv2026

Galaxies at z > 10: ΛCDM predicts increased Star Formation Efficiency

We show that the rest-frame UV statistics and global properties of galaxies at 7 <= z <= 14 are naturally reproduced within the standard ΛCDM framework when galaxy formation is modeled with UniverseMachine applied to the high-resolution Uchuu N-body simulation. Our model matches the UV luminosity functions over five magnitudes and reproduces the evolution of the UV (and inferred star formation rate) density once internal dust attenuation is included. Comparisons with spectroscopically confirmed JWST/HST galaxies show good agreement with the stellar mass-SFR and stellar mass-UV luminosity relations. In contrast, earlier claims of insufficient stellar masses at z=8 are inconsistent with our model and are likely driven by systematic uncertainties, including AGN contamination, dust attenuation, and the lack of JWST/MIRI constraints. A key prediction is that the star-formation efficiency increases with redshift at fixed halo mass, reaching 2-3 percent of baryons converted into stars by z=10-12. These results demonstrate that current JWST observations of early galaxy populations can be explained within the ΛCDM framework.

astro-ph.GA↗

arXiv2026

Hidden Connections: Tracing the BCG Stellar Mass-Halo Mass Relation in the SDSS-GalWCat19 Cluster Catalog

The stellar-to-halo mass (SMHM) relation of brightest cluster galaxies (BCGs) provides key insight into the connection between BCG growth and the assembly of their host halos. We analyze this relation using the spectroscopic SDSS GalWCat19 cluster catalog, selecting 996 systems with log(M200) >= 13.6, log(Mstar) >= 10.5, and 0.02 <= z <= 0.125 to limit evolutionary effects and ensure stellar-mass completeness. We fit lognormal scaling relations with a Markov Chain Monte Carlo (MCMC) framework that accounts for measurement uncertainties and intrinsic scatter. For the fiducial SMHM relation, = alpha + beta log(M200/Mpiv) with log(Mpiv) = 14.2, we find a shallow slope beta = 0.17 +/- 0.03, normalization alpha = 11.04 +/- 0.01, and intrinsic scatter sigma_int = 0.19 +/- 0.01 dex. Recasting the relation in normalized form reduces the scatter to 0.16 +/- 0.01 dex, while including the magnitude gap M14 further reduces it to 0.14 +/- 0.01 dex. Variations in richness, redshift, and mass thresholds produce systematic shifts that are small compared to the statistical uncertainties, indicating that our inferred relations are robust to plausible selection choices. The reduced scatter when including M14 supports a picture in which BCG stellar mass reflects both halo mass and halo assembly history.

astro-ph.GA↗

arXiv2026

A redshift-independent theoretical halo mass function validated with Uchuu simulations

We present a new theoretical framework for the halo mass function (HMF) that accurately predicts the abundance of dark matter haloes across an exceptionally wide range in mass and redshift. Building on a generalised Press & Schechter model and triaxial collapse (GPS+), we predict the HMF in terms of the variance of the linear density field, with only a weak explicit dependence on halo mass and no explicit dependence on redshift. The GPS+ model naturally provides the correct normalization and high-mass behaviour without requiring empirical fitting. We calibrate and validate the GPS+ model using the Uchuu N-body simulation suite, which combines large cosmological volume and high mass resolution under Planck cosmology. Using six simulations with up to 300 realizations, we obtain precision HMF measurements spanning halo masses in the range 6.5 < log($M_{\rm 200m}$/[h$^{-1}$ $M_{\odot}$]) <16 over 0 < z < 20, with reduced cosmic variance. Across this full domain, the GPS+ model reproduces the simulated HMF with deviations typically below 10-20%. Comparison with the Sheth-Tormen (ST) model shows similar performance at z < 2, but markedly improved agreement at higher redshifts, where ST can deviate by 70-80% while our model remains within ~20%. Finally, we assess the impact of the halo mass definition: adopting the evolving virial overdensity of Bryan & Norman (1998) worsens agreement at low redshift and high masses, whereas M200m yields a more universal, nearly redshift-independent HMF.

astro-ph.CO↗

arXiv2025

Constraining cosmological parameters using void statistics from the SDSS survey

We identify voids as maximal non-overlapping spheres within the haloes of the Uchuu simulation and three smaller halo simulation boxes with smaller volume and different $σ_{8}$ values, and galaxies with redshift in the range $0.02<z<0.132$ and absolute magnitude in the $r-$band $M_{r}<-20.5$ of 32 Uchuu-SDSS simulated lightcones the seventh release of \textit{The Sloan Digital Sky Survey} (SDSS DR7) survey. We compute the Void Probability Function and the abundance of voids larger than $r$ predicted by the theoretical framework used in this work and we check that it predicts successfully both void functions for the halo simulation boxes. Next, we asses the potential of this theoretical framework to constrain cosmological parameters using Uchuu-SDSS void statistics, and we calculate the confidence levels using Monte Carlo Markov Chain techniques to infer the values of $σ_{8}$, $Ω_{\rm m}$ and H$_{0}$ from the SDSS sample used. The constraints we obtain from the SDSS survey sample used. The results are: $σ_{8}=1.028^{+0.273}_{-0.305}$, $Ω_{\rm m}=0.296^{+0.110}_{-0.102}$, H$_{0}=83.43\pm^{+29.27}_{-27.70}$, $Γ=0.1947^{+0.0578}_{-0.0516}$ and S$_{8}$=1.017$^{+0.363}_{-0.359}$. If we combine these constraints with KiDS-1000+DESY3, we get $σ_{8}=0.858^{+0.040}_{-0.040}$, $Ω_{\rm m}=0.257\pm^{+0.023}_{-0.020}$, H$_{0}=74.17^{+4.66}_{-4.66}$ and S$_{8}$=0.794$^{+0.016}_{-0.016}$. The combined uncertainties are approximately a factor 2-3 smaller than only-Weak-Lensing uncertainties. This is a consequence of the orientation of the confidence level contours of SDSS voids and Weak Lensing in the plane $σ_{8}-Ω_{\rm m}$, which are almost orthogonal (abridged).

astro-ph.CO↗

arXiv2024

The Uchuu-GLAM BOSS and eBOSS LRG lightcones: Exploring clustering and covariance errors

This study investigates the clustering and bias of Luminous Red Galaxies (LRG) in the BOSS-LOWZ, -CMASS, -COMB, and eBOSS samples, using two types of simulated lightcones: (i) high-fidelity lightcones from Uchuu $N$-body simulation, employing SHAM technique to assign LRG to (sub)halos, and (ii) 16000 covariance lightcones from GLAM-Uchuu $N$-body simulations, including LRG using HOD data from Uchuu. Our results indicate that Uchuu and GLAM lightcones closely replicate BOSS/eBOSS data, reproducing correlation function and power spectrum across scales from redshifts $0.2$ to $1.0$, from $2$ to $150\,h^{-1}\mathrm{Mpc}$ in configuration space, from $0.005$ to $0.7\,h\mathrm{Mpc}^{-1}$ in Fourier space, and across different LRG stellar masses. Furthermore, comparing with existing MD-Patchy and EZmock BOSS/eBOSS lightcones based on approximate methods, our GLAM-Uchuu lightcones provide more precise clustering estimates. We identify significant deviations from observations within $20\,h^{-1}\mathrm{Mpc}$ scales in MD-Patchy and EZmock, with our covariance matrices indicating that these methods underestimate errors by between $10\%$ and $60\%$. Lastly, we explore the impact of cosmology on galaxy clustering. Our findings suggest that, given the current level of uncertainties in BOSS/eBOSS data, distinguishing models with and without massive neutrino effects on LSS is challenging. This paper highlights the Uchuu and GLAM-Uchuu simulations' robustness in verifying the accuracy of Planck cosmological parameters, providing a strong foundation for enhancing lightcone construction in future LSS surveys. We also demonstrate that generating thousands of galaxy lightcones is feasible using $N$-body simulations with adequate mass and force resolution.

astro-ph.CO↗

arXiv2023

The Correlation Function and Detection of Baryon Acoustic Oscillation Peak from the Spectroscopic SDSS GalWCat Galaxy Cluster Catalogue

We measure the two point correlation function (CF) of 1357 galaxy clusters with a mass of $\log_{10}{M_{200}}\geq 13.6$~\hm~and at a redshift of $z \leq 0.125$. This work differs from previous analyses in that it utilizes a spectroscopic cluster catalogue, $\mathtt{SDSS-GalWCat}$, to measure the CF and detect the baryon acoustic oscillation (BAO) signal. Unlike previous studies which use statistical techniques, we compute covariance errors directly by generating a set of 1086 galaxy cluster lightcones from the GLAM $N$-body simulation. Fitting the CF with a power-law model of the form $ξ(s) = (s/s_0)^{-γ}$, we determine the best-fit correlation length and power-law index at three mass thresholds. We find that the correlation length increases with increasing the mass threshold while the power-law index is almost constant. For $\log_{10}{M_{200}}\geq 13.6$~\hm, we find $s_0 = 14.54\pm0.87$~\h~and $γ=1.97\pm0.11$. We detect the BAO signal at $s = 100$~\h~with a significance of $1.60 σ$. Fitting the CF with a $Λ$CDM model, we find $D_\mathrm{V}(z = 0.089)\mathrm{r}^{fid}_d/\mathrm{r}_d = 267.62 \pm 26$ \h, consistent with Planck 2015 cosmology. We present a set of 108 high-fidelity simulated galaxy cluster lightcones from the high-resolution \U~N-body simulation, employed for methodological validation. We find $D_\mathrm{V}(z = 0.089)/r_d = 2.666 \pm 0.129$, indicating that our method does not introduce any bias in the parameter estimation for this small sample of galaxy clusters.

astro-ph.CO↗

arXiv2023

Confirmation of the standard cosmological model from red massive galaxies $\sim600$ Myr after the Big Bang

In their recent study, Labbé et al. used multi-band infrared images captured by the James Webb Space Telescope (JWST) to discover a population of red massive galaxies that formed approximately 600 million years after the Big Bang. The authors reported an extraordinarily large density of these galaxies, with stellar masses exceeding $10^{10}$ solar masses, which, if confirmed, challenges the standard cosmological model as suggested by recent studies. However, this conclusion is disputed. We contend that during the early epochs of the universe the stellar mass-to-light ratio could not have reached the values reported by Labbé et al. A model of galaxy formation based on standard cosmology provides support for this hypothesis, predicting the formation of massive galaxies with higher ultraviolet (UV) luminosity, which produce several hundred solar masses of stars per year and containing significant dust. These forecasts are consistent with the abundance of JWST/HST galaxies selected photometrically in the rest-frame UV wavelengths and with the properties of the recent spectroscopically-confirmed JWST/HST galaxies formed during that era. Discrepancies with Labbé et al. may arise from overestimation of the stellar masses, systematic uncertainties, absence of JWST/MIRI data, heavy dust extinction affecting UV luminosities, or misidentification of faint red AGN galaxies at closer redshifts. The current JWST/HST results, combined with a realistic galaxy formation model, provide strong confirmation of the standard cosmology.

astro-ph.GA↗

arXiv2022

The Uchuu-UniverseMachine dataset: Galaxies in and around Clusters

We present the public data release of the Uchuu-UM galaxy catalogues by applying the UniverseMachine algorithm to assign galaxies to the dark matter halos in the Uchuu $N$-body cosmological simulation. It includes a variety of baryonic properties for all galaxies down to $\sim 5\times10^8 M_{\odot}$ with halos in a mass range of $10^{10}<M_{\rm halo}/M_{\odot}<5\times10^{15}$ up to redshift $z=10$. Uchuu-UM includes more than $10^{4}$ cluster-size halos in a volume of $ 8(h^{-1} {\rm Gpc})^3$, reproducing observed stellar mass functions across the redshift range of $z=0-7$, galaxy quenched fractions, and clustering statistics at low redshifts. Compared to the previous largest UM catalogue, the Uchuu-UM catalogue includes significantly more massive galaxies hosted by large-mass dark matter halos. Overall, the number density profile of galaxies in dark matter halos follows the dark matter profile, with the profile becoming steeper around the splashback radius and flattening at larger radii. The number density profile of galaxies tends to be steeper for larger stellar masses and depends on the color of galaxies, with red galaxies having steeper slopes at all radii than blue galaxies. The quenched fraction exhibits a strong dependence on the stellar mass and increases toward the inner regions of clusters. The publicly available Uchuu-UM galaxy catalogue presented here can serve to model ongoing and upcoming large galaxy surveys.

astro-ph.GA↗

arXiv2022

Constraining Cosmological Parameters using the Cluster Mass-Richness Relation

The cluster mass-richness relation (MRR) is an observationally efficient and potentially powerful cosmological tool for constraining the mean matter density of the universe and the amplitude of fluctuations using the cluster abundance technique. We derive the MRR relation using GalWCat19, a publicly available galaxy cluster catalog we created from the Sloan Digital Sky Survey-DR13 spectroscopic dataset. The MRR shows a tail at the low-richness end. Using the Illustris-TNG and mini-Uchuu cosmological numerical simulations, we demonstrate that this tail is caused by systematical uncertainties. We show that, by means of a judicious cut, identified by the use of the Hinge function, it is possible to determine a richness threshold above which the MRR is linear i.e., where cluster mass scales with richness as logM_200 = alpha + beta logN_200. We derive the MRR and show it is consistent with both sets of simulations with a slope of beta ~ 1. We use our MRR to estimate cluster masses from the GalWCat19 catalog which we then use to set constraints on omega_m and sigma_8. Utilizing the all-member MRR, we obtain constraints of omega_m = 0.31 (+0.04-0.03) and sigma_8 = 0.82 (+0.05-0.04), and utilizing the red-member MRR, we obtain omega_m = 0.31 (+0.04-0.03) and sigma_8 = 0.81 (+0.05-0.04). Our constraints on omega_m and sigma_8 are consistent and very competitive with the Planck 2018 results.

astro-ph.CO↗

arXiv2022

Fast full N-body simulations of generic modified gravity: conformal coupling models

We present MG-GLAM, a code developed for the very fast production of full $N$-body cosmological simulations in modified gravity (MG) models. We describe the implementation, numerical tests and first results of a large suite of cosmological simulations for three classes of MG models with conformal coupling terms: the $f(R)$ gravity, symmetron and coupled quintessence models. Derived from the parallel particle-mesh code GLAM, MG-GLAM incorporates an efficient multigrid relaxation technique to solve the characteristic nonlinear partial differential equations of these models. For $f(R)$ gravity, we have included new variants to diversify the model behaviour, and we have tailored the relaxation algorithms to these to maintain high computational efficiency. In a companion paper, we describe versions of this code developed for derivative coupling MG models, including the Vainshtein- and K-mouflage-type models. MG-GLAM can model the prototypes for most MG models of interest, and is broad and versatile. The code is highly optimised, with a tremendous speedup of a factor of more than a hundred compared with earlier $N$-body codes, while still giving accurate predictions of the matter power spectrum and dark matter halo abundance. MG-GLAM is ideal for the generation of large numbers of MG simulations that can be used in the construction of mock galaxy catalogues and the production of accurate emulators for ongoing and future galaxy surveys.

astro-ph.CO↗

arXiv2021

Fast full $N$-body simulations of generic modified gravity: derivative coupling models

We present MG-GLAM, a code developed for the very fast production of full $N$-body cosmological simulations in modified gravity (MG) models. We describe the implementation, numerical tests and first results of a large suite of cosmological simulations for two broad classes of MG models with derivative coupling terms -- the Vainshtein- and Kmouflage-type models -- which respectively features the Vainshtein and Kmouflage screening mechanism. Derived from the parallel particle-mesh code GLAM, MG-GLAM incorporates an efficient multigrid relaxation technique to solve the characteristic nonlinear partial differential equations of these models. For Kmouflage, we have proposed a new algorithm for the relaxation solver, and run the first simulations of the model to understand its cosmological behaviour. In a companion paper, we describe versions of this code developed for conformally-coupled MG models, including several variants of $f(R)$ gravity, the symmetron model and coupled quintessence. Altogether, MG-GLAM has so far implemented the prototypes for most MG models of interest, and is broad and versatile. The code is highly optimised, with a tremendous (over two orders of magnitude) speedup when comparing its running time with earlier $N$-body codes, while still giving accurate predictions of the matter power spectrum and dark matter halo abundance. MG-GLAM is ideal for the generation of large numbers of MG simulations that can be used in the construction of mock galaxy catalogues and accurate emulators for ongoing and future galaxy surveys.

astro-ph.CO↗

arXiv2021

Evolution of skewness and kurtosis of cosmic density fields

Methods. We perform numerical simulations of the evolution of the cosmic web for the conventional LCDM model. The simulations cover a wide range of box sizes L = 256 - 4000 Mpc/h, mass and force resolutions and epochs from very early moments z = 30 to the present moment z = 0. We calculate density fields with various smoothing lengths to find the dependence of the density field on smoothing scale. We calculate PDF and its moments - variance, skewness and kurtosis. Results. We focus on the third (skewness S) and fourth (kurtosis K) moments of the distribution functions: their dependence on the smoothing scale, the amplitude of fluctuations and the redshift. During the evolution the reduced skewness $S_3= S/σ$ and reduced kurtosis $S_4=K/σ^2$ present a complex behaviour: at a fixed redshift curves of $S_3(σ)$ and $S_4(σ)$ steeply increase with $σ$ at $σ\le 1$ and then flatten out and become constant at $σ\ge2$. If we fix the smoothing scale $R_t$, then after reaching the maximum at $σ\approx 2$, the curves at large $σ$ start to gradually decline. We provide accurate fits for the evolution of $S_{3,4}(σ,z)$. Skewness and kurtosis approach at early epochs constant levels, depending on smoothing length: $S_3(σ) \approx 3$ and $S_4(σ) \approx 15$. Conclusions. Most of statistics of dark matter clustering (e.g., halo mass function or concentration-mass relation) are nearly universal: they mostly depend on the $σ$ with the relatively modest correction to explicit dependence on the redshift. We find just the opposite for skewness and kurtosis: the dependence of moments on evolutionary epoch $z$ and smoothing length $R_t$ is very different, together they determine the evolution of $S_{3,4}(σ)$ uniquely. The evolution of $S_3$ and $S_4$ cannot be described by current theoretical approximations.

astro-ph.CO↗

arXiv2020

Full-sky photon simulation of clusters and active galactic nuclei in the soft X-rays for eROSITA

The eROSITA X-ray telescope on board the Spectrum-Roentgen-Gamma (SRG) mission will measure the position and properties of about 100,000 clusters of galaxies and 3 million active galactic nuclei over the full sky. To study the statistical properties of this ongoing survey, it is key to estimate the selection function accurately. We create a set of full sky light-cones using the MultiDark and UNIT dark matter only N-body simulations. We present a novel method to predict the X-ray emission of galaxy clusters. Given a set of dark matter halo properties (mass, redshift, ellipticity, offset parameter), we construct an X-ray emissivity profile and image for each halo in the light-cone. We follow the eROSITA scanning strategy to produce a list of X-ray photons on the full sky. We predict scaling relations for the model clusters, which are in good agreement with the literature. The predicted number density of clusters as a function of flux also agrees with previous measurements. Finally, we obtain a scatter of 0.21 (0.07, 0.25) for the X-ray luminosity -- mass (temperature -- mass, luminosity -- temperature) model scaling relations. We provide catalogues with the model photons emitted by clusters and active galactic nuclei. These catalogues will aid the eROSITA end to end simulation flow analysis and in particular the source detection process and cataloguing methods.

astro-ph.CO↗

arXiv2020

Cosmological Constraint on $Ω_m$ and $σ_8$ from Cluster Abundances using the $\mathtt{GalWCat19}$ Optical-Spectroscopic SDSS Catalog

We derive cosmological constraints on the matter density, \om, and the amplitude of fluctuations, \sig, using $\mathtt{GalWCat19}$, a catalog of 1800 galaxy clusters we identified in the Sloan Digital Sky Survey-DR13 spectroscopic data set using our GalWeight technique to determine cluster membership \citep{Abdullah18,Abdullah19}. By analyzing a subsample of 756 clusters in a redshift range of $0.045\leq z \leq 0.125$ and virial masses of $M\geq 0.8\times10^{14}$ \hm ~with mean redshift of $z = 0.085$, we obtain \om ~$=0.310^{+0.023}_{-0.027} \pm 0.041$ (systematic) and \sig ~$=0.810^{+0.031}_{-0.036}\pm 0.035$ (systematic), with a cluster normalization relation of $σ_8= 0.43 Ω_m^{-0.55}$. There are several unique aspects to our approach: we use the largest spectroscopic data set currently available, and we assign membership using the GalWeight technique which we have shown to be very effective at simultaneously maximizing the number of {\it{bona fide}} cluster members while minimizing the number of contaminating interlopers. Moreover, rather than employing scaling relations, we calculate cluster masses individually using the virial mass estimator. Since $\mathtt{GalWCat19}$ is a low-redshift cluster catalog we do not need to make any assumptions about evolution either in cosmological parameters or in the properties of the clusters themselves. Our constraints on \om ~and \sig ~are consistent and very competitive with those obtained from non-cluster abundance cosmological probes such as Cosmic Microwave Background (CMB), Baryonic Acoustic Oscillation (BAO), and supernovae (SNe). The joint analysis of our cluster data with Planck18+BAO+Pantheon gives \om ~$=0.315^{+0.013}_{-0.011}$ and \sig ~$=0.810^{+0.011}_{-0.010}$.

astro-ph.CO↗

arXiv2020

The Completed SDSS-IV Extended Baryon Oscillation Spectroscopic Survey: GLAM-QPM mock galaxy catalogs for the Emission Line Galaxy Sample

We present 2000 mock galaxy catalogs for the analysis of baryon acoustic oscillations in the Emission Line Galaxy (ELG) sample of the Extended Baryon Oscillation Spectroscopic Survey Data Release 16 (eBOSS DR16). Each mock catalog has a number density of $6.7 \times 10^{-4} h^3 \rm Mpc^{-3}$, covering a redshift range from 0.6 to 1.1. The mocks are calibrated to small-scale eBOSS ELG clustering measurements at scales of around 10 $h^{-1}$Mpc. The mock catalogs are generated using a combination of GaLAxy Mocks (GLAM) simulations and the Quick Particle-Mesh (QPM) method. GLAM simulations are used to generate the density field, which is then assigned dark matter halos using the QPM method. Halos are populated with galaxies using a halo occupation distribution (HOD). The resulting mocks match the survey geometry and selection function of the data, and have slightly higher number density which allows room for systematic analysis. The large-scale clustering of mocks at the baryon acoustic oscillation (BAO) scale is consistent with data and we present the correlation matrix of the mocks.

astro-ph.CO↗

arXiv2020

Clustering and Halo Abundances in Early Dark Energy Cosmological Models

LCDM cosmological models with Early Dark Energy (EDE) have been proposed to resolve tensions between the Hubble constant H0 = 100h km/s/Mpc measured locally, giving h ~ 0.73, and H0 deduced from Planck cosmic microwave background (CMB) and other early universe measurements plus LCDM, giving h ~ 0.67. EDE models do this by adding a scalar field that temporarily adds dark energy equal to about 10% of the cosmological energy density at the end of the radiation-dominated era at redshift z ~ 3500. Here we compare linear and nonlinear predictions of a Planck-normalized LCDM model including EDE giving h = 0.728 with those of standard Planck-normalized LCDM with h = 0.678. We find that nonlinear evolution reduces the differences between power spectra of fluctuations at low redshifts. As a result, at z = 0 the halo mass functions on galactic scales are nearly the same, with differences only 1-2%. However, the differences dramatically increase at high redshifts. The EDE model predicts 50% more massive clusters at z = 1 and twice more galaxy-mass halos at z = 4. Even greater increases in abundances of galaxy-mass halos at higher redshifts may make it easier to reionize the universe with EDE. Predicted galaxy abundances and clustering will soon be tested by JWST observations. Positions of baryonic acoustic oscillations (BAOs) and correlation functions differ by about 2% between the models -- an effect that is not washed out by nonlinearities. Both standard LCDM and the EDE model studied here agree well with presently available acoustic-scale observations, but DESI and Euclid measurements will provide stringent new tests.

astro-ph.CO↗

arXiv2020

Building a digital twin of a luminous red galaxy spectroscopic survey: galaxy properties and clustering covariance

Luminous red galaxies (LRGs) are one of the key tracers of the large-scale structure of the Universe used by galaxy surveys. Hence, it is important to make accurate predictions for their properties and clustering, including the errors on these statistics. Here, we describe a novel technique which uses the semi-analytical model of galaxy formation {\sc Galform}, embedded in the high-resolution $N$-body Planck-Millennium simulation, to populate a thousand halo catalogues generated using the Parallel-PM $N$-body {\sc glam} code. Our hybrid scheme allows us to make clustering predictions on scales that cannot be modelled in the original $N$-body simulation. LRGs are selected in the redshift range $z=0.6-1$ from the {\sc Galform} output using similar colour-magnitude cuts in the $r$, $z$ and $W1$ bands to those that will be applied in the Dark Energy Spectroscopic Instrument (DESI) survey. We find that the LRG-halo connection is non-trivial, leading to the prediction of a non-standard halo occupation distribution; in particular, the occupation of central galaxies does not reach unity for the most massive haloes, and drops with increasing mass. The {\sc glam} catalogues reproduce the abundance and clustering of the LRGs predicted by {\sc Galform}, and show good agreement with recent measurements of the clustering of DESI-like LRGs using photometric redshifts. We use the \glam{} mocks to compute the covariance matrices for the two-point correlation function and power spectrum of the LRGs and their background dark matter density field, revealing important differences. We also make predictions for the linear-growth rate and the baryon acoustic oscillations distances at $z=0.6$, $0.74$ and $0.93$. All DESI-like LRG catalogues are made publicly available.

astro-ph.CO↗

arXiv2019

GalWeight Application: A publicly-available catalog of dynamical parameters of 1,800 galaxy clusters from SDSS-DR13, ($\mathtt{GalWCat19}$)

Utilizing the SDSS-DR13 spectroscopic dataset, we create a new publicly-available catalog of 1,800 galaxy clusters (GalWeight cluster catalog, $\mathtt{GalWCat19}$) and a corresponding catalog of 34,471 identified member galaxies. The clusters are identified from overdensities in redshift-phase space. The GalWeight technique introduced in Abdullah, Wilson and Klypin (AWK18) is then applied to identify cluster members. The completeness of the cluster catalog ($\mathtt{GalWCat19}$) and the procedure followed to determine cluster mass are tested on the Bolshoi N-body simulations. The 1,800 $\mathtt{GalWCat19}$ clusters range in redshift between $0.01 - 0.2$ and in mass between $(0.4 - 14) \times 10^{14}h^{-1}M_{\odot}$. The cluster catalog provides a large number of cluster parameters including sky position, redshift, membership, velocity dispersion, and mass at overdensities $Δ= 500, 200, 100, 5.5$. The 34,471 member galaxies are identified within the radius at which the density is 200 times the critical density of the Universe. The galaxy catalog provides the coordinates of each galaxy and the ID of the cluster that the galaxy belongs to. The cluster velocity dispersion scales with mass as $\log(σ_{200})=\log(946\pm52~ \mbox{km} ~ \mbox{s}^{-1}) +(0.349\pm0.142)\log\left[h(z) ~ M_{200}/10^{15}M_\odot\right]$ with scatter of $δ_{\logσ} = 0.06$. The catalogs are publicly available at the following website\footnote{\url{https://mohamed-elhashash-94.webself.net/galwcat/}}.

astro-ph.CO↗