Red Galaxies Research Articles

Redshift evolution and covariances for joint lensing and clustering studies with DESI Y1

ABSTRACT Galaxy–galaxy lensing (GGL) and clustering measurements from the Dark Energy Spectroscopic Instrument Year 1 (DESI Y1) data set promise to yield unprecedented combined-probe tests of cosmology and the galaxy–halo connection. In such analyses, it is essential to identify and characterize all relevant statistical and systematic errors. We forecast the covariances of DESI Y1 GGL + clustering measurements and the systematic bias due to redshift evolution in the lens samples. Focusing on the projected clustering and GGL correlations, we compute a Gaussian analytical covariance, using a suite of N-body and lognormal simulations to characterize the effect of the survey footprint. Using the DESI one percent survey data, we measure the evolution of galaxy bias parameters for the DESI luminous red galaxy (LRG) and bright galaxy survey (BGS) samples. We find mild evolution in the LRGs in $0.4 < z < 0.8$, subdominant to the expected statistical errors. For BGS, we find less evolution for brighter absolute magnitude cuts, at the cost of reduced sample size. We find that for a redshift bin width $\Delta z = 0.1$, evolution effects on DESI Y1 GGL is negligible across all scales, all fiducial selection cuts, all fiducial redshift bins. Galaxy clustering is more sensitive to evolution due to the bias squared scaling. Nevertheless the redshift evolution effect is insignificant for clustering above the 1-halo scale of $0.1h^{-1}$ Mpc. For studies that wish to reliably access smaller scales, additional treatment of redshift evolution is likely needed. This study serves as a reference for GGL and clustering studies using the DESI Y1 sample.

Mapping the oxygen abundance in Red Geysers and its relation with the gas kinematics using megacubes

ABSTRACT Red Geysers are galaxies with low-star formation rates and galactic scale ionized outflows likely driven by low-luminosity active galactic nuclei (AGN). We investigated the impact of AGN winds on the oxygen abundance using integral field spectroscopic data from Mapping Nearby Galaxies for Red Geysers, control galaxies (quiescent galaxies without outflows), and AGN hosts within the inner 1.5 kpc radius. Red Geyser galaxies have higher W$_{80}$ values compared to those of AGN and controls, with 64 per cent showing W$_{80}\gt 500$ km s$^{-1}$ that is indicative of outflow. Only 40 per cent of controls and 31 per cent of AGNs reach this value. We found a small tendency of the oxygen abundance distribution of controls to be biased towards higher values than those of Red Geysers. However, Red Geysers do not show a correlation between H$\alpha$ width (parametrized by the W$_{\rm 80}$) and oxygen abundance, which indicates that AGN winds are not significantly impacting the chemical abundance of the nuclear region of these galaxies. The oxygen abundance distribution mean value for the tree samples is $\rm 12+log(O/H)\sim$8.7 ($\mathit{Z}\sim \rm Z_{\odot })$. On the other hand, AGN hosts show a positive correlation between W$_{80}$ and O/H which could be due to star formation that outflows from the active nuclei could induce; or to the reservoir of gas that makes the nucleus active, and its is also used in the star formation.

The Early Data Release of the Dark Energy Spectroscopic Instrument

The Dark Energy Spectroscopic Instrument (DESI) completed its 5 month Survey Validation in 2021 May. Spectra of stellar and extragalactic targets from Survey Validation constitute the first major data sample from the DESI survey. This paper describes the public release of those spectra, the catalogs of derived properties, and the intermediate data products. In total, the public release includes good-quality spectral information from 466,447 objects targeted as part of the Milky Way Survey, 428,758 as part of the Bright Galaxy Survey, 227,318 as part of the Luminous Red Galaxy sample, 437,664 as part of the Emission Line Galaxy sample, and 76,079 as part of the Quasar sample. In addition, the release includes spectral information from 137,148 objects that expand the scope beyond the primary samples as part of a series of secondary programs. Here, we describe the spectral data, data quality, data products, Large-Scale Structure science catalogs, access to the data, and references that provide relevant background to using these spectra.

Age of Massive Galaxies at Redshift 8

Recent James Webb Space Telescope data analyses have shown that massive red galaxies existed at redshifts z ≳ 6, a discovery that is difficult to understand in the context of standard cosmology (ΛCDM). Here, we analyze these observations more deeply, by fitting a stellar population model to the optical and near-infrared photometric data. These fits include a main stellar population in addition to a residual younger population and with the same extinction for both (a lower extinction for the younger population is unphysical). Extra stellar populations or the inclusion of an active galactic nucleus component do not significantly improve the fits. These galaxies are being viewed at very high redshifts, with an average 〈z〉 ≈ 8.2, when the ΛCDM Universe was only ≈600 Myr old. This result conflicts with the inferred ages of these galaxies, however, which were on average between 0.9 and 2.4 Gyr old within a 95% confidence level. Given the sequence of star formation and galaxy assembly in the standard model, these galaxies should instead be even younger than 290 Myr on average, for which our analysis assigns a probability of only <3 × 10−4 (≳3.6σ tension). This outcome may indicate the need to consider nonstandard cosmologies. Nevertheless, our conclusions result from several approximations in stellar astrophysics and extinction, so they should be taken with a grain of salt. Further research is necessary to corroborate the possible existence of galaxies older than the ΛCDM Universe at their observed redshifts.

Galaxy–Galaxy Lensing Data: f(T) Gravity Challenges General Relativity

We use galaxy–galaxy lensing data to test general relativity and f(T) gravity at galaxy scales. We consider an exact spherically symmetric solution of f(T) theory, which is obtained from an approximate quadratic correction, and thus it is expected to hold for every realistic deviation from general relativity. Quantifying the deviation by a single parameter Q, and following the post-Newtonian approximation, we obtain the corresponding deviation in the gravitational potential, shear component, and effective excess surface density profile. We used five stellar mass samples and divided them into blue and red galaxies to test the model dependence on galaxy color, and we modeled the excess surface density profiles using the Navarro–Frenk–White profiles. Based on the group catalog from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) we finally extract Q=−2.138−0.516+0.952×10−5 Mpc−2 at 1σ confidence. This result indicates that f(T) corrections on top of general relativity are favored. Finally, we apply information criteria, such as the Akaike and Bayesian ones, and although the dependence of f(T) gravity on the off-center effect implies that its optimality needs to be carefully studied, our analysis shows that f(T) gravity is more efficient in fitting the data compared to general relativity and the ΛCDM paradigm, and thus it offers a challenge to the latter.

The cosmic microwave background lensing imprint of cosmic voids detected in the WISE-Pan-STARRS luminous red galaxy catalog

The cross-correlation of cosmic voids with the lensing convergence (kappa ) map of cosmic microwave background (CMB) fluctuations offers a powerful tool with which to refine our understanding of the dark sector in the consensus cosmological model. Our principal aim is to compare the lensing signature of our galaxy dataset with simulations based on the concordance model and to characterize the results with an $A_ kappa $ consistency parameter normalized to unity. In particular, our measurements contribute to the understanding of the “lensing-is-low” tension of the Lambda CDM model. In this analysis, we selected luminous red galaxies (LRGs) from the WISE- Pan-STARRS dataset, enabling an extended cross-correlation measurement using a 14,200 deg$^2$ sky area, which offers a more precise measurement than previous studies. We created 2D and 3D void catalogs to cross-correlate their locations with the Planck CMB lensing map and studied their average imprint signal using a stacking methodology. Applying the same procedure, we also generated a mock galaxy catalog from the WebSky simulation to serve as a basis for comparison. The 2D void analysis reveals a good agreement with the standard cosmological model, with $A_ kappa 0.08$ amplitude; that is, $S/N=13.3$, showing a higher signal-to-noise than previous studies using voids detected in the Dark Energy Survey (DES) dataset. The 3D void analysis exhibited a lower signal-to-noise ratio and demonstrated worse agreement with our mock catalog than the 2D voids. These deviations might be attributed to limitations in the mock catalog, such as imperfections in the LRG selection, as well as a potential asymmetry between the northern and southern patches of the Pan-STARRS dataset in terms of data quality. Overall, we present a significant detection of a CMB lensing signal associated with cosmic voids, largely consistent with the concordance model. Future analyses using even larger datasets also hold great promise of further sharpening these results, given their complementary nature to large-scale structure analyses.

The Uchuu-glam BOSS and eBOSS LRG lightcones: exploring clustering and covariance errors

ABSTRACT 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 UchuuN-body simulation, employing SHAM technique to assign LRG to (sub)haloes, and (ii) 16 000 covariance lightcones from GLAM-UchuuN-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 per cent and 60 per cent. 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 large-scale structure (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.

A multitracer analysis for the eBOSS galaxy sample based on the effective field theory of large-scale structure

ABSTRACT We perform a multitracer full-shape analysis in Fourier space based on the effective field theory of large-scale structure (EFTofLSS) using the complete Sloan Digital Sky Survey IV (SDSS-IV) extended Baryon Oscillation Spectroscopic Survey (eBOSS) DR16 luminous red galaxy (LRG) and emission line galaxy (ELG) samples. We study in detail the impact of the volume projection effect and different prior choices when doing the full-shape analysis based on the EFTofLSS model. We show that adopting a combination of Jeffreys prior and Gaussian prior can mitigate the volume effect and avoid exploring unphysical regions in the parameter space at the same time, which is crucial when jointly analysing the eBOSS LRG and ELG samples. We validate our pipeline using 1000 eBOSS EZmocks. By performing a multitracer analysis on mocks with comparable footprints, we find that cosmological constraints can be improved by $\sim 10-35~{{\ \rm per\ cent}}$ depending on whether we assume zero stochastic terms in the cross power spectrum, which breaks the degeneracy and boosts the constraints on the standard deviation of matter density fluctuation σ8. Combining with the Big Bang Nucleosynthesis (BBN) prior and fixing the spectral tilt ns to Planck value, our multitracer full-shape analysis measures H0 = 70.0 ± 2.3 km s−1Mpc−1, $\Omega _m=0.317^{+0.017}_{-0.021}$, $\sigma _8=0.787_{-0.062}^{+0.055}$, and $S_8=0.809_{-0.078}^{+0.064}$, consistent with the Planck 2018 results. In particular, the constraint on σ8 is improved beyond that obtained from the single tracer analysis by 18 per cent, or by 27 per cent when assuming zero stochastic terms in the cross power spectrum.

Bayesian inference methodology for primordial power spectrum reconstructions from Large Scale Structure

We use Bayesian inference to develop a non-parametric method to reconstruct the primordial power spectrum Pℛ (k) from Large Scale Structure (LSS) data. The performance of the method is assessed by testing it against simulations of the clustering of high-z (QSOs) objects. Their clustering is derived from different templates of the primordial power spectrum motivated by models of inflation: the Standard Model power law characterized by the two parameters As and ns ; a local feature template; and a global oscillatory template. The primordial power spectrum is reconstructed using N knots in the log {k, Pℛ (k)} plane while sampling the cosmological parameters {H 0, Ω b , Ω c }. We use two statistical tests to examine the reconstructions for signs of primordial features: a global test comparing the evidences and a novel local test quantifying the power of the hypothesis test between the power law model and the marginalized probability over N model. We also discuss results of an application to low-z (ELGs) objects with two different photometric errors keeping the cosmology fixed. The method shows good performance in all scenarios considered. In particular, the tests show no feature detection for the standard power-law primordial power spectrum; yet, the method is able to detect power spectrum deviations at a percent level for all considered features, combining either the low-z or the high-z redshift bins. In addition, we include a test proof-of-concept application to real data from the Sloan Digital Sky Survey Luminous Red Galaxy Data Release 4 (SDSS LRG 04), finding no preference for deviations from the primordial power law. The method is flexible, model independent, and suitable for its application to existing and future LSS surveys.

When, where, and how star formation happens in a galaxy pair at cosmic noon using CANUCS JWST/NIRISS grism spectroscopy

ABSTRACT Spatially resolved studies are key to understanding when, where, and how stars form within galaxies. Using slitless grism spectra and broad-band imaging from the CAnadian NIRISS Unbiased Cluster Survey (CANUCS), we study the spatially resolved properties of a strongly lensed (μ = 5.4$\pm$1.8) z = 0.8718 galaxy pair consisting of a blue face-on galaxy (10.2 $\pm$ 0.2 log($M/M_\odot$)) with multiple star-forming clumps and a dusty red edge-on galaxy (9.9 $\pm$ 0.3 log($M/M_\odot$)). We produce accurate H $\alpha$ maps from JWST/NIRISS grism data using a new methodology that accurately models spatially varying continuum and emission line strengths. With spatially resolved indicators, we probe star formation on time-scales of $\sim$10 Myr (NIRISS H $\alpha$ emission line maps) and $\sim$100 Myr (UV imaging and broad-band SED fits). Taking the ratio of the H $\alpha$ to UV flux ($\eta$), we measure spatially resolved star formation burstiness. We find that in the face-on galaxy both H $\alpha$ and broad-band star formation rates (SFRs) drop at large galactocentric radii by a factor of $\sim$4.7 and 3.8, respectively, while SFR over the last $\sim$100 Myrs has increased by a factor of 1.6. Additionally, of the 20 clumps identified in the galaxy pair we find that 7 are experiencing bursty star formation, while 10 clumps are quenching, and 3 are in equilibrium (either being in a state of steady star formation or post-burst). Our analysis reveals that the blue face-on galaxy disc is predominantly in a quenching or equilibrium phase. However, the most intense quenching within the galaxy is seen in the quenching clumps. This pilot study demonstrates what JWST/NIRISS data can reveal about spatially varying star formation in galaxies at Cosmic Noon.

DESI complete calibration of the colour–redshift relation (DC3R2): results from early DESI data

ABSTRACT We present initial results from the Dark Energy Spectroscopic Instrument (DESI) complete calibration of the colour–redshift relation (DC3R2) secondary target survey. Our analysis uses 230 k galaxies that overlap with KiDS-VIKING ugriZYJHKs photometry to calibrate the colour–redshift relation and to inform photometric redshift (photo-z) inference methods of future weak lensing surveys. Together with emission line galaxies (ELGs), luminous red galaxies (LRGs), and the Bright Galaxy Survey (BGS) that provide samples of complementary colour, the DC3R2 targets help DESI to span 56 per cent of the colour space visible to Euclid and LSST with high confidence spectroscopic redshifts. The effects of spectroscopic completeness and quality are explored, as well as systematic uncertainties introduced with the use of common Self-Organizing Maps trained on different photometry than the analysis sample. We further examine the dependence of redshift on magnitude at fixed colour, important for the use of bright galaxy spectra to calibrate redshifts in a fainter photometric galaxy sample. We find that noise in the KiDS-VIKING photometry introduces a dominant, apparent magnitude dependence of redshift at fixed colour, which indicates a need for carefully chosen deep drilling fields, and survey simulation to model this effect for future weak lensing surveys.

Correction to: The H i content of red geyser galaxies

Correction to: The H <scp>i</scp> content of red geyser galaxies

Local primordial non-Gaussianity from the large-scale clustering of photometric DESI luminous red galaxies

ABSTRACT We use angular clustering of luminous red galaxies from the Dark Energy Spectroscopic Instrument (DESI) imaging surveys to constrain the local primordial non-Gaussianity parameter fNL. Our sample comprises over 12 million targets, covering 14 000 deg2 of the sky, with redshifts in the range 0.2 &amp;lt; z &amp;lt; 1.35. We identify Galactic extinction, survey depth, and astronomical seeing as the primary sources of systematic error, and employ linear regression and artificial neural networks to alleviate non-cosmological excess clustering on large scales. Our methods are tested against simulations with and without fNL and systematics, showing superior performance of the neural network treatment. The neural network with a set of nine imaging property maps passes our systematic null test criteria, and is chosen as the fiducial treatment. Assuming the universality relation, we find $f_{\rm NL} = 34^{+24(+50)}_{-44(-73)}$ at 68 per cent (95 per cent) confidence. We apply a series of robustness tests (e.g. cuts on imaging, declination, or scales used) that show consistency in the obtained constraints. We study how the regression method biases the measured angular power spectrum and degrades the fNL constraining power. The use of the nine maps more than doubles the uncertainty compared to using only the three primary maps in the regression. Our results thus motivate the development of more efficient methods that avoid overcorrection, protect large-scale clustering information, and preserve constraining power. Additionally, our results encourage further studies of fNL with DESI spectroscopic samples, where the inclusion of 3D clustering modes should help separate imaging systematics and lessen the degradation in the fNL uncertainty.

Repainting the colour–mass diagrams by unearthing the green mountain: dust-rich S0 galaxies in the colour–(galaxy stellar mass) diagram, and the colour–(black hole mass) relations for dust-poor versus dust-rich galaxies

ABSTRACT Lenticular galaxies are notoriously misclassified as elliptical galaxies and, as such, a (disc inclination)-dependent correction for dust is often not applied to the magnitudes of dusty lenticular galaxies. This results in overly red galaxy colours, impacting their distribution in the colour–magnitude diagram. It is revealed how this has led to an underpopulation of the ‘green valley’ by hiding a ‘green mountain’ of massive dust-rich lenticular galaxies – known to be built from gas-rich major mergers – within the ‘red sequence’ of colour–(stellar mass) diagrams. Correcting for dust, a ‘green mountain’ appears at M*,gal ∼ 1011 M⊙, along with signs of an extension to lower masses producing a ‘green range’ or ‘green ridge’ on the green side of the ‘red sequence’ and ‘blue cloud.’ The ‘red sequence’ is shown to be comprised of two components: a red plateau defined by elliptical galaxies with a near-constant colour and by lower-mass dust-poor lenticular galaxies, which are mostly a primordial population but may include faded/transformed spiral galaxies. The presence of the quasi-triangular-shaped galaxy evolution sequence, previously called the ‘Triangal’, is revealed in the galaxy colour–(stellar mass) diagram. It tracks the speciation of galaxies and their associated migration through the diagram. The connection of the ‘Triangal’ to previous galaxy morphology sequences (Fork, Trident, and Comb) is also shown herein. Finally, the colour–(black hole mass) diagram is revisited, revealing how the dust correction generates a blue–green sequence for the spiral and dust-rich lenticular galaxies that is offset from a green–red sequence defined by the dust-poor lenticular and elliptical galaxies.

Atomic hydrogen shows its true colours: correlations between H i and galaxy colour in simulations

ABSTRACT Intensity mapping experiments are beginning to measure the spatial distribution of neutral atomic hydrogen H i to constrain cosmological parameters and the large-scale distribution of matter. However, models of the behaviour of H i as a tracer of matter are complicated by galaxy evolution. In this work, we examine the clustering of H i in relation to galaxy colour, stellar mass, and H i mass in IllustrisTNG at z = 0, 0.5, and 1. We compare the H i-red and H i-blue galaxy cross-power spectra, finding that H i-red has an amplitude 1.5 times greater than H i-blue at large scales. The cross-power spectra intersect at ≈3 Mpc in real space and ≈10 Mpc in redshift space, consistent with z ≈ 0 observations. We show that H i clustering increases with galaxy H i mass and depends weakly on detection limits in the range MH i ≤ 108 M⊙. In terms of M⋆, we find massive blue galaxies cluster more than less massive ones. Massive red galaxies, however, cluster the weakest amongst red galaxies. These opposing trends arise from central-satellite compositions. Despite these M⋆ trends, we find that the cross-power spectra are largely insensitive to detection limits in galaxy surveys. Counter-intuitively, all auto and cross-power spectra for red and blue galaxies and H i decrease with time at all scales. We demonstrate that processes associated with quenching contribute to this trend. The complex interplay between H i and galaxies underscores the importance of understanding baryonic effects when interpreting the large-scale clustering of H i, blue, and red galaxies at z ≤ 1.

Cosmological constraints on early dark energy from the full shape analysis of eBOSS DR16

ABSTRACT We evaluate the effectiveness of early dark energy (EDE) in addressing the Hubble tension using the luminous red galaxy (LRG), quasar (QSO), and emission line galaxy (ELG) samples from the completed eBOSS survey. We perform cosmological parameter measurements based on full shape analysis of the power spectrum employing the effective field theory of large-scale structure (EFTofLSS). EDE is known to strongly suffer from volume projection effects, complicating cosmological constraints’ interpretation. To quantify the volume projection effects within an EDE full shape analysis, we explore the impact of different prior choices on the nuisance parameters of EFTofLSS through an extensive mock study. We compare classical Gaussian priors to the non-informative Jeffreys prior, known to mitigate volume projection effects in ΛCDM. Our full shape analysis combines eBOSS and BOSS data with Planck, external Baryon Acoustic Oscillation (BAO), PantheonPlus, and SH0ES supernova data. EDE reduces the tension from 5.2σ to 3σ compared to ΛCDM, yielding $H_0=71.73_{-0.86}^{+0.82}$ km s−1 Mpc−1 with $f_\mathrm{EDE} = 0.1179_{-0.022}^{+0.025}$ (Gaussian priors) and $H_0=72.03_{-0.87}^{+0.82}$ km s−1 Mpc−1 with $f_\mathrm{EDE} = 0.1399_{-0.022}^{+0.023}$ (Jeffreys prior). Although the Hubble tension is mitigated compared to ΛCDM, the inclusion of eBOSS data amplifies the tension within EDE from 2σ to 3σ, in contrast to the full shape analysis of BOSS data with Planck, external BAO, PantheonPlus, and SH0ES. This highlights the significance of incorporating additional large-scale structure data in discussions concerning models aiming to resolve the Hubble tension.

The DESI one-per cent survey: exploring the halo occupation distribution of luminous red galaxies and quasi-stellar objects with AbacusSummit

ABSTRACT We present the first comprehensive halo occupation distribution (HOD) analysis of the Dark Energy Spectroscopic Instrument (DESI) One-Percent Survey luminous red galaxy (LRG) and Quasi Stellar Object (QSO) samples. We constrain the HOD of each sample and test possible HOD extensions by fitting the redshift-space galaxy 2-point correlation functions in 0.15 &amp;lt; r &amp;lt; 32 h−1 Mpc in a set of fiducial redshift bins. We use AbacusSummit cubic boxes at Planck 2018 cosmology as model templates and forward model galaxy clustering with the AbacusHOD package. We achieve good fits with a standard HOD model with velocity bias, and we find no evidence for galaxy assembly bias or satellite profile modulation at the current level of statistical uncertainty. For LRGs in 0.4 &amp;lt; z &amp;lt; 0.6, we infer a satellite fraction of $f_\mathrm{sat} = 11\pm 1~{y{\ \mathrm{per\,cent}}}$, a mean halo mass of $\log _{10}\overline{M}_h/M_\odot =13.40^{+0.02}_{-0.02}$, and a linear bias of $b_\mathrm{lin} = 1.93_{-0.04}^{+0.06}$. For LRGs in 0.6 &amp;lt; z &amp;lt; 0.8, we find $f_\mathrm{sat}=14\pm 1~{{\ \mathrm{per\,cent}}}$, $\log _{10}\overline{M}_h/M_\odot =13.24^{+0.02}_{-0.02}$, and $b_\mathrm{lin}=2.08_{-0.03}^{+0.03}$. For QSOs, we infer $f_\mathrm{sat}=3^{+8}_{-2}\mathrm{per\,cent}$, $\log _{10}\overline{M}_h/M_\odot = 12.65^{+0.09}_{-0.04}$, and $b_\mathrm{lin} = 2.63_{-0.26}^{+0.37}$ in redshift range 0.8 &amp;lt; z &amp;lt; 2.1. Using these fits, we generate a large suite of high fidelity galaxy mocks, forming the basis of systematic tests for DESI Y1 cosmological analyses. We also study the redshift-evolution of the DESI LRG sample from z = 0.4 up to z = 1.1, revealling significant and interesting trends in mean halo mass, linear bias, and satellite fraction.

The UV continuum slopes of early star-forming galaxies in JADES

ABSTRACT The power-law slope of the rest-ultraviolet (UV) continuum (fλ ∝ λβ) is a key metric of early star-forming galaxies, providing one of our only windows into the stellar populations and physical conditions of z ≳ 10 galaxies. Expanding upon previous studies with limited sample sizes, we leverage deep imaging from the JWST Advanced Deep Extragalactic Survey (JADES) to investigate the UV slopes of 179 z ≳ 9 galaxies with apparent magnitudes of mF200W ≃ 26–31, which display a median UV slope of β = −2.4. We compare to a statistical sample of z ≃ 5–9 galaxies, finding a shift towards bluer rest-UV colours at all $M_{\rm UV}$. The most UV-luminous z ≳ 9 galaxies are significantly bluer than their lower redshift counterparts, representing a dearth of moderately red galaxies within the first 500 Myr. At yet earlier times, the z ≳ 11 galaxy population exhibits very blue UV slopes, implying very low impact from dust attenuation. We identify a robust sample of 44 galaxies with β ≲ −2.8, which have spectral energy distributions requiring models of density-bounded H ii regions and median ionizing photon escape fractions of 0.51 to reproduce. Their rest-optical colours imply that this sample has weaker emission lines (median mF356W − mF444W = 0.19 mag) than typical galaxies (median mF356W − mF444W = 0.39 mag), consistent with the inferred escape fractions. This sample consists of relatively low stellar masses (median $\log (M/{\rm M}_{\odot })=7.5\pm 0.2$), and specific star formation rates (sSFRs; median $=79 \, \rm Gyr^{-1}$) nearly twice that of our full galaxy sample (median sSFRs $=44 \, \rm Gyr^{-1}$), suggesting these objects are more common among systems experiencing a recent upturn in star formation. We demonstrate that the shutoff of star formation provides an alternative solution for modelling of extremely blue UV colours, making distinct predictions for the rest-optical emission of these galaxies. Future spectroscopy will be required to distinguish between these physical pictures.

Quantifying the Tension between Cosmological Models and JWST Red Candidate Massive Galaxies

We develop a Python tool to estimate the tail distribution of the number of dark matter halos beyond a mass threshold and in a given volume in a light-cone. The code is based on the extended Press–Schechter model and is computationally efficient, typically taking a few seconds on a personal laptop for a given set of cosmological parameters. The high efficiency of the code allows a quick estimation of the tension between cosmological models and the red candidate massive galaxies released by the James Webb Space Telescope, as well as scanning the theory space with the Markov Chain Monte Carlo method. As an example application, we use the tool to study the cosmological implication of the candidate galaxies presented in Labbé et al. The standard Λ cold dark matter (ΛCDM) model is well consistent with the data if the star formation efficiency can reach ∼0.3 at high redshift. For a low star formation efficiency ϵ ∼ 0.1, the ΛCDM model is disfavored at ∼2σ–3σ confidence level.

Lopsided Galaxy Distributions in Massive TNG300 Clusters

Studies of isolated central galaxies and their satellites have shown that the spatial distributions of the satellites are distinctly “lopsided” with respect to the locations of the central galaxies. Here we extend this type of analysis to larger systems by analyzing the lopsidedness of 280 massive galaxy clusters in the IllustrisTNG300 Λ Cold Dark Matter simulation. Using a pairwise clustering statistic, we compute the probability that pairs of cluster galaxies are separated by a given polar angle difference, Δϕ, in the plane of the sky. Relative to the location of the central cluster galaxy, we find a statistically significant excess of galaxy pairs that are located on the same side of the cluster. The lopsidedness of the galaxy distribution is most pronounced for large clusters and for pairs of intrinsically red galaxies. The results summarized here were presented at the 243rd meeting of the American Astronomical Society.