arXiv subjects

Andreas L. Faisst

Publications and source records attributed to Andreas L. Faisst.

At least 73 records · Page 4Linked to original sources

arXiv2025

Mapping the Galaxy Color-Star Formation Rate Relation with Manifold Learning and Infrared Image Stacking

Modern surveys present us with billions of faint galaxies for which we only have broadband images in $\sim$6-8 optical-to-near-infrared (NIR) filters. Galaxy star formation rates (SFRs) are difficult to estimate accurately without spectroscopic diagnostics or far-infrared (FIR) photometry, both of which are prohibitively expensive to obtain for large numbers of faint, high-redshift galaxies. Here we present the empirical relation between SFR and broadband optical-to-NIR colors learned from Spitzer MIPS and Herschel PACS/SPIRE imaging using an innovative stacking analysis that bins galaxies with similar optical-to-NIR spectral energy distributions using a Self-Organizing Map (SOM). Stacking based on optical-to-NIR colors ensures that our FIR stacks are built from galaxies with similar intrinsic physical properties as opposed to stacking simply by stellar mass. We train a 40$\times$40 SOM using 230,638 galaxies selected from the COSMOS field, and stack the mid-to-far infrared images from 24 micron to 500 micron. We are able to measure the median FIR luminosities from half of the SOM cells to calibrate the star formation rate. In addition to investigating the common structures of optical-to-NIR properties and FIR detections labeled on the SOM, we provide calibrated star formation rates for nearly half of the galaxies in the COSMOS fields down to $i-$band magnitude $\leq 25.5$, and present the evolution of the galaxy main sequence for low-mass galaxies to redshift $z\sim2.5$.

astro-ph.GA↗

arXiv2025

Large-Scale Structure in COSMOS-Web: Tracing Galaxy Evolution in the Cosmic Web up to $z \sim 7$ with the Largest JWST Survey

We present a reconstruction of the large-scale structure using the James Webb Space Telescope's (JWST) COSMOS-Web program to trace environmentally driven galaxy evolution up to $z\sim7$. We applied a weighted kernel density estimation method to 160,000 galaxies with robust photometric redshifts. We find that stellar mass has a positive correlation with density at all redshifts, stronger for quiescent galaxies (QGs) at $z\lesssim2.5$, while at higher redshifts ($2.5\lesssim z\lesssim5.5$) this trend is confined to extreme overdense environments, consistent with early mass assembly in proto-clusters. The star-formation rate (SFR) shows a negative trend with density for QGs at $z\lesssim1.2$, reversing at $z\gtrsim1.8$, while star-forming galaxies (SFGs) show a mild positive correlation up to $z\sim5.5$. The specific SFR remains nearly flat for SFGs and declines with density for QGs at $z\lesssim1.2$. Moreover, mass and environmental quenching efficiencies show that mass-driven processes dominate at $z\gtrsim2.5$, the two processes act with comparable strength between $0.8\lesssim z\lesssim2.5$, and environmental quenching becomes stronger for low-mass galaxies ($M_\star\lesssim10^{10} M_\odot$) at $z\lesssim0.8$. These findings reveal that large-scale structure drives galaxy evolution by enhancing early mass assembly in dense regions and increasingly suppressing star formation in low-mass systems at later times, establishing the environmental role of the cosmic web across cosmic history. COSMOS-Web, the largest JWST survey, provides accurate and deep photometric redshifts, reaching 80% mass completeness at $\log(M_\star/M_\odot)\sim8.7$ at $z\sim7$, enabling the first view of how environments shaped galaxy evolution from the epoch of reionization to the present day.

astro-ph.GA↗

arXiv2025

An almost NIRCam-dark dusty star-forming galaxy at z=6.63

We present AC-2168, an almost NIRCam-dark, millimetre-bright galaxy in the COSMOS field. The source was identified blindly in ALMA Band-4 continuum data and remains undetected in the COSMOS-Web DR1 NIRCam catalogue. We spectroscopically confirm a redshift of $z_{\rm spec}=6.631$ from [CII] 158 $μ$m and four tentatively detected CO lines in NOEMA and ALMA data. SED fitting to near-IR to millimetre photometry yields $\rm L_{IR}=1.6\times10^{12}\,L_\odot$, an SFR of $\rm 244\,M_\odot/yr$, heavy dust attenuation $\rm A_V=5.4$ mag, and a stellar mass $\rm M_\star=3.7\times10^{10}\,M_\odot$. From the millimetre continuum and [CII] emission, we infer a warm ISM with $\rm T_{\rm dust}=60K$, $\rm M_{dust}=3.0\times10^{8}\,M_\odot$ and $\rm M_{gas}=4.1\times10^{10}\,M_\odot$. AC-2168 has a gas fraction ($f_{\rm gas}=M_{\rm gas}/(M_\star+M_{\rm gas})$) of $\sim52\%$, a short depletion time of $\rm \sim170Myr$, a compact ($\rm \sim1kpc$) dust-continuum size, and an SFR consistent with the star-forming main sequence at its mass. These properties match expectations for progenitors of massive quiescent galaxies at the peak of their assembly, as implied by NIRSpec-based SFHs of $z\sim4-5$ systems. Using the blind detection, we estimate a space density of $\rm 7.8^{+18.0}_{-6.5}\times10^{-6}\,cMpc^{-3}$ for AC-2168-like NIRCam-dark galaxies at $z\sim6-7$, $\sim42\%$ of the abundance of massive quiescent galaxies at $z\sim4-5$. No overdensity of Ly$α$ emitters or Lyman-break galaxies is found nearby, suggesting AC-2168 does not lie in a prominent protocluster and highlighting the importance of unbiased blind surveys for this population.

astro-ph.GA↗

arXiv2025

COSMOS Spectroscopic Redshift Compilation (First Data Release): 488k Redshifts Encompassing Two Decades of Spectroscopy

We present the COSMOS Spectroscopic Redshift Compilation encompassing ~ 20 years of spectroscopic redshifts within a 10 deg$^2$ area centered on the 2 deg$^2$ COSMOS legacy field. This compilation contains 487,666 redshifts of 266,284 unique objects from 138 individual observing programs up to $z \sim 8$ with median stellar mass $\sim 10^{8.4}$ to $10^{10}$ M$_\odot$ (redshift dependent). Rest-frame $NUVrJ$ colors and SFR -- stellar mass correlations show the compilation primarily contains low- to intermediate-mass star-forming and massive, quiescent galaxies at $z < 1.25$ and mostly low-mass bursty star-forming galaxies at $z > 2$. Sources in the compilation cover a diverse range of environments, including protoclusters such as ``Hyperion''. The full compilation is 50\% spectroscopically complete by $i \sim 23.4$ and $K_s \sim 21.6$ mag; however, this is redshift dependent. Spatially, the compilation is $>50$\% ($>30$\%) complete within the central (outer) region limited to $i < 24$ mag and $K_s < 22.5$ mag, separately. We demonstrate how the compilation can be used to validate photometric redshifts and investigate calibration metrics. By training self-organizing maps on COSMOS2020/Classic and projecting the compilation onto it, we find key galaxy subpopulations that currently lack spectroscopic coverage including $z < 1$ intermediate-mass quiescent galaxies and low-/intermediate-mass bursty star-forming galaxies, $z \sim 2$ massive quiescent galaxies, and $z > 3$ massive star-forming galaxies. This highlights how combining self-organizing maps with our compilation can provide guidance for future spectroscopic observations to get a complete spectroscopic view of galaxy populations. Lastly, the compilation will undergo periodic data releases that incorporate new spectroscopic redshift measurements, providing a lasting legacy resource for the community.

astro-ph.GA↗

arXiv2025

Discovery of a Little Red Dot candidate at $z\gtrsim10$ in COSMOS-Web based on MIRI-NIRCam selection

JWST has revealed a new high-redshift population called little red dots (LRDs). Since LRDs may be in the early phase of black hole growth, identifying them in the early universe is crucial for understanding the formation of the first supermassive black holes. However, no robust LRD candidates have been identified at $z>10$, because commonly-used NIRCam photometry covers wavelengths up to $\sim5\,{\rm μm}$ and is insufficient to capture the characteristic V-shaped spectral energy distributions (SEDs) of LRDs. In this study, we present the first search for $z\gtrsim10$ LRD candidates using both NIRCam and MIRI imaging from COSMOS-Web, which provides the largest joint NIRCam-MIRI coverage to date ($0.20\,{\rm deg^2}$). Taking advantage of MIRI/F770W to remove contaminants, we identify one robust candidate, CW-LRD-z10 at $z_{\rm phot}=10.5^{+0.7}_{-0.6}$ with $M_{\rm UV}=-19.9^{+0.1}_{-0.2}\,{\rm mag}$. CW-LRD-z10 exhibits a compact morphology, a distinct V-shaped SED, and a non-detection in F115W, all consistent with being an LRD at $z\sim10$. Based on this discovery, we place the first constraint on the number density of LRDs at $z\sim10$ with $M_{\rm UV}\sim-20$ of $1.2^{+2.7}_{-1.0}\times10^{-6}\,{\rm Mpc^{-3}\,mag^{-1}}$, suggesting that the fraction of LRDs among the overall galaxy population increases with redshift, reaching $\sim3\%$ at $z\sim10$. Although deep spectroscopy is necessary to confirm the redshift and the nature of CW-LRD-z10, our results imply that LRDs may be a common population at $z>10$, playing a key role in the first supermassive black hole formation.

astro-ph.GA↗

arXiv2025

The ALPINE-CRISTAL-JWST Survey: NIRSpec IFU Data Processing and Spatially-resolved Views of Chemical Enrichment in Normal Galaxies at z=4-6

We present a statistical study of spatially resolved chemical enrichment in 18 main-sequence galaxies at $z=4$--6, observed with \jwst/NIRSpec IFU as part of the ALPINE-CRISTAL-\jwst\ survey. Performing an optimized reduction and calibration procedure, including local background subtraction, light-leakage masking, stripe removal, and astrometry refinement, we achieve robust emission-line mapping on kiloparsec scales. Although line-ratio distributions vary across galaxies in our sample, we generally find mild central enhancements in [O\,\textsc{iii}]/H$β$, [O\,\textsc{ii}]/[O\,\textsc{iii}], [S\,\textsc{ii}]$_{6732}$/[S\,\textsc{ii}]$_{6718}$, H$α$/H$β$, and $L_{\rm Hα}/L_{\rm UV}$, consistent with elevated electron density, dust obscuration, and bursty star formation accompanied by reduced metallicity and ionization parameter. These features point to inside-out growth fueled by recent inflows of pristine gas. Nevertheless, the median metallicity gradient is nearly flat over a few kpc scale, $Δ\log({\rm O/H}) = 0.02 \pm 0.01$ dex kpc$^{-1}$, implying efficient chemical mixing through inflows, outflows, and mergers. From pixel-by-pixel stellar and emission-line characterizations, we further investigate the resolved Fundamental Metallicity Relation (rFMR). Metallicity is described by a fundamental plane with stellar mass and SFR surface densities, but with a stronger dependence on $Σ_{\rm SFR}$ than seen in local galaxies. Our results indicate that the regulatory processes linking star formation, gas flows, and metal enrichment were already vigorous $\sim$1 Gyr after the Big Bang, producing the nearly flat metallicity gradient and a stronger coupling between star formation and metallicity than observed in evolved systems in the local universe.

astro-ph.GA↗

arXiv2025

The Potential of the SPHEREx Mission for Characterizing Polycyclic Aromatic Hydrocarbon 3.3 μm Emission in Nearby Galaxies

Together with gas, stars, and supermassive black holes, dust is crucial in stellar and galaxy evolution. Hence, understanding galaxies' dust properties across cosmic time is critical to studying their evolution. In addition to photometric constraints on the absorption of blue light and its reemission at infrared wavelengths, dust grain properties can be explored spectroscopically via polycyclic aromatic hydrocarbon (PAH) emission bands in the mid-IR. The new SPHEREx space telescope conducts an all-sky spectrophotometric survey of stars and galaxies at wavelengths of 0.75-5$\,μ$m, making it ideal for studying the widespread presence of the 3.3$\,μ$m PAH emission across galaxy populations out to z ~ 0.4. In this paper, we simulated galaxy spectra to investigate SPHEREx's capability to study PAH emission in such galaxies. We find that for the all-sky survey the PAH 3.3$\,μ$m emission band flux can be measured to 30% accuracy at $\log(\rm M/{\rm M_\odot})>9.5$ and star formation rate (SFR) $> 1\,{\rm M_\odot\,yr^{-1}}$ at $z=0.1$, $\log(\rm M/{\rm M_\odot}) > 10.5$ and ${\rm SFR} > 10\,{\rm M_\odot\,yr^{-1}}$ at $z=0.2-0.3$, and $\log(\rm M/{\rm M_\odot})>11$ and ${\rm SFR} > 100\,{\rm M_\odot\,yr^{-1}}$ at $z=0.4$. For deep SPHEREx fields, a factor of ~10 deeper sensitivity limits can be reached. Overall, SPHEREx will enable the measurement of the 3.3$\,μ$m PAH band emission in several hundred thousand galaxies across the sky, providing a population study of the smallest dust grains ("nano grains") and radiation properties in massive galaxies in the nearby Universe.

astro-ph.GA↗

arXiv2025

SCUBADive II: Searching for $z>4$ Dust-Obscured Galaxies via F150W-Dropouts in COSMOS-Web

The relative fraction of obscured galaxies at $z>4$ compared to lower redshifts remains highly uncertain as accurate bookkeeping of the dust-obscured component proves difficult. We address this shortcoming with SCUBADive, a compilation of the JWST counterparts of (sub-)millimeter galaxies in COSMOS-Web, in order to further analyze the distribution and properties of massive dust-obscured galaxies at early times. In this paper, we present a subset of SCUBADive, focusing on 60 ``dark'' galaxies that dropout at 1.5\micron. Motivated by JWST observations of AzTECC71, a far-infrared bright F150W-dropout with $z_{\rm phot}=5.7^{+0.8}_{-0.7}$, we complete a systematic search of F150W-dropouts with SCUBA-2 and ALMA detections to find more candidate high redshift dusty galaxies. Within our subsample, 16 are most similar to AzTECC71 due to fainter F444W magnitudes ($>24$\,mag) and lack of counterparts in COSMOS2020. Despite high star formation rates ($\langle$SFR$\rangle=450^{+920}_{-320}$\,\mdot\,yr$^{-1}$) and large stellar masses ($\langle$log$_{10}$(\mstar)$\rangle=11.2^{+0.5}_{-0.6}$\,\mdot) on average, these galaxies may not be particularly extreme for their presumed epochs according to offsets from the main sequence. We find that heavily obscured galaxies, which would be missed by pre-JWST optical imaging campaigns, comprise $\gtrsim20$\% of galaxies across mass bins and potentially contribute up to 60\% at the very high mass end (log$_{10}$(\mstar/\mdot)$>11.5$) of the $z>4$ stellar mass function.

astro-ph.GA↗

arXiv2025

The ALPINE-CRISTAL-JWST Survey: Revealing Less Massive Black Holes in High-Redshift Galaxies

We present a systematic search for broad-line active galactic nuclei (AGNs) in the ALPINE-CRISTAL-JWST sample of 18 star-forming galaxies ($M_\star>10^{9.5}~M_{\odot}$) at redshifts $z=4.4-5.7$. Using JWST/NIRSpec IFU, we identify 7 AGN candidates through the detection of broad \Ha\ emission lines from 33 aperture spectra centred on photometric peaks. These candidates include one highly robust AGN detection with FWHM $\sim$ 2800 \kms\ and six showing broad components with FWHM $\sim 600-1600$ \kms, with two in a merger system. We highlight that only broad-line detection is effective since these candidates uniformly lie within narrow emission-line ratio diagnostic diagrams where star-forming galaxies and AGNs overlap. The broad-line AGN fraction ranges from 5.9\% to 33\%, depending on the robustness of the candidates. Assuming that the majority are AGNs, the relatively high AGN fraction is likely due to targeting high-mass galaxies, where simulations demonstrate that broad-line detection is more feasible. Their black hole masses range from $10^6$ to $10^{7.5}~M_{\odot}$ with $0.1 \lesssim L_{\rm bol}/L_{\rm Edd}\lesssim 1$. Counter to previous JWST studies at high redshift that found overmassive black holes relative to their host galaxies, our candidates lie close to or below the local $M_{\rm BH}-M_\star$ scaling relations, thus demonstrating the effect of selection biases. This study provides new insights into AGN-host galaxy co-evolution at high redshift by identifying faint broad-line AGNs in galaxy samples, highlighting the importance of considering mass-dependent selection biases and the likelihood of a large population of AGNs being undermassive and just now being tapped by JWST.

astro-ph.GA↗

arXiv2025

Simulating Spectral Confusion in SPHEREx Photometry and Redshifts

We model the impact of source confusion on photometry and the resulting spectrophotometric redshifts for SPHEREx, a NASA Medium-Class Explorer that is carrying out an all-sky near-infrared spectral survey. Spectral confusion from untargeted background galaxies degrades sensitivity and introduces a spectral bias. Using interpolated spectral energy distributions (SEDs) from the COSMOS2020 catalog, we construct a Monte Carlo library of confusion spectra that captures the cumulative impact from faint galaxies. By injecting confusion realizations into galaxy SEDs and performing forced photometry at known source positions, we quantify photometric and redshift error and bias. For our current expected selection of sources for the cosmology analysis, we find typical 1-$σ$ confusion levels range from $0.8-3.8\ μ\mathrm{Jy}$ across $0.75-5.0\ μ\mathrm{m}$. While negligible at full-sky survey depth, spectral confusion becomes significant in the SPHEREx deep fields, reducing the number of intermediate-precision redshifts and inducing a small systematic overestimation in redshift. In parallel, we also model targeted source blending from beam overlaps, which contributes additional photometric noise without systematic redshift bias, provided that positions are known exactly. Together, confusion and blending vary with the depth of the selected reference sample, revealing a trade-off, where deeper selections reduce confusion but increase blending-induced noise. Our methodology informs optimization of the SPHEREx deep-field selection strategy and future treatments of stellar source blending and confusion.

astro-ph.GA↗

arXiv2025

The COSMOS-Web Lens Survey (COWLS) III: forecasts versus data

We compare forecasts for the abundance and properties of strong gravitational lenses in the COSMOS-Web survey, a $0.54$ deg$^2$ survey of the COSMOS field using the NIRCam and MIRI instruments aboard JWST, with the first catalogue of strong lens candidates identified in the observed NIRCam data, COWLS. We modify the lenspop package to produce a forecast for strong lensing in COSMOS-Web. We add a new mock galaxy catalogue to use as the source population, as well as the COSMOS-Web survey specifications, including the transmission data for the four NIRCam filters used. We forecast 107 strong lenses can be detected in COSMOS-Web across all bands, assuming complete subtraction of the lens galaxy light. The majority of the lenses are forecast to have small Einstein radii ($θ_{\rm E} < 1$ arcsecond) and lie at redshifts between $0 < z <2$, whilst the source redshift distribution peaks at $z\sim 3$ and has a long tail extending up to $z \sim 11$, unambiguously showing that strong lensing in JWST can probe the entirety of the epoch of reionisation. We compare our forecast with the distributions of Einstein radii, lens photometric redshifts, and lens and source magnitudes in the observed lenses, finding that whilst the forecast and observed Einstein radii distributions match, the redshifts and magnitudes do not. The observed lens redshift distribution peaks at a slightly lower redshift than the forecast one, whilst the lens magnitudes are systematically brighter in the observed data than in the forecast.

astro-ph.GA↗

arXiv2025

The COSMOS-Web Lens Survey (COWLS) I: Discovery of >100 high redshift strong lenses in contiguous JWST imaging

We present the COSMOS-Web Lens Survey (COWLS), a sample of over 100 strong lens candidates from the $0.54$\,deg$^2$ COSMOS-Web survey, discovered using exquisite James Webb Space Telescope (JWST) imaging across four wavebands. Following two rounds of visual inspection, over 100 candidates were ranked as `high confidence' or `likely' by at least $50\%$ of inspectors. The COWLS sample has several notable properties: (i) magnified source galaxies spanning redshifts $z \sim 0.1$ to $z \sim 9$, which therefore extend into the epoch of reionisation; (ii) the highest-redshift lens galaxies known, pushing galaxy density profile evolution studies beyond $z \sim 2$; (iii) all lenses are distributed within a contiguous $0.54$\,deg$^2$ region, allowing for joint strong and weak lensing analyses; and (iv) a subset exhibits lensed source emission ray-traced near the lens galaxy centers, enabling studies of supermassive black holes and dust absorption. A key innovation of our approach is the use of lens modelling to aid in identifying lenses that may otherwise be missed. This paper is accompanied by the first COWLS public release, providing JWST NIRCam imaging in four bands, lens models, pixelized source reconstructions and lens redshift estimates : https://github.com/Jammy2211/COWLS_COSMOS_Web_Lens_Survey

astro-ph.GA↗

arXiv2025

Understanding the Evolution of Black Hole Accretion and Dust out to z=4 with a Deep Imaging Extragalactic Survey with PRIMA

The cosmic evolution of obscured star formation, dust properties and production mechanisms, and the prevalence of dust-obscured AGN out to high redshifts are currently some of the hot topics in astrophysics. While much progress has been made in the early days with Spitzer and Herschel, these facilities have not reached the necessary depths to observe the mid-IR light of high-redshift (z > 3) galaxies. Recently, the James Webb Space Telescope (JWST) has filled in the blue side of the rest-frame mid-IR. The Atacama Large (Sub)Millimeter Array (ALMA), on the other hand, provides excellent sensitivity in the far-IR regime, allowing the study of dust and gas properties at high redshifts. Filling the wavelength gap between JWST and ALMA is crucial to progress our understanding of early galaxy evolution - and this will be an important goal in the next decades. The Probe far-IR Mission for Astrophysics (PRIMA), with sensitive imaging and spectroscopic capabilities at 24-240$μ$m and currently in Phase A study, will achieve this and provide insights into early galaxy evolution, Black Hole growth, and dust production mechanisms. Here we present PRIDES, a possible deep and wide-area survey over 1.6 square-degrees of the COSMOS field with PRIMA to study these science cases.

astro-ph.GA↗

arXiv2025

Physical properties of galaxies and the UV Luminosity Function from $z\sim6$ to $z\sim14$ in COSMOS-Web

We present measurements of the rest-frame ultraviolet luminosity function (UVLF) in three redshift bins over $z\sim5.5$-14 from the JWST COSMOS-Web survey. Our samples, selected using the dropout technique in the HST/ACS F814W, JWST/NIRCam F115W, and F150W filters, contain a total of 3099 galaxies spanning a wide luminosity range from faint ($M_{\rm UV}\sim-19$ mag) to bright ($M_{\rm UV}\sim-22.5$ mag). The galaxies are undergoing rapid star formation, with blue stellar populations. Surprisingly, their median UV spectral slope $β$ does not evolve at $z>8$, suggesting minimal dust, or physical separation of dust and star formation at early epochs. The measured UVLF exhibits an excess at the bright-end ($M_{\rm UV}<-21$ mag) compared to pre-JWST empirical results and theoretical predictions of an evolving Schechter function, with the excess beginning at $z\sim9$ and becoming increasingly prominent toward $z\sim12$. Our analysis suggests that reproducing the observed abundance of UV-bright galaxies at high redshift requires a combination of physical processes, including elevated star formation efficiencies, moderate levels of stochasticity in galaxy luminosities, and minimal dust attenuation.

astro-ph.GA↗

arXiv2025

Gas-Poor Hosts and Gas-Rich Companions of $z\approx$3.5 Radio Active Galactic Nuclei: ALMA Insights into Jet Triggering and Feedback

Cold gaseous systems play important roles in galaxy evolution by possibly providing fuel to ignite active galactic nuclei (AGN) activity and star-formation. In this work, we analyze [CII]$158\rm μm$ and continuum observations from ALMA for a sample of four radio AGN at $z \approx 3.5$, focusing on eight associated companion cloud systems discovered within projected distances of tens of kiloparsecs or less. The spatial distribution of these companions indicates that the majority of cold gas is not located at the AGN position, i.e., not in their host galaxies. With the assistance of [CII] at $0.2"$ resolution, we further confirm the gas-poor nature of the hosts by re-analyzing archival [CI] (a tracer of H$_{2}$) at $\sim2"$ resolution. Our sample has [CII] luminosities in a range of $2.8\times10^{8}<L_{\rm [CII]}/L_{\odot}<4.2\times10^{9}$. The $L_{\rm [CII]}/L_{\rm IR}$ ratio, $\sim 9.4\times10^{-4}$, is consistent with sources discussed in the literature. Our findings show the gas-poor radio AGN hosts have nearby gas-rich companions. We propose that these companions may be stripped clouds resulting from merger processes, which could be a trigger of radio-loud AGN. They may also be a signature of negative AGN feedback (e.g., shock heating) on these infalling companions and on the host galaxy. In general, our analysis shows that powerful AGN at and before Cosmic Noon are impacting and being impacted by cold gaseous clouds in their circumgalactic or protointracluster media.

astro-ph.GA↗

arXiv2025

Chemical Abundances of Early Quiescent Galaxies: New Observations and Modelling Impacts

Recent stellar chemical abundance measurements of a handful of $z\sim2$ quiescent galaxies have suggested these galaxies exhibit a remarkably strong $α$-enhancement compared to their local and intermediate redshift counterparts. This apparent chemical evolution following quenching suggests that even the innermost regions of massive early-type galaxies may have experienced substantial mixing of stars in mergers, challenging a purely inside-out growth model. However, larger samples are needed to determine whether a high $α$-enhancement ([Mg/Fe] $\approx 0.5$) is common in $z \sim 2$ quiescent galaxies, and a comparative analysis is needed to determine whether it is consistently inferred using different stellar population synthesis models. We report age and stellar chemical abundance measurements for a sample of four gravitationally lensed quiescent galaxies at $z\sim2.1-2.65$ based on Magellan/FIRE spectroscopy. For three of these galaxies we constrain the $α$-enhancement, and in two cases we measure high values comparable to earlier results when the spectra are analyzed consistently. We also find that the choice of modeling approach can exert a significant effect on the measured abundances. This model dependence can be partly, but not entirely, explained by the complex abundance patterns of $α$ elements in galaxies, which has been observed at lower redshifts and in one $z \sim 2$ quiescent galaxy. Our investigation highlights the importance of independently varying abundance of $α$ elements when fitting the spectra of such galaxies. Observations with JWST will soon deliver precise and spatially resolved abundances of these and other quiescent galaxies at cosmic noon, opening a new window into their evolution.

astro-ph.GA↗

arXiv2025

The COSMOS-Web deep galaxy group catalog up to $z=3.7$

Galaxy groups with $M_{tot} \lesssim 10^{14}$ $M_\odot$ and up to a few tens of members are the most common galaxy environment, marking the transition between field and massive clusters. Identifying groups plays a crucial role in understanding structure formation and galaxy evolution. Modern deep surveys allow us to build well-characterized samples of groups up to the regime where structures were taking shape. We aimed to build the largest deep catalog of galaxy groups to date over the COSMOS-Web field effective area of 0.45 deg$^2$, leveraging the deep high quality data of the new COSMOS-Web photometric catalog resulted from the James Webb Space Telescope observations of the COSMOS-Web field. We performed the group search with the AMICO algorithm, a linear matched filter based on an analytical model for the group signal. AMICO has already been tested in wide and deep field surveys, including COSMOS data up to $z=2$. In this work, we tested the algorithm performances at even higher redshift and searched for protocluster cores at $z>2$. We compiled a list of known protoclusters in COSMOS at $2 \leq z \leq 3.7$, matched them with our detections and studied the clustering of the detected cores. We estimated purity and completeness of our sample by creating data-driven mocks with the SinFoniA code and linked signal-to-noise to purity. We detected 1678 groups in the COSMOS-Web field up to $z=3.7$, including lists of members extending nearly two magnitudes deeper than the previous AMICO-COSMOS catalog. 756 groups were detected with purity of 80\%. More than 500 groups have their redshift confirmed by assigning spectroscopic counterparts. This group catalog offers a unique opportunity to explore galaxy evolution in different environments spanning $\sim$12 Gyr and to study groups, from the least rich population to the formation of the most massive clusters.

astro-ph.GA↗

arXiv2025

COSMOS-Web: Comprehensive Data Reduction for Wide-Area JWST NIRCam Imaging

We present the data reduction methodology used for the COSMOS-Web survey JWST NIRCam data. Covering 0.54 deg^2 with four broadband filters (F115W, F150W, F277W, F444W) and a total exposure time of approximately 270 hours, COSMOS-Web represents the largest contiguous field surveyed during JWST Cycle 1, posing unique data reduction challenges due to its extensive scale. By combining the official JWST Calibration Pipeline with custom improvements for noise removal, background subtraction, and astrometric alignment, we achieve high fidelity science-ready mosaics. We detail the systematic approach employed in the three stages of the JWST Calibration Pipeline. The data, collected in three epochs from January 2023 to January 2024, encompass 152 visits and have been processed into 20 mosaic tiles to optimize computational efficiency and data processing. The final data products achieve 5 sigma depths of 26.7-28.3 AB mag in 0.15" apertures. The processed and calibrated datasets are made available to the public.

astro-ph.IM↗