Sedona H. Price

At low redshift, massive quiescent galaxies (MQGs) are most frequently found in massive, rich galaxy clusters, but at high redshift the trend is less clear. Here, we present spectroscopic evidence of the effects of environment on the formation and assembly of high-redshift MQGs. We identify 26 (9) log ( M * / M ⊙ ) ≥ 10.5 ( 10.0 ≤ log ( M * / M ⊙ ) < 10.5 ) spectroscopically confirmed quiescent galaxies in the UDS and EGS fields at 3 < z < 5 with NIRSpec spectroscopy from the Red Unknowns: Bright Infrared Extragalactic Spectroscopic (RUBIES) survey and other public JWST programs. We measure the density contrast in these fields by applying a Monte Carlo Voronoi tessellation density-mapping technique to photometric and spectroscopic redshifts of m _F444W < 27.5 sources. We robustly detect 19 massive overdense peaks with log ( M Peak / M ⊙ ) ≥ 13 and seven extended massive protoclusters ( log ( M Struct / M ⊙ ) ≥ 13.85 ). We observe that MQGs are preferentially found in these massive peaks and within these massive structures: ≈50% of MQGs are found in massive peaks, compared to ≈25% of massive star-forming galaxies (MSFGs), and quiescent fractions are higher in these regions than in the coeval field. We show that when all stellar mass is assumed to form in situ, the inferred masses of MQG progenitors are significantly higher than those of high- z massive galaxies in observations or simulations. Accounting for ex situ star formation and scaling merger rates by the local galaxy overdensity significantly lessens this tension, which indicates that ex situ star formation plays a key role in MQG mass assembly in overdense environments.

We present spectrally resolved structural parameter measurements of 28,274 sources from the legacy lensing field of A2744, quantifying global structures from the observed 0.7−4.8 μ m and spanning rest-frame UV to near-infrared (NIR) at R ∼ 15. These measurements are made on imaging mosaics mainly from the UNCOVER/MegaScience survey, including 20 JWST NIRCam broad and medium bands. We perform single-component Sérsic fitting to these galaxies using pysersic , a Bayesian structural fitting tool, to infer their structural parameters and associated random uncertainties from the posterior distributions. Through various quality evaluation criteria, we infer robust structural parameters among >85% of the selected signal-to-noise-ratio (SNR) > 10 sources. For each galaxy with reliable sizes in at least two bands and a high-quality redshift, we fit its observed size as a function of wavelength and infer rest-frame UV, optical, and NIR sizes where applicable. By performing injection-recovery tests on simulated galaxy cutouts in selected bands, we establish that our structural parameter measurements achieve a fractional error 10. With this paper, all raw structural measurements and fitted rest-frame sizes are quality flagged, cataloged, and released to the community. Finally, we demonstrate that this catalog enables the structural study of galaxies over an unprecedentedly wide parameter space of redshift (0.3 < z < 8), stellar mass (10 ⁷ M _⊙ < M _* < 10 ^11.5 M _⊙ ), and rest-frame optical size (100 pc < R _e < 10 kpc), after correcting for lensing magnification.

Dynamical tracers provide key measurements of galaxies’ total masses, complementing other methods of determining stellar and gas masses and also providing some of the only possible constraints on their dark matter content. Until recently, the deep spectrally-resolved observations necessary for these measurements were only accessible out to relatively low redshifts. Thanks to new observatories and instruments, particularly near infrared multi-object spectrographs as well as sub-mm interferometers, galaxy dynamical masses can now be measured out to the peak epoch of cosmic star formation and even earlier epochs. Here I give an overview of dynamical mass constraints of galaxy-scale dark matter fractions from the present day out to z ∼ 3. I also discuss comparisons between measurements from different dynamical tracers, and the modeling challenges and degeneracies that complicate our interpretations of observations.

We report the discovery of two z ∼ 12 galaxy candidates with unusually red UV slopes ( β _UV ≳ −1.5), and probe the origin of such colors at cosmic dawn. From Prospector fits to the UNCOVER/MegaScience dataset—deep JWST/NIRCam imaging of A2744 in 20 broad- and medium bands—we identify several new z > 10 galaxies. Medium-band data improve redshift estimates, revealing two lensed ( μ ∼ 3.3) z ∼ 12 galaxies in a close pair with β _UV ≳ −1.5 at an UV absolute magnitude of M _UV ∼ −19 mag, lying away from typical scatter on previously known M _UV – β _UV relations. Spectral energy distribution fitting with Prospector , Bagpipes , and EAZY support their high- z nature, with probability of low- z interlopers of p ( z < 7) < 10%. The potential low- z interlopers are z ∼ 3 quiescent galaxies (QGs), but unexpected to be detected at the given field of view unless z ∼ 3 QG stellar mass function has a strong turn up at log M * [ M ⊙ ] ∼ 9 . Unlike typical blue high-redshift candidates ( β _UV ≲ −2.0), these red slopes require either dust or nebular continuum reddening. The dust scenario implies A _V ∼ 0.8 mag, which is larger than theoretical predictions, but is consistent with a dust-to-stellar mass ratio ( log M dust / M * ∼ − 3 ). The nebular scenario demands dense gas ( log n H [ cm − 3 ] ∼ 4.0 ) around hot stars ( log T eff [ K ] ∼ 4.9 ). Spectroscopic follow-up is essential to determine their true nature and reveal missing galaxies at the cosmic dawn.

We present gas-phase radial metallicity profiles for 20 main-sequence galaxies at 4 < z < 6 primarily based on JWST NIRSpec IFU observations obtained as part of the JWST-ALPINE-CRISTAL programme. Our study aims to connect the metallicity gradients of these galaxies with their kinematic properties from [C II ] 158 μm ALMA observations. We mapped the radial profiles of oxygen abundance using the strong-line method, leveraging the rich set of rest-frame optical emission lines. Linear fits to the annular-binned radial profiles show that, on average, the metallicity gradients are slightly positive with a median of +0.039 ± 0.010 dex kpc ⁻¹ . However, only three galaxies show a gradient > 0.05 dex kpc ⁻¹ at 1 σ , and none have a significant negative gradient. There are no substantial systematic offsets in gradients when using different line diagnostics. We investigated the correlation between the metallicity gradients and the intrinsic gas velocity dispersion σ ₀ as well as the V _rot / σ ₀ ratio of the disks. Combining our sample with mass-matched literature samples at 3 ≲ z ≲ 7, we found a negative shallow correlation between V _rot / σ ₀ and the metallicity gradients, but no strong relationships with σ ₀ . As V _rot / σ ₀ increases towards later cosmic times, the observed negative trend with V _rot / σ ₀ is consistent with the overall cosmic evolution of metallicity gradients from high to low redshifts. This suggests that disk maturity plays a crucial role in shaping the radial metallicity gradients. We do not find the metallicity gradients of disk galaxies to be significantly different from non-disk galaxies, which could be attributed to the frequent accretion events that took place in these gas-rich systems. Additionally, we find no strong dependence of metallicity gradients on stellar mass and only a marginal positive dependence on specific star-formation rate. Our study extends the efforts to connect the internal kinematics of galaxies with their gas-phase chemical enrichment at kiloparsec scales from cosmic noon to z > 4.

Massive quiescent galaxies have been identified out to z ∼ 7 in early JWST data, substantially exceeding (≳1 dex at z > 4) the number densities from most theoretical predictions. We investigate whether the number densities implied by the star formation histories (SFHs) of quiescent galaxies at 2 < z < 5 are consistent with the observed number density evolution of that population since z > 7. For this work, we rely on stellar population synthesis modeling of JWST/NIRCam photometry (from CEERS and PRIMER) and NIRSpec/PRISM spectra of massive ( M _* > 10 ^10.5 M _⊙ ) quiescent galaxies in the RUBIES survey. We infer their SFHs through Bayesian spectrophotometric fitting with Prospector , exploring the sensitivity of our results to stellar libraries and SFH priors. For each source, we compute the timescale over which it would be identified as quiescent—leveraging the recent and most robust SFH timescale—and deduce the number densities of the quiescent population at previous epochs. These reconstructed number densities are then compared to existing observational constraints, including a new measurement from the PANORAMIC pure parallel survey, whose wide area and independent sight lines reduce sensitivity to cosmic variance. We find striking agreement between the reconstructed and observed number densities up to z ∼ 7, a self-consistency that lends credence to stellar population synthesis modeling of distant quiescent galaxies. Furthermore, by connecting the recent (∼1 Gyr) SFHs and number densities of quiescent galaxies and their implied progenitors, we reinforce the known tension between observations and model predictions at 3 < z < 7.

Spatially resolved stellar populations of massive quiescent galaxies at cosmic noon provide powerful insights into star-formation quenching and stellar mass assembly mechanisms. Previous photometric studies have revealed that the cores of these galaxies are redder than their outskirts. However, spectroscopy is needed to break the age-metallicity degeneracy and uncover the driver of these colour gradients. In this work, we derive the age and elemental abundance gradients for eight distant (1.2 ≲ z ≲ 2.2), massive (10.3 ≲ log( M _* /M _⊙ )≲11.1) quiescent galaxies by fitting full-spectrum models to ultra-deep NIRSpec-MSA spectroscopy from the JWST -SUSPENSE survey. We find that these galaxies have negative age and flat [Fe/H] gradients as well as tentative indications of positive [Mg/H] and [Mg/Fe] gradients. These results suggest that galaxy cores are older and perhaps also Mg deficient compared to galaxy outskirts. The age gradients may indicate inside-out quenching, while Mg-deficient cores could suggest rapid gas expulsion as the central quenching mechanism. Thus, galaxy cores may have formed faster and quenched more efficiently than their outskirts. In this scenario, however, our [Fe/H] and [Mg/Fe] gradients are still puzzling, and further investigation is required to understand the nature of [Mg/H] gradients in massive quiescent galaxies at these redshifts. Our results contrast with those of lower-redshift studies, which find flat age and [Mg/Fe] gradients and negative metallicity gradients. Additionally, we find a positive trend between age gradients and rotational support and marginal trends between [Fe/H] gradients and galaxy velocity dispersions and ages. We discuss our findings in the context of galaxy growth scenarios, including minor mergers and progenitor bias. With this work, we present the first stellar population gradients from NIRSpec-MSA spectroscopy in the current largest sample of distant quiescent galaxies.

Cosmic noon represents the prime epoch where today's massive galaxies assembled most of their stellar masses, and it is an ideal period for observations with both the space-based (JWST) and ground-based near-IR integral-field unit (IFU) spectrographs. This work analyzes JWST NIRSpec Micro Shutter Array (MSA) and NIRCam Wide Field Slitless Spectroscopy (WFSS) observations of $), and ionization parameter (log(U)≃-3.0). The central bulge is modestly massive (M_⋆=(7±3)times10^9 M_⊙), heavily obscured (A_V=6.43±0.55), and likely formed most of its stellar mass in the past (SFR=82±42 James Webb Telescope a large spiral, star-forming (SF) galaxy at z=2.224 with evidence of radial gas inflows. Leveraging ground-based IFU ERIS observations, we conducted a comprehensive and resolved study of the interstellar medium and stellar properties of this galaxy, covering the rest-frame optical to near-IR. Our analysis -- using several emission-line diagnostics, resolved spectral energy distribution (SED) fitting of high-resolution imaging, and line detection in NIRCam WFSS data -- reveals massive SF clumps (M_⋆≃(0.67-3.5)times10^9 M_⊙) with star formation rates (SFRs) of 3-24 low dust attenuation (A_V≃0.4), electron densities (n_̊m ełesssim300 cm -3 over the last ∼100 Myr). Yet, it continues to form stars at a lower rate (SFR$=12 over the last ∼10 Myr). We infer a relatively low sulfur abundance of log(S/O)≃-1.9, which may have implications for sulfur production via type I supernova explosions. Moreover, all distinct galaxy regions feature a metallicity of 12+log(O/H)≈8.54, likely due -- along with the enhanced N/O abundance (i.e., log(N/O)≃$-1.0) -- to dilution effects from radial inflows of metal-poor gas. Lastly, we find tentative evidence of a negative gradient in stellar age, suggesting possible inside-out growth for