arXiv subjects

Adam Muzzin

Publications and source records attributed to Adam Muzzin.

At least 37 records · Page 2Linked to original sources

arXiv2025

The Stellar Mass and Age Distributions of Star-Forming Clumps at $0.5 < z < 5$ in JWST CANUCS: Implications for Clump Formation and Destruction

We investigate the resolved properties of star-forming clumps and their host galaxies at $0.5<z<5$ in the JWST CANUCS fields. We find that the fraction of clumpy galaxies peaks near $z\sim2$ for galaxies with masses of $\log(M_{g,*}/M_\odot)\geq10$, while galaxies with masses of $8.5 \leq \log(M_{g,*}/M_\odot) < 10$ show lower clumpy fractions with little redshift evolution. We identify and measure individual clump masses, finding that the aggregated clump stellar mass function (cSMF) follows a power-law slope of $\alpha = -2$ across all redshift bins, broadly consistent with \textit{in-situ} clump formation. However, when split by galaxy masses, the cSMF is found to be flatter ($\alpha\sim-1.6$) for massive galaxies and steeper ($\alpha\sim-2.3$) for lower mass galaxies, with little redshift evolution in both cases. We explore how different formation mechanisms and disruptive processes affect the shape of the clump mass function. In particular, we find that the cSMF slope is flatter with increasing gas fractions in younger clump populations ($<300$ Myr old), suggesting that higher gas availability leads to more massive clumps forming at the time of formation. Alternatively, many high-redshift galaxies in the sample have disturbed morphologies and simulations show that clumps of \textit{ex-situ} origins can flatten the cSMF slope. We also investigate the evolution of clump populations, where we find the cSMF slope become flatter as clumps evolve and age. We interpret this as an indication of the long-term survivability of massive clumps, with feedback mechanisms preferentially disrupting low-mass clumps. Overall, the galaxy-mass dependent cSMF and age distribution point to a complex history for clumps, involving different and competing mechanisms for their formation and destruction.

astro-ph.GA↗

arXiv2025

Probing the Star Formation Main Sequence down to 10$^{7} M_\odot$ at $1 < z < 9$

The Main Sequence of Star-Forming Galaxies (SFGMS or MS) is a fundamental scaling relation that provides a global framework for studying galaxy formation and evolution, as well as insight into the complex star formation histories (SFHs) of individual galaxies. In this work, we combine large-area pre-JWST surveys (COSMOS2020, CANDELS), which probe high-$M_\star$ sources (${>10^9\,M_\odot}$), with SHARDS/CANDELS FAINT and JWST data from CANUCS, CEERS, JADES, and UNCOVER, to obtain a high-$z$, star formation rate (SFR) and stellar mass ($M_\star$) complete sample spanning both high- and low-$M_\star$ regimes. Completeness in both $M_\star$ and SFR is key to avoiding biases introduced by low-mass, highly star-forming objects. Our combined data set is 80% complete down to $10^{7.6}\,M_\odot$ at $z\sim1$ ($10^{8.8}\,M_\odot$ at $z\sim9$). The overall intrinsic MS slope (based on the SFR$_{100}$ and $M_\star$ derived with Dense Basis and nonparametric SFHs) shows little evolution up to $z\sim5$, with values $\sim0.7 - 0.8$. The slope in the low-$M_\star$ regime becomes steeper than that in the high-$M_\star$ end at least up to $z\sim5$, but the strength of this change is highly dependent on the assumptions made on the symmetry of the uncertainties in $M_\star$ and SFR. If real, the steepening suggests reduced star formation efficiency or declining gas content with decreasing $M_\star$. The transition between the low-$M_\star$ regime and the canonical MS occurs around $10^{9.5}\,M_\odot$, independent of $z$. This critical value may coincide with the assembly of galaxies' disks, which can provide a mechanism for self-regulation that stabilizes them against feedback. The intrinsic scatter is compatible with canonical estimates, also at low-$M_\star$, ranging from $0.2-0.3$ dex. This is indicative of rapid variations in star formation being averaged out over $\lesssim100$ Myr.

astro-ph.GA↗

arXiv2025

JWST Photometry of Globular Cluster Populations in MACS0417.5-1154

Deep JWST imaging of the massive galaxy cluster MACS0417.5-1154, at redshift z=0.443, reveals a huge population of globular clusters (GCs) and Ultra-Compact Dwarfs (UCDs) primarily distributed around its single central giant galaxy (BCG). We present NIRCam/SWC photometry of the GC system in four bands (F090W, F115W, F150W, F200W). The spatial distribution of the system matches well in radial and ellipticity profile with the high elongation (b/a = 0.5) of the BCG halo light. The total GC population within MACS0417 is estimated to be near 1.5 x 10^5, similar to the systems in Abell 2744, Coma, and other galaxy clusters with comparable masses. With similar results for GC photometry in hand from other lensing clusters at a range of redshifts, it is now possible to trace on purely observational grounds the luminosity evolution of GC systems over many Gigayears of lookback time, as seen through their color-magnitude diagrams. We show this sequence for five systems reaching to lookback times of more than 7 Gyr. A systematic change in the GC/UCD sequence with lookback time is clearly visible, near what is expected for age-fading of a simple stellar population with time. Lastly, we evaluate the effectiveness of the various JWST NIRCam filters for broadband photometry of GC systems as a function of redshift, as an aid to planning further studies.

astro-ph.GA↗

arXiv2025

Clues to inside-out quenching in quiescent galaxies at $1.2\lesssim z\lesssim2.2$: Age, Fe-, and Mg-abundance gradients from JWST-SUSPENSE

[Abridged] Spatially resolved stellar populations of massive quiescent galaxies at cosmic noon provide powerful insights into quenching and 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 colour gradients. We derive age and elemental abundance gradients for eight distant ($1.2 \lesssim z \lesssim 2.2$), massive ($10.3\lesssim\log({\rm M}_*/{\rm M}_\odot)\lesssim 11.1$) 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, and 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. 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 galaxies at these redshifts. Our results contrast with those of lower-$z$ 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 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.

astro-ph.GA↗

arXiv2025

A massive and evolved slow-rotating galaxy in the early Universe

In the contemporary Universe, most galaxies are supported by ordered rotation, yet a significant subset of the most massive and quiescent systems are dominated by random stellar motions and classified as slow rotators. These galaxies are widely thought to arise through processes that remove angular momentum and erase disk-like structures, but when and how this transformation occurs remains uncertain. Slow rotators are expected to be rare at early cosmic times, and observational studies of massive galaxies at high redshift have so far revealed only rapidly rotating systems. Here we report James Webb Space Telescope near-infrared integral field spectroscopy of XMM-VID1-2075, a massive quiescent galaxy at $z=3.449$. The galaxy displays disturbed low-surface-brightness features and a low stellar spin parameter, $\lambda_{R_e} = 0.123^{+0.073}_{-0.023}$, consistent with dispersion-dominated kinematics. These results demonstrate that the formation of slow-rotating massive galaxies was already underway when the Universe was less than 2 Gyr old.

astro-ph.GA↗

arXiv2025

MAGAZ3NE: Far-IR and Radio Insights into the Nature and Properties of Ultramassive Galaxies at $z\gtrsim3$

Deep and wide-field near-infrared (NIR) surveys have recently discovered and confirmed ultramassive galaxies (UMGs; $\log (M_{\star}/M_{\odot})>11$) spectroscopically at high redshift. However, most are characterized using only ultraviolet (UV)-to-NIR photometry, offering limited insight into obscured star formation and active galactic nucleus (AGN) activity. In this work, we add ten far-infrared (FIR)-to-radio passbands to the existing UV-to-NIR catalogs for two spectroscopically confirmed UMGs from the MAGAZ3NE survey, COS-DR3-195616 ($z_{\rm spec} = 3.255$) and COS-DR1-209435 ($z_{\rm spec} = 2.481$). Utilizing the full UV-to-radio photometry, we revise our earlier UV-NIR-based interpretation of the nature of these galaxies. While both were previously identified as quiescent, our analysis reveals that 195616 is an unobscured galaxy undergoing quenching, and 209435 is a heavily obscured, actively star-forming UMG. We find that 195616 has already depleted most of its molecular gas and is expected to experience minimal future stellar mass growth. In contrast, 209435 contains a substantial molecular gas reservoir and has a prolonged depletion timescale. It is anticipated to increase 0.34 dex in stellar mass, reaching a stellar mass of $\log (M_{\star}/M_{\odot})$ = 11.72 over the next 0.72 Gyr. We present multi-pronged evidence for AGN activity in both UMGs. Our findings support a scenario where AGN feedback in 195616 may have contributed to gas depletion during quenching, while 209435 continues to form stars despite hosting an obscured AGN, suggesting feedback has not yet suppressed star formation. Our work shows the importance of FIR-to-radio observations for accurately inferring the nature and properties of galaxies at $z\gtrsim3$.

astro-ph.GA↗

arXiv2025

Excavating The Ruins: an Ancient $z=2.675$ Galaxy Which Formed in the First 500 Myr

We present the analysis of an ancient galaxy at $z=2.675$ which we dub ``Eridu.'' Simultaneously modeling the JWST/NIRSpec G140M and G235M spectra from the SMILES program and $0.4-25\ \mu\mathrm{m}$ HST, JWST/NIRCam, and JWST/MIRI photometry from the the JADES+SMILES photometric catalogs shows that Eridu is massive and quiescent with stellar mass $\log(M_*/\mathrm{M_\odot})=10.96^{+0.01}_{-0.01}$ and average star formation rate $<1\ \mathrm{M_\odot\ yr^{-1}}$ over the last 100 Myr. Star formation histories inferred from various models produce disconcertingly early and fast formation within $\sim300$ Myr of the Big Bang and quenching 2 Gyr prior to observation ($z\sim10$). This stellar mass assembly implies that the progenitor of Eridu had $M_*\approx10^{11}\ \mathrm{M_\odot}$ at $z>10$, nearly two orders of magnitude more than the most massive current high redshift observations. From Eridu's spectrum we infer $\mathrm{[Mg/Fe]} =+0.65^{+0.20}_{-0.19}$, indicating its stellar population is extremely $\alpha$-enhanced, which is consistent with the rapid formation timescale inferred from its star formation history. Eridu inhabits a massive protostructure which offers additional explanations for rapid mass assembly and quenching via environmental mechanisms, e.g. major mergers. Though its inferred formation is at odds with observations of the brightest cosmic dawn galaxies, we anticipate that future high-redshift galaxy formation models and sophisticated stellar population modeling codes will unearth how Eridu formed at the dawn of time.

astro-ph.GA↗

arXiv2025

Metal-Poor Star-Forming Clumps in Cosmic Noon Galaxies: Evidence for Gas Inflow and Chemical Dilution Using JWST NIRISS

The formation and evolution of galaxies are intricately linked to the baryon cycle, which fuels star formation while shaping chemical abundances within galaxies. Investigating the relationship between star formation and metallicity for large samples of galaxies requires expensive IFU surveys or sophisticated tools to analyze grism data. Here we analyze JWST NIRISS slitless grism data using Sleuth, a tool that forward models and infers spatially resolved physical properties from grism data, including observations from JWST NIRISS/NIRCam and future grism data like that from the Roman Space Telescope. Sleuth enables extraction of high-quality emission line maps from slitless spectra, overcoming contamination and spatially varying stellar populations, which previously limited such studies. Utilizing Sleuth with data from the CAnadian NIRISS Unbiased Cluster Survey (CANUCS), we investigated the relationship between metallicity and star formation in the star-forming clumps of galaxies at 0.6 < z < 1.35. We analyzed a sample of 20 galaxies, extracted high-quality emission line maps with Sleuth, and analyzed, in detail, the spatially resolved properties of star-forming clumps. Using $H\alpha$, [SII], and [SIII] emission line maps, we examined the spatially resolved metallicities, ionization, and star formation rates of our sample. Our findings reveal that these star-forming clumps show lower metallicities ($\sim$ 0.1 dex) than their surrounding galactic environments, indicating a metallicity dilution of 20 $\%$ within the clumps' gas. Our analysis indicates that these clumps exhibit intensified star formation and reduced metallicity, likely due to the inflow of metal-poor gas. These clumps illustrate the dynamic relationship between star formation and chemical enrichment within galaxies.

astro-ph.GA↗

arXiv2025

MINERVA: A NIRCam Medium Band and MIRI Imaging Survey to Unlock the Hidden Gems of the Distant Universe

We present an overview of the MINERVA survey, a 259.8 hour (prime) and 127 hour (parallel) Cycle 4 treasury program on the James Webb Space Telescope (JWST). MINERVA is obtaining 8 filter NIRCam medium band imaging (F140M, F162M, F182M, F210M, F250M, F300M, F360M, F460M) and 2 filter MIRI imaging (F1280W, F1500W) in four of the five CANDELS Extragalactic fields: UDS, COSMOS, AEGIS and GOODS-N. These fields were previously observed in Cycle 1 with 7 - 9 NIRCam filters by the PRIMER, CEERS and JADES programs. MINERVA reaches a 5$\sigma$ depth of 28.1 mag in F300M and covers $\sim$ 542 arcmin$^2$, increasing the area of existing JWST medium-band coverage in at least 8 bands by $\sim$ 7$\times$. The MIRI imaging reaches a 5$\sigma$ depth of 23.9 mag in F1280W and covers $\sim$ 275 arcmin$^2$ in at least 2 MIRI filters. When combined with existing imaging, these data will provide a photometric catalog with 20-26 JWST filters (depending on field) and 26-35 filters total, including HST. This paper presents a detailed breakdown of the filter coverage, exposure times, and field layout relative to previous observations, as well as an overview of the primary science goals of the project. These include uncovering the physics of enigmatic sources hiding in current broadband catalogs, improving systematics on stellar mass functions and number densities by factors of $\gtrsim$ 3, and resolved mapping of stellar mass and star formation at 1 $< z <$ 6. When complete, MINERVA will become an integral part of the treasury deep field imaging datasets, significantly improving population studies with well-understood completeness, robust photometric redshifts, stellar masses, and sizes, and facilitating spectroscopic follow up for decades to come.

astro-ph.GA↗

arXiv2025

Earliest Galaxy Evolution in the CANUCS+Technicolor fields: Galaxy Properties at $z\sim10-16$ seen with the Full NIRCam Medium and Broad Band Filters

We present a sample of $z_{\rm phot}\sim10-16$ galaxies by exploiting one of the richest JWST NIRCam imaging data, taken in the CANUCS survey in Cycle 1 and the Technicolor (TEC) survey in Cycle 2. The combination of the CANUCS+TEC provides multi-epoch, deep NIRCam images in all medium bands (MBs) and broad bands (BBs) onboard NIRCam (22 filters in total), over $\sim23\ {\rm arcmin}^2$ in three independent lines of sight. We select high-$z$ galaxy candidates based on photometric redshifts, and obtain eight candidates at $z\sim10-16$, including a very robust candidate at $z\sim15.4$. The ultraviolet (UV) luminosity function (LF) from our sample is consistent with previous JWST studies showing a scatter of $\sim0.6$ dex across the literature, marking the significance of the field-to-field variance in interpreting galaxy abundance measurements at $z>10$. We find that the UV LF moderately evolves at $z>10$, and the LF normalization and the luminosity density decline by a factor of $\sim7$ from $z\sim11$ to $z\sim15$, indicating less steep evolution than $z<11$. We highlight the importance of MB filters, not only to minimize the contamination by low-$z$ interlopers but also to maximize the completeness. In particular, faint and less blue galaxies could be missed when the sample is built solely on BB data. The contamination and incompleteness of BB-only selected samples can bias our views of earliest galaxy evolution at $z>10$, including the UV LF by $\sim0.6$ dex, the size-magnitude relation by $\sim0.6$ dex, and the UV slope-magnitude relation by $\Delta\beta_{\rm UV}\sim-0.3$.

astro-ph.GA↗

arXiv2025

CANUCS/Technicolor Data Release 1: Imaging, Photometry, Slit Spectroscopy, and Stellar Population Parameters

We present the first data release of the CAnadian NIRISS Unbiased Cluster Survey (CANUCS), a JWST Cycle 1 GTO program targeting 5 lensing clusters and flanking fields in parallel (Abell 370, MACS0416, MACS0417, MACS1149, MACS1423; survey area \tilda100 arcmin$^{2}$), with NIRCam imaging, NIRISS slitless spectroscopy, and NIRSpec prism multi-object spectroscopy. Fields centered on cluster cores include imaging in 8 bands from 0.9-4.4$\mu$m, alongside continuous NIRISS coverage from 1.15-2$\mu$m, while the NIRCam flanking fields provide 5 wide and 9 medium band filters for exceptional spectral sampling, all to \tilda29 mag$_{AB}$. We also present JWST in Technicolor, a Cycle 2 follow-up GO program targeting 3 CANUCS clusters (Abell 370, MACS0416, MACS1149). The Technicolor program adds NIRISS slitless spectroscopy in F090W to the cluster fields while adding 8 wide, medium, and narrow band filters to the flanking fields. This provides NIRCam imaging in all wide and medium band filters over \tilda30 arcmin$^{2}$. This paper describes our data reduction and photometry methodology. We release NIRCam, NIRISS, and HST imaging, PSFs, PSF-matched imaging, photometric catalogs, and photometric and spectroscopic redshifts. We provide lens models and stellar population parameters in up to 19 filters for \tilda53,000 galaxies in the cluster fields, and \tilda44,000 galaxies in up to 29 filters in the flanking fields. We further present 733 NIRSpec spectra and redshift measurements up to $z=10.8$. Comparing against our photometric redshifts, we find catastrophic outlier rates of only 4-7\% and scatter of $\sigma_{\rm NMAD}$ of 0.01-0.03.

astro-ph.GA↗

arXiv2025

JWST Reveals a Candidate Jellyfish Galaxy at z=1.156

We report the discovery of COSMOS2020-635829 as a candidate jellyfish galaxy undergoing ram pressure stripping in a (proto)cluster at $z > 1$. High-resolution imaging from the James Webb Space Telescope reveals a symmetric stellar disk coupled to a unilateral tail of star-forming knots to the south. Using Gemini GMOS IFU observations, we show that these extra-planar continuum sources are embedded within an ionized gas tail that is kinematically connected to the disk of COSMOS2020-635829. If confirmed, this represents the highest-redshift discovery of a ram pressure stripped ionized gas tail. The tail sources are characterized by extremely young stellar populations ($\lesssim 100\,\mathrm{Myr}$), have stellar masses of ${\sim}10^8\,\mathrm{M_\odot}$, and star formation rates of $0.1\text{--}1\,\mathrm{M_\odot\,yr^{-1}}$. This work shows that ram pressure stripping can potentially perturb group and cluster galaxies at $z > 1$ and may contribute to environmental quenching even near Cosmic Noon.

astro-ph.GA↗

arXiv2025

Distinct origins of environmentally quenched galaxies in the core and outer virialised regions of massive clusters at $0.8<z<1.5$

High-redshift ($z\sim1$) galaxy clusters are the domain where environmental quenching mechanisms are expected to emerge as important factors in the evolution of the quiescent galaxy population. Uncovering these initially subtle effects requires exploring multiple dependencies of quenching across the cluster environment, and through time. We analyse the stellar-mass functions (SMFs) of 17 galaxy clusters within the GOGREEN and GCLASS surveys between $0.8 9.5$. The data are fit simultaneously with a Bayesian model that allows the Schechter function parameters of the quiescent and star-forming populations to vary smoothly with cluster-centric radius and redshift. The model also fits the radial galaxy number density profile of each population, allowing the global quenched fraction to be parameterised as a function of redshift and cluster velocity dispersion. We find the star-forming SMF to not depend on radius or redshift. For the quiescent population however, there is $\sim2\sigma$ evidence for a radial dependence. Outside the cluster core ($R>0.3\,R_{\rm200}$), the quenched fraction above $\log{(M/{\rm{M_\odot}})}=9.5$ is $\sim40{\rm\;per\,cent}$, and the quiescent SMF is similar in shape to the star-forming field. In contrast, the cluster core has an elevated quenched fraction ($\sim70{\rm\;per\,cent}$), and a quiescent SMF similar in shape to the quiescent field population. We explore contributions of 'early mass-quenching' and mass-independent 'environmental-quenching' models in each of these radial regimes. The core is well-described primarily by early mass-quenching, which we interpret as accelerated quenching of massive galaxies in protoclusters, possibly through merger-driven feedback mechanisms. The non-core is better described through mass-independent, environmental-quenching of the infalling field population.

astro-ph.GA↗

arXiv2025

Fast Rotators at Cosmic Noon: Stellar Kinematics for 15 Quiescent Galaxies from JWST-SUSPENSE

We present spatially-resolved stellar kinematics of 15 massive ($M_*=10^{10.5-11.5}M_{\odot}$) quiescent galaxies at $z\sim1.2-2.3$ from the JWST-SUSPENSE program. This is the largest sample of spatially-resolved kinematic measurements of quiescent galaxies at cosmic noon to date. Our measurements are derived from ultra-deep NIRSpec/MSA stellar absorption line spectra, using a forward modelling approach that accounts for optics, source morphology, positioning, and data reduction effects. 10 out of 15 galaxies are orientated such that we can measure rotational support. Remarkably, all 10 galaxies show significant rotation ($V_{r_e}=117-345$km/s, $\sigma_0 = 180-387$km/s), and are classified as "fast rotators" from their spin parameter. The remaining galaxies are too misaligned with respect to the slit to constrain their rotational velocities. The widespread rotational support in our sample indicates that the process responsible for quenching star formation in early massive galaxies did not destroy rotating disc structures. When combined with other quiescent galaxy samples at $z\sim0.5-2.5$, we find a trend between rotational support and age, with younger quiescent galaxies being more rotationally supported. This age trend has also been found at $z\sim0$, and likely explains why our high-redshift galaxies show more rotational support compared to massive ETGs at $z\sim0$, which are, on average, older. Our kinematic modelling also enables us to calculate dynamical masses. These dynamical masses greatly exceed the stellar masses for our sample (median $M_{\text{dyn}}/M_*=2.7$); they even allow for the bottom-heavy IMF found in the cores of low-$z$ massive ellipticals. Altogether, our results support a scenario in which distant quiescent galaxies evolve into nearby massive ETGs, gradually building up their outskirts and simultaneously losing rotation, due to a series of (mostly minor) mergers.

astro-ph.GA↗

arXiv2025

Traversing the Star-Forming Main Sequence with Molecular Gas Stacks of z~1.6 Cluster Galaxies

The cluster environment has been shown to affect the molecular gas content of cluster members, yet a complete understanding of this often subtle effect has been hindered due to a lack of detections over the full parameter space of galaxy star formation rates and stellar masses. Here we stack CO(2-1) spectra of z~1.6 cluster galaxies to explore the average molecular gas fractions of galaxies both at lower mass (log(M/solar mass)~9.6) and further below the Star Forming Main Sequence (SFMS; DeltaMS~ -0.9) than other literature studies; this translates to a 3sigma gas mass limit of ~7x10^9 solar masses for stacked galaxies below the SFMS. We divide our sample of 54 z~1.6 cluster galaxies, derived from the Spitzer Adaptation of the Red-Sequence Cluster Survey, into 9 groupings, for which we recover detections in 8. The average gas content of the full cluster galaxy population is similar to coeval field galaxies matched in stellar mass and star formation rate. However, when further split by CO-undetected and CO-detected, we find that galaxies below the SFMS have statistically different gas fractions from the field scaling relations, spanning deficiencies to enhancements from 2sigma below to 3sigma above the expected field gas fractions, respectively. These differences between z=1.6 cluster and field galaxies below the SFMS are likely due to environmental processes, though further investigation of spatially-resolved properties and more robust field scaling relation calibration in this parameter space are required.

astro-ph.GA↗

arXiv2025

UNCOVER/MegaScience: No Evidence of Environmental Quenching in a z$\sim$2.6 Proto-cluster

Environmental quenching -- where interactions with other galaxies and/or the intra-cluster medium (ICM) suppress star formation in low-mass galaxies -- has been well-established as the primary driver behind the formation of the red sequence for low-mass galaxies within clusters at low redshift ($z<1$). However, it remains unclear whether these mechanisms are active at higher-redshifts in proto-cluster environments that are not yet fully virialized. In large part, this regime has remained unexplored due to observational limitations; however, JWST has recently opened a new window into the role of environmental quenching on low-mass (log(M$_{\star}$/M$_{\odot}$$<$9.0) galaxies at cosmic noon ($2 < z < 3$). Here, we leverage the deep imaging and R$\sim$15 spectrophotometry enabled by the 20 band JWST/NIRCam data from the UNCOVER and MegaScience programs to examine environmental quenching in a newly discovered $z\approx2.58$ proto-cluster. We compare the star formation histories (SFHs) of 19 low-mass quiescent galaxies in the proto-cluster to a matched sample of 18 in the field, and find no significant differences. This similarity extends to galaxy sizes and quenched fractions, which also show no significant differences between the two environments across the full stellar mass range (8.5$<$log(M$_{\star}$/M$_{\odot}$$\leq$11.0). This indicates that the proto-cluster has not yet accelerated quenching relative to the field and is consistent with expectations that $z>2$ proto-clusters have yet to virialize and develop a dense enough environment required to efficiently quench low-mass galaxies.

astro-ph.GA↗

arXiv2025

CANUCS/Technicolor: JWST Medium Band Photometry Finds Half of the Star Formation at $z>7.5$ is Obscured

We present a sample of 146 high-redshift ($z>7.5$) galaxies from the CANUCS/Technicolor surveys, showcasing photometry in every wide- and medium-band NIRCam filter in addition to ancillary HST data sampling $0.4-5 \mu m$ (22 JWST bands out of 29 bands total). Additionally, 48 ($33\%$) galaxies in our sample meet criteria to be classified as extreme emission line galaxies, 15 ($10\%$) of which are completely missed by typical dropout selections due to faint UV emission. By fitting the SEDs covering the rest-frame UV to optical at $z > 7.5$, we investigate the dust obscuration properties, giving an unbiased view of dust buildup in high-redshift galaxies free from spectroscopic follow-up selection effects. Dust attenuation correlates with stellar mass, but more strongly with star formation rate. We find typical galaxies at $z>7.5$ have $\sim 25 \%$ of their star formation obscured. However, since galaxies with higher star formation rates suffer more attenuation, $\sim 50 \%$ of the total star formation rate density at $7.5 15$, implying that epoch as when dust first forms in bright galaxies.

astro-ph.GA↗

arXiv2025

In Search of the First Stars: An Ultra-Compact and Very Low Metallicity Lyman-$\alpha$ Emitter Deep Within the Epoch of Reionization

We present {\it JWST} observations of a gravitationally-lensed, extremely metal-poor galaxy at redshift $z=8.203\pm 0.001$ from the CANUCS survey. Based on the low oxygen to Balmer line ratios we infer a gas-phase metallicity of $12+{\rm log(O/H)}=6.85$ (1.4\% solar), making CANUCS-A370-z8-LAE one of the most metal-poor galaxies known at $z>7$. With a high H$\beta$ equivalent width of $225\pm50$\,\AA\ and a half-light radius of only $r_{\rm hl} = 38 ^{+3}_{-19} $\,pc, the galaxy has a high star-formation-rate density of $50 - 100\,M_{\odot}$\,yr$^{-1}$\,kpc$^{-2}$. The galaxy shows high equivalent width Lyman-$\alpha$ emission with an inferred Lyman-$\alpha$ escape fraction of $0.21 \pm 0.05$. The high escape fraction of Lyman-$\alpha$ is likely due to the compact starbursting nature of the galaxy combined with its location in an overdensity traced by at least two other galaxies spectroscopically confirmed to lie within $\delta z = 0.01$ that have helped to reionize the environment. The low metallicity of CANUCS-A370-z8-LAE is best explained by a model where infalling metal-poor gas dilutes the interstellar medium, rather than being a young galaxy forming its first stellar populations.

astro-ph.GA↗