arXiv subjects

Ryan Endsley

Publications and source records attributed to Ryan Endsley.

At least 19 recordsLinked to original sources

arXiv2026

The MIRI Early Obscured-AGN Wide Survey (MEOW): A Population of Hidden AGN at $z \gtrsim 5$ Revealed by JWST/MIRI Imaging

We present the MIRI Early Obscured-AGN Wide Survey (MEOW), a JWST/MIRI imaging survey designed to detect dust-obscured active galactic nuclei (AGN) across cosmic time, with a particular focus on the high-redshift universe at $z \gtrsim 5$. MEOW observes the GOODS-N and GOODS-S fields with 43 pointings covering 95 arcmin$^2$ with the F1000W and F2100W filters, reaching depths of 0.5 and 3.6 $\mu$Jy ($5\sigma$), respectively. Using spectral energy distribution (SED) modeling combining MEOW photometry with archival HST, JWST/NIRCam, and SCUBA-2 data, we identify a sample of 16 MIRI-selected AGN at $z = 4.5$--$7.2$ (12 spectroscopically confirmed), spanning bolometric luminosities of $L_{\rm bol} = 10^{44.6}$--$10^{46.4}$~erg~s$^{-1}$. Twelve of the 16 AGN are newly identified in this work, including at least five narrow-line AGN representing the obscured population to which broad-line spectroscopic searches are insensitive. Two broad-line AGN exhibit markedly different mid-infrared emission properties, consistent with one being a little red dot (LRD) and the other either a typical AGN or an LRD with unusually strong hot-dust emission. The MIRI-selected AGN bolometric luminosity function at $z = 4.5$--$6$ yields number densities comparable to those of broad-line AGN and LRDs, suggesting that obscured AGN contribute significantly to the total AGN census at these epochs. The narrow-line AGN reside in diverse host environments, with evidence for both circumnuclear and host-galaxy-scale obscuration, pointing to multiple physical mechanisms at work. These results establish JWST/MIRI imaging as an indispensable component of a multi-faceted approach to a complete census of early supermassive black hole growth.

astro-ph.GA↗

arXiv2026

JWST absorption line spectroscopy with SPURS: ISM covering fractions and kinematics in individual galaxies at $z=5-9$

We present deep rest-ultraviolet (UV) spectra of six luminous $z=5$ -- 9 galaxies in the Abell-2744 field taken as part of the JWST Cycle 4 Large Program SPURS. The individual galaxy spectra show unambiguous detections of interstellar medium (ISM) metal absorption lines from low- and high-ionization states of enriched gas, which we use to probe the ISM gas porosity and kinematics. We find a striking diversity in the absorption profiles. We find low-ionization gas covering fractions ranging from 0.2 to 0.9, indicating a heterogeneous and patchy neutral ISM. The low-ionization kinematics also show a large diversity, with velocity centroid values ranging from $+$70 to a significantly blueshifted $-140$ km$\,$s$^{-1}$, while the high-ion gas shows mostly blueshifted absorption, indicating the presence of multiphase outflows. While all sources show outflow signatures in blueshifted wings, we also find that half of our sample, in particular those with the lowest stellar masses and highest sSFRs, have low-ionization velocity centroids close to systemic velocities. This is in contrast to near-ubiquitous bulk low-ionization gas outflows at lower redshifts. We suggest that this diversity of kinematics may be due to the bulk of the cold gas having low outflow velocities in the lowest mass and highest sSFR systems, potentially due to inefficient entrainment and/or an unresolved infalling component. These spectra reveal a metal-enriched ISM with complex gas geometry and kinematics, and highlight the potential of deep JWST grating spectroscopy to reveal the properties of the ISM during the reionization era.

astro-ph.GA↗

arXiv2026

A GLIMPSE of the 99%: a census of the faintest galaxies during the epoch of reionization and its implications for galaxy formation models

We present a comprehensive study of the galaxy UV luminosity function (UVLF) at $z=6-9$ leveraging deep JWST observations from the GLIMPSE survey. Thanks to gravitational lensing, we probe the UVLF to an unprecedented depth of $M_{\text{UV}} = -12$ mag, approximately three magnitudes deeper than previous robust constraints. Our UVLF determination incorporates a rigorous end-to-end uncertainty framework, including statistical and systematic lensing uncertainties. We find that the $z \sim 7$ UVLF continues to rise steeply with a faint-end slope of $\alpha = -1.98_{-0.05}^{+0.06}$. Crucially, our data show no clear evidence of a turnover down to \muv $= -12.3$. The persistence of this faint population provides stringent constraints on galaxy formation models and cosmological simulations that predict an early flattening of the luminosity function due to radiative feedback or star-formation thresholds. Furthermore, post-JWST models specifically calibrated to match the UV-bright excess at $z > 10$ generally fail to reproduce the observed evolution toward lower redshifts and fainter magnitudes, highlighting a significant tension in our current understanding of early galaxy assembly. We derive a comoving ionizing emissivity at $z=7$ of log($n_{\mathrm ion}$ / s$^{-1}$ Mpc$^{-3}$) $\approx 50.85$, which suggests that faint galaxies dominate the ionizing budget, providing enough photons to maintain reionization even in a highly clumped IGM ($C_{\text{HII}} = 5$). As our detection of faint galaxies effectively rules out a luminosity function truncation at $M_{\text{UV}} \geq -15$, these results emphasize the need to either accurately characterize the ionizing properties of the global, low-mass galaxy population at $z > 6$, or to refine physical models of intergalactic medium clumping and its redshift evolution to maintain consistency with the observed reionization timeline.

astro-ph.GA↗

arXiv2026

SPURS: Bursty Star Formation in an Extremely Luminous Weak Emission Line Galaxy at $z=9.3$

JWST has revealed a population of super-luminous early galaxies with a volume density in excess of most expectations. The spectra reveal diverse properties: while some reveal strong emission lines characteristic of galaxies in the midst of strong bursts, others show weak emission lines that could reflect old stellar populations, large escape fractions, or post-burst star formation histories. Through the JWST Cycle 4 large program SPURS, we have obtained ultra-deep (29 hr) rest-frame UV spectroscopy of a z=9.3 super-luminous ($M_{\rm UV}=-21.66$) galaxy with large assembled stellar mass (1.6$\times$10$^9$ $M_\odot$) and extremely weak emission lines (H$\beta$ EW $\approx25$~\AA). The strong stellar wind features and rest-optical line ratios suggest the galaxy is already significantly enriched, with a metallicity of 0.4--0.7~Z$_\odot$. The interstellar absorption lines reveal outflows ($v\simeq -161$~km~s$^{-1}$) with a large neutral gas covering fraction, suggesting that the weak emission lines are not due to large escape fractions. The combination of the Balmer break, weak emission lines, and stellar wind features constrains the star formation history, indicating a recent burst of star formation lasting 10--20 Myr followed by a downturn over the last 10~Myr. The observations suggest that $z\gtrsim 9$ weak emission line galaxies such as this source can be explained by stochastic star formation, provided that the downturns in star formation are recent (i.e., <10 Myr prior to observation). The ultra-deep grating spectrum enables the IGM damping wing to be characterized, decoupling the effects of local absorption. The smooth Ly$\alpha$ break indicates that this source, one of the most massive galaxies known at z>9, is likely situated in a small ionized bubble ($0.29_{-0.09}^{+0.11}$~pMpc), as is common at large neutral hydrogen fractions ($\bar{x}_{\rm HI}=0.81_{-0.21}^{+0.14}$).

astro-ph.GA↗

arXiv2026

Other red dots: A possible GLIMPSE of normal AGB stars at Cosmic Noon through extreme lensing

We report the discovery of four extremely faint ($m_{\mathrm{F444W}}\gtrsim29$) red point sources in recent ultra-deep JWST/NIRCam images of the strong lensing galaxy cluster Abell S1063. All four sources sit in lensed arcs, on the symmetry points very close to the critical curves for their host-galaxies' redshifts ($z\sim1-4$). Remarkably, these point sources appear in most arcs that are sufficiently faint close to the critical curve's position ($<21\,\mathrm{nJy}\,\mathrm{arcsec}^{-2}$ in F115W). This suggests that -- unlike previous caustic-crossing events or lensed stars -- thanks to the unprecedented depth of the GLIMPSE observations paired with the extreme lensing magnification (up to $\mu\sim10^4$) we might be resolving the lower-mass ($M\sim1-11\,\mathrm{M}_{\odot}$) red stellar population. Concretely, we detect three likely extremely magnified asymptotic giant branch (AGB) stars ($T_{\mathrm{eff}}\sim3200-3750$ K), and one yellow super-giant star ($T_{\mathrm{eff}}\sim6750$ K) -- possibly a yellow hyper-giant or a Cepheid. In addition to offering the first glimpse at low-mass extremely magnified stars, these detections open a possible window into stellar populations, evolution, and chemical enrichment at high redshifts, and could pave the way for using lensed stars such as these as standard candles to populate the distance ladder at cosmological redshifts.

astro-ph.GA↗

arXiv2026

GLIMPSED: Direct evidence for a fast AGN-driven outflow from a z=6.64 Little Red Dot host galaxy

We report the discovery of GLIMPSED-329380, a z=6.64 galaxy behind Abell S1063, which shows signs of an extreme ionised outflow driven by an active galactic nucleus (AGN). The deep JWST/NIRSpec medium grating observations show spatially resolved structures of a host galaxy containing the very fast outflow and an AGN, which we analyse separately. The outflow, mainly traced by broad [O III]{\lambda}5008 and H{\alpha} emissions in the host, reaches a full-width half-maximum velocity of ~5500km/s, velocities only observed in AGN-dominated systems. From the Balmer decrement, we observe that while the narrow emission lines show no dust attenuation, the outflowing gas is dusty. We use emission lines diagnostics to infer gas abundances within the host galaxy. The oxygen abundance is 12+log(O/H) ~ 7.95 (~18% solar) and the host is slightly nitrogen-enriched with log(N/O) ~ -0.75. Despite its extreme velocity, the mass loading factor (<0.1) and the kinematic energy of the outflow (~10^43 erg/s) suggest limited impact on star formation. The AGN component shows many similarities with little red dots (LRDs): a characteristic "V-shape", exponential profile in hydrogen lines, numerous detection of forbidden [Fe II] lines, a Balmer break, and a broad absorption feature at ~4550 {\AA}. This detection of a fast outflow in an LRD, rare in surveys dominated by low-resolution (e.g. PRISM) spectra, provides direct evidence of AGN activity in these systems.

astro-ph.GA↗

arXiv2026

SPURS: Evidence for Clumpy Neutral Envelopes and Ionized IGM Surrounding Little Red Dots in Abell 2744 from Ultra-Deep Rest-UV Spectroscopy

Rest-frame ultraviolet (UV) spectra of Little Red Dots (LRDs) often show Ly$\alpha$ emission. Along with broad Balmer emission, LRDs are expected to produce broad Ly$\alpha$ emission. However, the large column density of neutral gas invoked to explain the Balmer break should significantly redshift and further broaden the Ly$\alpha$ line, making it challenging to detect without sensitive, moderate-resolution spectra. We present ultra-deep (29 hours) G140M JWST/NIRSpec observations covering the rest-UV of two LRDs in Abell2744 from the SPURS Cycle 4 Large Program. One of our targets is Abell2744-QSO1, a gravitationally-lensed LRD at $z=7.04$ with faint UV emission (M$_{\rm UV}=-16.9$), and the other source (UNCOVER-2476) is newly-confirmed at $z=4.02$ with a very bright UV continuum (M$_{\rm UV}=-19.6$). We find that Abell2744-QSO1 has a broad Ly$\alpha$ profile, along with narrow CIV, FeII$\lambda1786$, and OI$\lambda1302$ emission. The Ly$\alpha$ profile suggests an origin similar to the broad H$\alpha$, but the line is considerably less redshifted than expected from existing dense gas models. We show that the line profile can be explained if the dense neutral gas is clumpy, allowing Ly$\alpha$ to escape by scattering off of the clump surfaces. We find that UNCOVER-2476 has narrow [NeIV] emission, indicating either a hard radiation field or shocks. We confirm two close neighbors with Ly$\alpha$ emission around Abell2744-QSO1, indicating it traces a dense environment that may have ionized its surrounding IGM. We suggest that LRDs may preferentially trace bubbles carved by their dense environments, contributing to the prevalence of Ly$\alpha$ in the population.

astro-ph.GA↗

arXiv2026

A GLIMPSE into the UV Continuum Slopes of the Faintest Galaxies in the Epoch of Reionization

As observations have yet to constrain the ionizing properties of the faintest (M$_{\rm UV}$ > -16) galaxies, their contribution to cosmic reionization remains unclear. The rest-frame ultraviolet (UV) continuum slope ($\beta$) is a powerful diagnostic of stellar populations and one of the few feasible indicators of the escape fraction of ionizing photons (f$_{\rm esc}$) for such faint galaxies at high-redshift. Leveraging ultra-deep JWST/NIRCam GLIMPSE imaging of strong lensing field Abell S1063, we estimate UV continuum slopes of 555 galaxies at z $>$ 6 with absolute magnitudes down to M$_{\rm UV}$ $\simeq -$12.5. We find a modest evolution of $\beta$ with redshift and a flattening in the $\beta$-M$_{\rm UV}$ relation such that galaxies fainter than M$_{\rm UV}$ $\sim -$16.5 no longer exhibit the bluest UV slopes. The 138 ultra-faint galaxies with M$_{\rm UV}$ $> -$16 are a diverse population encompassing dusty (30\%), old (15\%), and low-mass (50\%) galaxies. We apply the empirical $\beta$-f$_{\rm esc}$ relation from local Lyman continuum leakers, finding the mean f$_{\rm esc}$ peaks at $\sim 20\%$ at M$_{\rm UV}=-$16.5 and declines towards fainter galaxies, while remaining consistent with f$_{\rm esc}$ = 14\% within uncertainties, in agreement with recent radiative transfer simulations. Incorporating GLIMPSE constraints on the UV luminosity function, ionizing photon production efficiency, and escape fractions produces a reionization history consistent with independent observational constraints. Our results indicate galaxies with M$_{\rm UV}$ between $-18$ and $-14$ supplied $\sim 60\%$ of the ionizing photons to cosmic reionization, while the lower f$_{\rm esc}$ of fainter galaxies produces a natural cutoff in the ionizing photon production rate density.

astro-ph.GA↗

arXiv2026

GLIMPSE-D: Metallicity Decline in Faint Galaxies: Implications for [O III]+Hb Luminosity Function and Reionisation Budget

We report the measurement of the R3=[O III]5008/Hb ratios for 54 galaxies in the GLIMPSE-D survey. Thanks to gravitational lensing, our sample includes galaxies with -20 < Muv < -14 at z=6-9. We derive oxygen abundances using calibrated relationships. We observe a significant decline in R3 values below Muv > -18, which we interpret as evidence of decreasing metallicities in fainter regimes. We explore four prescription models of the evolution of R3 with UV emission based on the new measurements and results from previous surveys. Applying these models to the GLIMPSE [O III]+Hb luminosity functions, we measure and extrapolate the ionising photon production rate $\dot{N}_{ion}$ of galaxies down to very faint limits SFR(Ha) > 5e-3 Msun/yr. Our results support the dominant contribution of star-forming galaxies to reionisation, and are consistent with the recent discovery of ultra-faint metal-poor galaxies. Our measurements of the relative contribution of each luminosity bin show that galaxies with L(Ha)~1e41 to 1e42 erg/s dominate at 8<z<9, but the relative contributions become more uniform at $7<z<8$. Extreme models either under- or over-estimate the ionising photon budget, while intermediate models align with recent observational constraints.

astro-ph.GA↗

arXiv2026

A first GLIMPSE into star clusters populations across cosmic time

We present the first sample of 222 high-redshift (z>0.5) star clusters, detected with JWST/NIRCam in 78 magnified galaxies from different galaxy cluster fields. The majority of the systems (~60%) is observed in the very deep NIRCam observations of the cluster AbellS1063 (GLIMPSE program), showing the power that deep observations, combined with lensing, has to reveal these primordial stellar structures. We perform simultaneous size-flux estimates in all available NIRCam filters and spectral energy distribution (SED) fitting analysis to recover star cluster physical properties. All star cluster candidates have very high magnification. Star clusters and clumps show similar ages and redshift distributions, although noticeable differences are seen in their masses, sizes and stellar surface densities inherent to the lack of resolution in the latter group. We reconstruct the formation redshift of star clusters and find that the large majority of the observed star clusters show young ages (<100 Myr) and seems to form at cosmic noon (CN,1 1, based on a subsample of 60 star clusters younger than 100 Myr and with masses above 2e6 Msun. The star cluster mass function is well described by a power-law with slope beta = -1.89 suggesting that a power-law -2 function might already be in place in the distant Universe.

astro-ph.GA↗

arXiv2026

Relatively Fast and Reasonably Furious: Evidence for Increased Burstiness in Smaller Halos at Cosmic Dawn

We introduce an effective framework to model star-formation burstiness and use it to jointly fit galaxy UV luminosity functions (UVLFs), clustering, and H$\alpha$/UV ratios, providing the first robust empirical evidence that early galaxies hosted in lower-mass halos are burstier. Using $z\sim 4-6$ observations, we find that galaxies show approximately $0.6$ dex of SFR variability if hosted in halos of $M_h = 10^{11}\, M_\odot$ (typical of $M_{\rm UV}\approx -19$ galaxies at $z = 6$). This translates into a scatter of $\sigma_{M_{\rm UV}}\approx 0.75$ mag in the UVLF, in line with past findings. Strikingly, we find that burstiness grows for galaxies hosted in smaller halos, reaching $\gtrsim 1$ dex for $M_h \leq 10^{9}\, M_\odot$ (corresponding to $\sigma_{M_{\rm UV}} \approx 1.5$ mag for faint $M_{\rm UV} \gtrsim -15$ galaxies). Extrapolating to higher redshifts, when small halos were more prevalent, the inferred mass-dependent burstiness can reproduce observed UVLFs up to $z\sim 17$ within 1$\sigma$, potentially alleviating the tension between pre- and post-JWST galaxy-formation models. Current observations allow us to constrain the main burst timescale to approximately $20$ Myr, consistent with expectations from supernova feedback, and suggest broad distributions of ionizing efficiencies at fixed $M_{\rm UV}$. Our results demonstrate that mass-dependent burstiness, as predicted by hydrodynamical simulations, is critical for understanding the mass assembly of early galaxies.

astro-ph.GA↗

arXiv2025

An Extremely-red, UV-bright, and Extended Galaxy at z~6 in PRIMER/UDS: An Early Massive Galaxy Caught Quenching after an Obscured Starburst?

JWST continues to reveal an astonishing number of massive quiescent galaxies at $z>4$, with number densities $\gtrsim10\times$ higher than model predictions. NIRSpec spectra imply that many of these systems underwent intense starburst episodes (SFR$\,\gtrsim300M_\odot$/yr), though direct evidence of such starbursts in the Gyr largely comes from exceptionally rare dusty star-forming galaxies (DSFGs) selected in the far-infrared. Here, we report the discovery of an extremely red ($\beta=-0.6$) yet UV-bright (F115W = 26.0 mag) $z\sim6$ star-forming system selected as a Lyman-break galaxy (LBG) over $\approx$500 arcmin$^2$ of deep NIRCam imaging. This galaxy (UDS_43065) shows photometric colors implying a prominent Balmer break and strong H$\alpha$ emission, consistent with a dramatic burst of star formation (SFR$\,\approx\,500-1000\,M_\odot$/yr) occurring 5-10 Myr ago that formed 20-40% of its total stellar mass ($\approx1.5\times10^{10}M_\odot$) with little activity since. This galaxy is one of only two objects with $M_\ast>10^{10}M_\odot$ across our full sample of 813 $z\sim6$ star-forming LBGs, and the only galaxy with a confident extremely-red UV slope ($\beta>-1$). UDS_43065 is clearly resolved yet compact in F444W ($r_e=400\pm10$ pc) indicating a very high stellar mass surface density of log$(\Sigma_\mathrm{eff}/(M_\odot\,\mathrm{kpc}^{-2}))=10.25\pm0.13$ comparable to quenched $z\sim2-7$ galaxies. If the inferred star formation history (SFH) of UDS_43065 is corroborated with further observations, this object would seemingly represent a rarely-seen transitional phase between massive DSFGs and passive systems in the first Gyr, helping resolve the puzzling abundance of early massive quenched galaxies.

astro-ph.GA↗

arXiv2025

JWST's GLIMPSE: an overview of the deepest probe of early galaxy formation and cosmic reionization

We present an overview of the JWST GLIMPSE program, highlighting its survey design, primary science goals, gravitational lensing models, and first results. GLIMPSE provides ultra-deep JWST/NIRCam imaging across seven broadband filters (F090W, F115W, F200W, F277W, F356W, F444W) and two medium-band filters (F410M, F480M), with exposure times ranging from 20 to 40 hours per filter. This yields a 5$\sigma$ limiting magnitude of 30.9 AB (measured in a 0.2 arcsec diameter aperture). The field is supported by extensive ancillary data, including deep HST imaging from the Hubble Frontier Fields program, VLT/MUSE spectroscopy, and deep JWST/NIRSpec medium-resolution multi-object spectroscopy. Exploiting the strong gravitational lensing of the galaxy cluster Abell S1063, GLIMPSE probes intrinsic depths beyond 33 AB magnitudes and covers an effective source-plane area of approximately 4.4 arcmin$^2$ at $z \sim 6$. The program's central aim is to constrain the abundance of the faintest galaxies from $z \sim 6$ up to the highest redshifts, providing crucial benchmarks for galaxy formation models, which have so far been tested primarily on relatively bright systems. We present an initial sample of $\sim 540$ galaxy candidates identified at $6 < z < 16$, with intrinsic UV magnitudes spanning $M_{\mathrm UV}$ = $-$20 to $-$12. This enables unprecedented constraints on the extreme faint end of the UV luminosity function at these epochs. In addition, GLIMPSE opens new windows for spatially resolved studies of star clusters in early galaxies and the detection and characterization of faint high-$z$ active galactic nuclei. This paper accompanies the first public data release, which includes reduced JWST and HST mosaics, photometric catalogs, and gravitational lensing models.

astro-ph.GA↗

arXiv2025

Galaxy Underdensities Host the Clearest IGM Ly$\alpha$ Transmission and Indicate Anisotropic Reionization

How galaxies drive reionization and what governs its geometry remain fundamental questions. We present JWST/NIRCam wide-field slitless spectroscopy (WFSS) observations toward two of the most Ly$\alpha$-transmissive QSO sightlines near the end of reionization. We find that regions at $z \sim 5.7$ along both sightlines previously found to be low-density in Ly$\alpha$ emitters are also underdense in [O III] emitters, with densities less than half the cosmic mean. Other transmissive regions, however, are found to coincide with average-density environments, indicating that multiple pathways may produce high IGM transmission. For the first time, we measure the two-dimensional cross-correlation between IGM transmission and galaxy positions, revealing evidence for anisotropic ionization geometry. Specifically, we detect enhanced transmission at transverse distances of $\Delta r \sim 0.8$ times the mean free path, consistent with ionizing photons escaping preferentially along large-scale structures that are aligned with, but offset from, the line of sight. This anisotropic escape may contribute to the observed patchiness of reionization and challenges the assumption of isotropic ionized bubble growth in current models.

astro-ph.GA↗

arXiv2025

A GLIMPSE into the very faint-end of the H$\beta$+[OIII]$\lambda\lambda$4960,5008 luminosity function at z=7-9 behind Abell S1063

We use the ultra-deep GLIMPSE JWST/NIRCam survey to constrain the faint-end of the H$\beta$+[OIII]$\lambda\lambda$4960,5008 luminosity function (LF) down to $10^{39}$ erg/s at z=7-9 behind the lensed Hubble Frontier Field Abell S1063. We perform SED fitting on a Lyman-Break Galaxy sample, measuring combined H$\beta$+[OIII] fluxes to construct the emission-line LF. The resulting LF ($\alpha$=-1.55 to -1.78) is flatter than the UV LF ($\alpha<-2$), indicating a lower number density of low H$\beta$+[OIII] emitters at fixed MUV. We explore three explanations: (i) bursty star formation histories reducing the H$\beta$+[OIII]-to-UV ratio, (ii) metallicity effects on [OIII]/H$\beta$, or (iii) a faint-end turnover in the UV LF. Assuming an evolving [OIII]/H$\beta$ ratio, we derive a flatter [OIII]$\lambda$5008 LF ($\alpha$=-1.45 to -1.66) and a steeper H$\beta$ LF ($\alpha$=-1.68 to -1.95). The combination of decreasing metallicity and bursty star formation can reconcile the UV and H$\beta$+[OIII] LF differences. Converting the LF to the ionising photon production rate, we find that galaxies with H$\alpha$ flux $>10^{39}$ erg/s (SFR(H$\alpha$)$>5\times10^{-3} M_\odot$/yr) contribute 31%-90% and 46%-156% of the ionising photon budget at 7<z<8 and 8<z<9, respectively (for $f_{esc}=0.14$). The LF shape suggests faint galaxies contribute minimally to the ionising photon production rate. Our cosmic star formation rate density (CSFRD) estimates align with previous work, but GLIMPSE's sensitivity to low SFRs confirms that very faint galaxies are minor contributors to both the ionising photon production rate and the CSFRD. Our results suggest that GLIMPSE has detected the bulk of the total H$\beta$+[OIII] emission from star-forming galaxies, with fainter sources playing a limited role in cosmic reionisation.

astro-ph.GA↗

arXiv2025

The first GLIMPSE of the faint galaxy population at Cosmic Dawn with JWST: The evolution of the ultraviolet luminosity function across z~9-15

Using ultra-deep JWST NIRCam imaging from the GLIMPSE Survey, enhanced by gravitational lensing of the AbellS1063 cluster, we investigate the faintest galaxies ever observed in the redshift range z~9 to z~15. We identify 105 galaxy candidates within this range, spanning absolute ultraviolet (UV) magnitudes from M_UV~-18 to M_UV~-13 mag, about three magnitudes fainter, on average, than prior JWST studies. We place strong constraints on the ultra-faint end of the UV luminosity function (UVLF), finding minimal evolution in the faint-end slope, which varies from $\alpha=-2.01\pm0.20 at z=9 to \alpha=-2.10\pm0.19$ at z=13. This behaviour contrasts with the rapid evolution of the faint-end slope observed from z~0 to z~9. By integrating the UVLF down to M_UV=-16, we derive the cosmic star formation rate density (SFRD)from z=9 to z=13, revealing a best-fit redshift evolution that follows $\propto(1+z)^{-2.94^{+0.06}_{-0.10}}$. This slope is significantly shallower than predictions from most theoretical models. Extending the integration limit to M_UV=-13, we find that galaxies fainter than M_UV=-16 contribute more than 50% of the total cosmic SFR density at z~12. The observed excess in the cosmic SFRD at these high redshifts may suggest an enhancement in the star formation efficiency during the earliest phases of galaxy formation. Alternatively, this could result from other physical mechanisms, such as bursty star formation histories; minimal dust attenuation; or an evolving initial mass function. However, existing models that incorporate these scenarios fail to fully reproduce the observed redshift evolution of SFRD. Finally, we acknowledge the potential impact of low-redshift contamination and cosmic variance, as the small survey volume may not represent the broader galaxy population. Similar observations in different fields and spectroscopic confirmation are required to validate these findings

astro-ph.GA↗

arXiv2025

REBELS-MOSFIRE: Weak CIII] Emission is Typical Among Extremely UV-bright, Massive Galaxies at $z\sim7$

We present Keck/MOSFIRE H-band spectroscopic measurements covering the [CIII]1907, CIII]1909 doublet for a sample of 8 z~7 spectroscopically-confirmed star-forming galaxies drawn from the Reionization Era Bright Emission Line Survey (REBELS). This REBELS-MOSFIRE sample is notable for its bright median UV luminosity (Muv=-22.5 AB) and large median stellar mass (log(Mstar/Msun)=9.2). Although three sources show tentative evidence of a CIII] detection, we obtain no confident detections for any of the 8 REBELS-MOSFIRE sources. The median [CIII]1907+CIII]1909 3-sigma upper limit in equivalent width (EW) for the REBELS-MOSFIRE sample is 6.5 AA, and a stack of their H-band MOSFIRE spectra yields a non-detection with an associated 3-sigma upper limit of 2.6 AA. These upper limits fall significantly below the CIII] EW measured in a composite spectrum of representative z~7 star-forming galaxies, as well as those measured for notable early star-forming galaxies such as GN-z11, GHZ2, GS-z12, and RXCJ2248-ID. The lack of strong CIII] emission can be understood within the context of the stellar populations of the REBELS galaxies, as well as the ionization conditions and gas-phase metallicity implied by rest-frame optical spectroscopic properties ([OIII]+Hb EWs, and [OIII]5007/[OII]3727 and [NeIII]3869/[OII]3727 line ratios). The REBELS-MOSFIRE sample represents the higher-mass, higher-metallicity, lower-excitation tail of the z~7 galaxy population, whose ionizing properties must be fully characterized to constrain the role of star-forming galaxies during cosmic reionization.

astro-ph.GA↗

arXiv2025

COSMOS2025: The COSMOS-Web galaxy catalog of photometry, morphology, redshifts, and physical parameters from JWST, HST, and ground-based imaging

We present COSMOS2025, the COSMOS-Web catalog of photometry, morphology, photometric redshifts and physical parameters for more than 700,000 galaxies in the Cosmic Evolution Survey (COSMOS) field. This catalog is based on our \textit{James Webb Space Telescope} 255\,h COSMOS-Web program, which provides deep near-infrared imaging in four NIRCam (F115W, F150W, F277W, F444W) and one MIRI (F770W) filter over the central $\sim 0.54 {\, \rm deg}^2$ ($\sim 0.2 {\, \rm deg}^2$ for MIRI) in COSMOS. These data are combined with ground- and space-based data to derive photometric measurements of NIRCam-detected sources using both fixed-aperture photometry (on the space-based bands) and a profile-fitting technique on all 37 bands spanning 0.3-8 micron. We provide morphology for all sources from complementary techniques including profile fitting and machine-learning classification. We derive photometric redshifts, physical parameters and non-parametric star formation histories from spectral energy distribution (SED) fitting. The catalog has been extensively validated against previous COSMOS catalogs and other surveys. Photometric redshift accuracy measured using spectroscopically confirmed galaxies out to $z\sim9$ reaches $\sigma_{\rm MAD} = 0.012$ at $m_{\rm F444W}<28$ and remains at $\sigma_{\rm MAD} \lesssim 0.03$ as a function of magnitude, color, and galaxy type. This represents a factor of $\sim 2$ improvement at 26 AB mag compared to COSMOS2020. The catalog is approximately 80\% complete at $\log(M_{\star}/{\rm M}_{\odot}) \sim 9$ at $z \sim 10$ and at $\log(M_{\star}/{\rm M}_{\odot}) \sim 7$ at $z \sim 0.2$, representing a gain of 1\,dex compared to COSMOS2020. COSMOS2025 represents the definitive COSMOS-Web catalog. It is provided with complete documentation, together with redshift probability distributions, and it is ready for scientific exploitation today.

astro-ph.GA↗