The advent of the JWST has revolutionized our understanding of high-redshift galaxies. In particular, the NIRCam instrument on-board JWST has revealed a population of red galaxies that had largely evaded detection with Hubble Space Telescope (HST), potentially due to significant dust obscuration, quiescence, or extreme redshift. Here, we present the first NIRSpec spectra of 23 red, HST faint or dark galaxies (H-F444W>1.75), unveiling their nature and physical properties. This sample includes both dusty and quiescent galaxies with spectroscopic data from NIRSpec/PRISM, providing accurate spectroscopic redshifts with z(spec)(& horbar;)=4.1 +/- 0.7. The spectral features demonstrate that, while the majority of red galaxies are dusty, a substantial fraction, 13(-6)(+9 )%, are quiescent. For the dusty galaxies, we have quantified the dust attenuation using the Balmer decrement (H alpha/H beta), finding attenuations AV>2 mag. We find that red dusty galaxies are H alpha emitters with equivalent widths spanning the range 68A & ring;9.8. This pilot NIRSpec programme reveals the diverse nature of HST-dark galaxies and highlights the effectiveness of NIRSpec/PRISM spectroscopic follow-up in distinguishing between dusty and quiescent galaxies and properly quantifying their physical properties. Upcoming research utilizing higher-resolution NIRSpec data and combining JWST with ALMA observations will enhance our understanding of these enigmatic and challenging sources.

Feedback is the key physical mechanism regulating galaxy formation. Stars in galaxies form when baryons radiatively cool down and fall into gravitational wells. Eventually, star formation quenches as gas is depleted and/or perturbed by feedback processes, no longer being able to collapse and condense. For massive galaxies, astronomers identify feedback from accreting supermassive black holes (active galactic nuclei, AGN) as the main agent responsible for quenching. We report the first spatially resolved spectroscopic observations of a massive, completely quiescent galaxy at $z=3.714$ (Jekyll) and its neighborhood. Jekyll is part of a galaxy pair with a compact, dusty, massive star-forming companion (Hyde). We find large amounts of ionized and neutral gas in the intergalactic medium around the pair, yet Jekyll has remained quiescent for more than 500~Myr. The emitting gas is consistent with AGN photoionization, but no AGN is observed in Jekyll. We find that, in contrast to standard scenarios, AGN in satellite galaxies can be critical contributors for keeping massive galaxies quiescent in the early Universe. After the accelerated formation and quenching of the massive central galaxy, tidally induced gas stripping additionally contributes to the star-formation regulation on subsequent satellite galaxy generations.

The Hα nebular emission line is an optimal tracer for recent star formation in galaxies. With the advent of JWST, this line has recently become observable at z > 3 for the first time. We present a catalog of 1050 Hα emitters at 3.7 < z < 6.7 in the GOODS fields obtained from a blind search in JWST NIRCam/grism data. We made use of the FRESCO survey’s 124 arcmin2 of observations in GOODS-North and GOODS-South with the F444W filter, probing Hα at 4.9 < z < 6.7, and the CONGRESS survey’s 62 arcmin2 of observations in GOODS-North with F356W, probing Hα at 3.8 < z < 5.1. We found an overdensity with 98 sources at z ∼ 4.4 in GOODS-N, and confirmed previously reported overdensities at z ∼ 5.2 in GOODS-N and at z ∼ 5.4 and z ∼ 5.9 in GOODS-S. We computed the observed Hα luminosity functions (LFs) in three bins centered at z ∼ 4.45, 5.30, and 6.15, which are the first such measurements at z > 3 obtained based purely on spectroscopic data, robustly tracing galaxy star formation rates (SFRs) beyond the peak of the cosmic star formation history. We compared our results with theoretical predictions from three different simulations and found good agreement at z ∼ 4 − 6. The UV LFs of this spectroscopically confirmed sample are in good agreement with pre-JWST measurements obtained with photometrically selected objects. Finally, we derived SFR functions and integrated them to compute the evolution of the cosmic SFR densities across z ∼ 4 − 6, finding values in good agreement with recent UV estimates from Lyman-break galaxies, which imply a continuous decrease in SFR density by a factor of three over z ∼ 4 to z ∼ 6. Our work shows the power of NIRCam grism observations to efficiently provide new tests for early galaxy formation models based on emission line statistics.

ABSTRACT We present a new determination of the evolving galaxy ultraviolet (UV) luminosity function (LF) over the redshift range 9.5 < z < 12.5 based on a wide-area (>250 arcmin2) data set of JWST NIRCam near-infrared imaging assembled from 13 public JWST surveys. Our relatively large-area search allows us to uncover a sample of 61 robust z > 9.5 candidates detected at ≥8σ, and hence place new constraints on the intermediate-to-bright end of the UV LF. When combined with our previous JWST + UltraVISTA results, this allows us to measure the form of the LF over a luminosity range corresponding to four magnitudes (M1500). At these early times we find that the galaxy UV LF is best described by a double power-law function, consistent with results obtained from recent ground-based and early JWST studies at similar redshifts. Our measurements provide further evidence for a relative lack of evolution at the bright-end of the UV LF at z = 9–11, but do favour a steep faint-end slope (α ≤ −2). The luminosity-weighted integral of our evolving UV LF provides further evidence for a gradual smooth (exponential) decline in co-moving star-formation rate density (ρSFR) at least out to z ≃ 12, with our determination of ρSFR(z = 11) lying significantly above the predictions of many theoretical models of galaxy evolution.

With the advent of JWST, we can probe the rest-frame optical emission of galaxies at z> 3 with high sensitivity and spatial resolution, making it possible to accurately characterize red, optically faint galaxies and thus move towards a more complete census of the galaxy population at high redshifts. To this end, we present a sample of 148 massive, dusty galaxies from the JWST/Cosmic Evolution Early Release Science survey, colour-selected using solely JWST bands. With deep JWST/NIRCam data from 1.15 to 4.44 mu m and ancillary HST/ACS and WFC3 data, we determine the physical properties of our sample using spectral energy distribution fitting with bagpipes. We demonstrate that our selection method efficiently identifies massive ({log M-*/M-circle dot}similar to 10) and dusty ({A(V)} similar to 2,7 mag) sources, with a majority at z > 3 and predominantly lying on the galaxy main sequence. The main results of this work are the stellar mass functions (SMFs) of red, optically faint galaxies from redshifts between 3 < z < 8: these galaxies make up a significant relative fraction of the pre-JWST total SMF at 3 < z < 4 and 4< z < 6, and dominate the high-mass end of the pre-JWST SMF at 6 < z < 8, suggesting that our census of the galaxy population needs amendment at these epochs. While larger areas need to be surveyed in the future, our results suggest already that the integrated stellar mass density at log M-*/M circle dot >= 9.25 may have been underestimated in pre-JWST studies by up to similar to 15-20% at similar to 3 -6, and up to similar to 45% at z similar to 6-8, indicating the rapid onset of obscured stellar mass assembly in the early Universe.

We present the census of H beta + [O III] 4960, 5008 angstrom emitters at 6.8 < z < 9.0 from the JWST FRESCO survey over 124 arcmin(2) in the GOODS-North and GOODS-South fields. Our unbiased spectroscopic search results in 137 spectroscopically confirmed galaxies at 6.8 < z < 9.0 with observed [O III] fluxes f([O III]) greater than or similar to 1 x 10(-18) ergs s(-1) cm(-2). The rest-frame optical line ratios of the median stacked spectrum (median M-UV = - 19.65(- 1.05)(+0.59)) indicate negligible dust attenuation, low metallicity (12 + log(O/H) = 7.2 - 7.7) and a high ionization parameter log(10) U similar or equal to -2.5. We find a factor x 1.3 difference in the number density of 6.8 < z < 9.0 galaxies between GOODS-South and GOODS-North, which is caused by a single overdensity at 7.0 < z < 7.2 in GOODS-North. The bright end of the UV luminosity function of spectroscopically confirmed [O III] emitters is in good agreement with HST dropout-selected samples. Discrepancies between the observed [O III] LF, [O III]/UV ratio, and [O III] equivalent widths, and that predicted by theoretical models, suggest burstier star-formation histories and/or more heterogeneous metallicity and ionizing conditions in z > 7 galaxies. We report a rapid decline of the [O III] luminosity density at z greater than or similar to 6-7 which cannot be explained by the evolution of the cosmic star-formation rate density. Finally we find that FRESCO detects in only 2h galaxies likely accounting for similar to 10 - 20 per cent of the ionizing budget at z = 7-8 (assuming an escape fraction of 10 per cent), raising the prospect of directly detecting a significant fraction of the sources of reionization with JWST.

We present an analysis of the ultraviolet (UV) continuum slopes (beta) for a sample of 172 galaxy candidates at 8 < z(phot) < 16 selected from a combination of JWST NIRCam imaging and COSMOS/UltraVISTA ground-based near-infrared imaging. Focusing primarily on a new sample of 121 galaxies at < z > similar or equal to 11 selected from similar or equal to 320 arcmin(2) of public JWST imaging data across 15 independent data sets, we investigate the evolution of beta in the galaxy population at z >= 9. We find a significant trend between beta and redshift, with the inverse-variance weighted mean UV slope evolving from = -2.17 +/- 0.06 at z = 9.5 to = -2.59 +/- 0.06 at z = 11.5. Based on a comparison with stellar population models including nebular continuum emission, we find that at z > 10.5 the average UV continuum slope is consistent with the intrinsic blue limit of dust-free stellar populations (beta(int) similar or equal to -2.6). These results suggest that the moderately dust-reddened galaxy population at z < 10 was essentially unattenuated at z similar or equal to 11. The extremely blue galaxies being uncovered at z > 10 place important constraints on dust attenuation in galaxies in the early Universe, and imply that the already observed galaxy population is likely supplying an ionizing photon budget capable of maintaining ionized intergalactic medium fractions of greater than or similar to 5 per cent at z similar or equal to 11.

During the epoch of reionization, the first galaxies were enshrouded in pristine neutral gas, with one of the brightest emission lines in star-forming galaxies, Lyman α (Lyα), expected to remain undetected until the Universe became ionized. Providing an explanation for the surprising detection of Lyα in these early galaxies is a major challenge for extragalactic studies. Recent James Webb Space Telescope observations have reignited the debate about whether residence in an overdensity of galaxies is a sufficient and necessary condition for Lyα to escape. Here, we take unique advantage of both high-resolution and high-sensitivity images from the James Webb Space Telescope Near Infrared Camera to show that all galaxies in a sample of Lyα emitters with redshift >7 have close companions. We exploit on-the-fly radiative-transfer magnetohydrodynamical simulations with cosmic ray feedback to show that galaxies with frequent mergers have very bursty star formation histories that drives episodes of high intrinsic Lyα emission and facilitates the escape of Lyα photons along channels cleared of neutral gas. We conclude that the rapid buildup of stellar mass through mergers presents a compelling solution to the long-standing puzzle of the detection of Lyα emission deep in the epoch of reionization.

We present a new determination of the evolving galaxy ultraviolet (UV) luminosity function (LF) over the redshift range 8.5 < z < 15.5 using a combination of several major Cycle-1 JWST imaging programmes - Public Release IMaging for Extragalactic Research, JWST Advanced Deep Extragalactic Survey, and Next Generation Deep Extragalactic Exploratory Public Survey. This multifield approach yields a total of similar or equal to 370 arcmin(2) of JWST/NIRCam imaging, reaching (5-sigma) depths of similar or equal to 30 AB mag in the deepest regions. We select a sample of 2548 galaxies with a significant probability of lying at high redshift (p(z>8.5)>0.05) to undertake a statistical calculation of the UV LF. Our new measurements span similar or equal to 4 mag in UV luminosity at z = 9-12.5, placing new constraints on both the shape and evolution of the LF at early times. Our measurements yield a new estimate of the early evolution of cosmic star-formation rate density (rho SFR) confirming the gradual decline deduced from early JWST studies, at least out to z similar or equal to 12. Finally we show that the observed early evolution of the galaxy UV LF (and rho SFR) can be reproduced in a Lambda cold dark matter Universe, with no change in dust properties or star-formation efficiency required out to z similar or equal to 12. Instead, a progressive trend towards younger stellar population ages can reproduce the observations, and the typical ages required at z similar or equal to 8, 9, 10, and 11 all converge on similar or equal to 380-330 Myr after the big bang, indicative of a rapid emergence of early galaxies at z similar or equal to 12-13. This is consistent with the first indications of a steeper drop-off in rho SFR we find beyond z similar or equal to 13, possibly reflecting the rapid evolution of the halo mass function at earlier times.

Recent JWST observations have revealed an unexpected abundance of massive galaxy candidates in the early Universe, extending further in redshift and to lower luminosity than what had previously been found by sub-millimeter surveys. These JWST candidates have been interpreted as challenging the ΛCDM cosmology, but, so far, they have mostly relied only on rest-frame ultraviolet data and lacked spectroscopic confirmation of their redshifts. Here we report a systematic study of 36 massive dust-obscured galaxies with spectroscopic redshifts between z_ spec=5-9 from the JWST FRESCO survey. We find no tension with the ΛCDM model in our sample. However, three ultra-massive galaxies (logM_⋆/M_⊙ ≳11.0) require an exceptional fraction of 50 than even the most efficient galaxies at later epochs. The contribution from an active nucleus is unlikely because of their extended emission. Ultra-massive galaxies account for as much as 17 density at z∼5-6.

We utilise JWST NIRCam medium-band imaging to search for extreme redshift ($z \geq 9.5$) galaxy candidates in the Hubble Ultra Deep Field (HUDF) and the additional pointing within the GOODS-South field provided by the second NIRCam module. Our search reveals 6 robust candidates, 3 of which have recently been spectroscopically confirmed. One of these 3 is the previously controversial $z \simeq 12$ galaxy candidate UDF-22980 which is now detected in five JWST NIRCam medium-band filters (F182M, F210M, F430M, F460M and F480M), efficiently excluding alternative low-redshift solutions and allowing us to now report a secure photometric redshift of $z = 11.6 \pm 0.2$. We also detect 2 galaxies at $z \geq 12.5$ including a newly-detected candidate in the imaging provided by the second NIRCam module (south-west of the HUDF) at $z = 12.6 \pm 0.6$. We determine the physical properties of the 6 galaxies by fitting the 14-band photometry with Bagpipes. We find stellar masses of $\log(M_{\star}/{\rm {M_{\odot}}}) \simeq 7.5 - 8.7$ and star-formation rates of $\log(\rm{SFR}/M_{\odot}^{-1} \rm{yr}^{-1}) \simeq 0.3 - 5.0$. Despite the relatively small cosmological volume covered by the HUDF itself and the second NIRCam module imaging, we find that the existence of these galaxies is fully consistent with the latest measurements of both the UV luminosity function and cosmic star-formation rate density at $z\simeq11$, supporting a gradual steady decline in the cosmic star-formation rate density out to at least $z\simeq15$.

Over the last few years, both ALMA and Spitzer/IRAC observations have revealed a population of likely massive galaxies at $z>3$ that was too faint to be detected in HST rest-frame ultraviolet imaging. However, due to the very limited photometry for individual galaxies, the true nature of these so-called HST-dark galaxies has remained elusive. Here, we present the first sample of such galaxies observed with very deep, high-resolution NIRCam imaging from the Early Release Science Program CEERS. 30 HST-dark sources are selected based on their red colours across 1.6 $\mu$m to 4.4 $\mu$m. Their physical properties are derived from 12-band multi-wavelength photometry, including ancillary HST imaging. We find that these galaxies are generally heavily dust-obscured ($A_{V}\sim2$ mag), massive ($\log (M/M_{\odot}) \sim10$), star-forming sources at $z\sim2-8$ with an observed surface density of $\sim0.8$ arcmin$^{-2}$. This suggests that an important fraction of massive galaxies may have been missing from our cosmic census at $z>3$ all the way into the Reionization epoch. The HST-dark sources lie on the main sequence of galaxies and add an obscured star formation rate density (SFRD) of $\mathrm{3.2^{+1.8}_{-1.3} \times 10^{-3} M_{\odot}/yr/Mpc^{3}}$ at $z\sim7$ showing likely presence of dust in the Epoch of Reionization. Our analysis shows the unique power of JWST to reveal this previously missing galaxy population and to provide a more complete census of galaxies at $z=2-8$ based on rest-frame optical imaging.

ABSTRACT We present the JWST cycle 1 53.8 h medium program FRESCO, short for ‘First Reionization Epoch Spectroscopically Complete Observations’. FRESCO covers 62 arcmin2 in each of the two GOODS/CANDELS fields for a total area of 124 arcmin2 exploiting JWST’s powerful new grism spectroscopic capabilities at near-infrared wavelengths. By obtaining ∼2 h deep NIRCam/grism observations with the F444W filter, FRESCO yields unprecedented spectra at R ∼ 1600 covering 3.8–5.0 µm for most galaxies in the NIRCam field of view. This setup enables emission line measurements over most of cosmic history, from strong PAH lines at z ∼ 0.2–0.5, to Pa α and Pa β at z ∼ 1–3, He i and [S iii] at z ∼ 2.5–4.5, H α and [N ii] at z ∼ 5–6.5, up to [O iii] and H β for z ∼ 7–9 galaxies. FRESCO’s grism observations provide total line fluxes for accurately estimating galaxy stellar masses and calibrating slit-loss corrections of NIRSpec/MSA spectra in the same field. Additionally, FRESCO results in a mosaic of F182M, F210M, and F444W imaging in the same fields to a depth of ∼28.2 mag (5σ in 0${_{.}^{\prime\prime}}$32 diameter apertures). Here, we describe the overall survey design and the key science goals that can be addressed with FRESCO. We also highlight several, early science results, including: spectroscopic redshifts of Lyman break galaxies that were identified almost 20 yr ago, the discovery of broad-line active galactic nuclei at z > 4, and resolved Pa α maps of galaxies at z ∼ 1.4. These results demonstrate the enormous power for serendipitous discovery of NIRCam/grism observations.

ABSTRACT We reduce and analyse the available JWST ERO and ERS NIRCam imaging (SMACS0723, GLASS, CEERS) in combination with the latest deep ground-based near-infrared imaging in the COSMOS field (provided by UltraVISTA DR5) to produce a new measurement of the evolving galaxy UV luminosity function (LF) over the redshift range z = 8 − 15. This yields a new estimate of the evolution of UV luminosity density (ρUV), and hence cosmic star formation rate density (ρSFR) out to within <300 Myr of the Big Bang. Our results confirm that the high-redshift LF is best described by a double power law (rather than a Schechter) function up to z ∼ 10, and that the LF and the resulting derived ρUV (and thus ρSFR), continues to decline gradually and steadily up to z ∼ 15 (as anticipated from previous studies which analysed the pre-existing data in a consistent manner to this study). We provide details of the 61 high-redshift galaxy candidates, 47 of which are new, that have enabled this new analysis. Our sample contains 6 galaxies at z ≥ 12, one of which appears to set a new redshift record as an apparently robust galaxy candidate at z ≃ 16.4, the properties of which we therefore consider in detail. The advances presented here emphasize the importance of achieving high dynamic range in studies of early galaxy evolution, and re-affirm the enormous potential of forthcoming larger JWST programmes to transform our understanding of the young Universe.

Over the past decade, the existence of a substantial population of optically invisible, massive galaxies at $z\gtrsim3$ has been implied from mid-infrared to millimeter observations. With the unprecedented sensitivity of the JWST, such extremely massive galaxy candidates have immediately been identified even at $z>7$, in much larger numbers than expected. These discoveries raised a hot debate. If confirmed, early, high-mass galaxies challenge the current models of galaxy formation. However, the lack of spectroscopic confirmations leads to uncertain stellar mass ($M_{\star}$) estimates, and the possible presence of active galactic nuclei (AGN) adds further uncertainty. Here, we present the first sample of 36 dust-obscured galaxies with robust spectroscopic redshifts at $z_{\rm spec}=5-9$ from the JWST FRESCO survey. The three most extreme sources at $z\sim5-6$ ($\sim$1 billion years after the Big Bang) are so massive (log$M_{\star}/M_{\odot}$ $\gtrsim11.0$) that they would require, on average, about 50% of the baryons in their halos to be converted into stars -- two to three times higher than even the most efficient galaxies at later times. The extended emission of these galaxies suggests limited contribution by AGN. This population of ultra-massive galaxies accounts for 20% of the total cosmic star formation rate density at $z\sim5-6$, suggesting a substantial proportion of extremely efficient star formation in the early Universe.

ABSTRACT Before the end of the Epoch of Reionization, the Hydrogen in the Universe was predominantly neutral. This leads to a strong attenuation of Ly α lines of z ≳ 6 galaxies in the intergalactic medium. Nevertheless, Ly α has been detected up to very high redshifts (z ∼ 9) for several especially UV luminous galaxies. Here, we test to what extent the galaxy’s local environment might impact the Ly α transmission of such sources. We present an analysis of dedicated Hubble Space Telescope (HST) imaging in the CANDELS/EGS field to search for fainter neighbours around three of the most UV luminous and most distant spectroscopically confirmed Ly α emitters: EGS-zs8-1, EGS-zs8-2, and EGSY-z8p7 at zspec = 7.73, 7.48, and 8.68, respectively. We combine the multiwavelength HST imaging with Spitzer data to reliably select z ∼ 7–9 galaxies around the central, UV-luminous sources. In all cases, we find a clear enhancement of neighbouring galaxies compared to the expected number in a blank field (by a factor ∼3–9×). Our analysis thus reveals ubiquitous overdensities around luminous Ly α emitting sources in the heart of the cosmic reionization epoch. We show that our results are in excellent agreement with expectations from the Dragons simulation, confirming the theoretical prediction that the first ionized bubbles preferentially formed in overdense regions. While three UV luminous galaxies already have spectroscopic redshifts, the majority of the remaining fainter, surrounding sources are yet to be confirmed via spectroscopy. JWST follow-up observations of the neighbouring galaxies identified here will thus be needed to confirm their physical association and to map out the ionized regions produced by these sources.

This manuscript describes the public release of the Hubble Legacy Fields (HLF) project photometric catalog for the extended GOODS-South region from the Hubble Space Telescope ( HST ) archival program AR-13252. The analysis is based on the version 2.0 HLF data release that now includes all ultraviolet (UV) imaging, combining three major UV surveys. The HLF data combines over a decade worth of 7475 exposures taken in 2635 orbits totaling 6.3 Ms with the HST Advanced Camera for Surveys Wide Field Channel (ACS/WFC) and the Wide Field Camera 3 (WFC3) UVIS/IR Channels in the greater GOODS-S extragalactic field, covering all major observational efforts (e.g., GOODS, GEMS, CANDELS, ERS, UVUDF, and many other programs; see Illingworth et al.). The HLF GOODS-S catalogs include photometry in 13 bandpasses from the UV (WFC3/UVIS F225W, F275W, and F336W filters), optical (ACS/WFC F435W, F606W, F775W, F814W and F850LP filters), to near-infrared (WFC3/IR F098M, F105W, F125W, F140W and F160W filters). Such a data set makes it possible to construct the spectral energy distributions (SEDs) of objects over a wide wavelength range from high-resolution mosaics that are largely contiguous. Here, we describe a photometric analysis of 186,474 objects in the HST imaging at wavelengths 0.2–1.6 μ m. We detect objects from an ultra-deep image combining the PSF-homogenized and noise-equalized F850LP, F125W, F140W, and F160W images, including Gaia astrometric corrections. SEDs were determined by carefully taking the effects of the point-spread function in each observation into account. All of the data presented herein are available through the HLF website ( https://archive.stsci.edu/prepds/hlf/ ).