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The first few 100 Myr at z > 10 mark the last major uncharted epoch in the history of the universe, where only a single galaxy (GN-z11 at z ≈ 11) is currently spectroscopically confirmed. Here we present a search for luminous z > 10 galaxies with JWST/NIRCam photometry spanning ≈1–5 μm and covering 49 arcmin2 from the public JWST Early Release Science programs (CEERS and GLASS). Our most secure candidates are two M UV ≈ −21 systems: GLASS-z12 and GLASS-z10. These galaxies display abrupt ≳1.8 mag breaks in their spectral energy distributions (SEDs), consistent with complete absorption of flux bluewards of Lyα that is redshifted to z=12.4−0.3+0.1 and z=10.4−0.5+0.4 . Lower redshift interlopers such as quiescent galaxies with strong Balmer breaks would be comfortably detected at >5σ in multiple bands where instead we find no flux. From SED modeling we infer that these galaxies have already built up ∼109 solar masses in stars over the ≲300–400 Myr after the Big Bang. The brightness of these sources enable morphological constraints. Tantalizingly, GLASS-z10 shows a clearly extended exponential light profile, potentially consistent with a disk galaxy of r 50 ≈ 0.7 kpc. These sources, if confirmed, join GN-z11 in defying number density forecasts for luminous galaxies based on Schechter UV luminosity functions, which require a survey area >10× larger than we have studied here to find such luminous sources at such high redshifts. They extend evidence from lower redshifts for little or no evolution in the bright end of the UV luminosity function into the cosmic dawn epoch, with implications for just how early these galaxies began forming. This, in turn, suggests that future deep JWST observations may identify relatively bright galaxies to much earlier epochs than might have been anticipated.

We report on discovery of a concentration of massive quiescent galaxies located at z = 4. The concentration is first identified using high-quality photometric redshifts based on deep, multiband data in Subaru/XMM-Newton Deep Field. Follow-up near-infrared spectroscopic observations with MOSFIRE on Keck confirm a massive (∼1011 M ⊙) quiescent galaxy at z = 3.99. Our spectral energy distribution analyses reveal that the galaxy experienced an episode of starburst about 500 Myr prior to the observed epoch, followed by rapid quenching. Since its spectrum is sufficiently good to measure the stellar velocity dispersion, we infer its dynamical mass and find that it is consistent with its stellar mass. The galaxy is surrounded by four massive (>1010 M ⊙) quiescent galaxies on a ∼1 physical Mpc scale, all of which are consistent with being located at the same redshift based on high-accuracy spectrophotometric redshifts. This is likely a (proto)cluster dominated by quiescent galaxies, the first of the kind reported at such a high redshift as z = 4. Interestingly, it is in a large-scale structure revealed by spectroscopic redshifts from VANDELS. Furthermore, it also exhibits a red sequence, adding further support to the physical concentration of the galaxies. We find no such concentration in the Illustris-TNG300 simulation; it may be that the cluster is such a rare system that the simulation box is not sufficiently large to reproduce it. The total halo mass of the quiescent galaxies is ∼1013 M ⊙, suggesting that they form a group-sized halo once they collapse together. We discuss the implications of our findings for the quenching physics and conclude with future prospects.

We report on the spectroscopic confirmation of a massive quiescent galaxy at z spec = 4.53 in the COSMOS field. The object was first identified as a galaxy with suppressed star formation at z phot ∼ 4.65 from the COSMOS2020 catalog. The follow-up spectroscopy with Keck/MOSFIRE in the K band reveals faint [O ii] emission and the Balmer break, indicative of evolved stellar populations. We fit the spectral energy distribution using photometry and a spectrum to infer physical properties. The obtained stellar mass is high (M * ∼ 1010.8 M ⊙) and the current star formation rate is more than 1 dex below that of main-sequence galaxies at z = 4.5. Its star formation history suggests that this galaxy experienced rapid quenching from z ∼ 5. The galaxy is among the youngest quiescent galaxies confirmed so far at z spec > 3 with z form ∼ 5.2 (200 Myr ago), which is the epoch when 50% of the total stellar mass was formed. A unique aspect of the galaxy is that it is in an extremely dense region; there are four massive star-forming galaxies at 4.4 < z phot < 4.7 located within 150 physical kpc from the galaxy. Interestingly, three of them have virial radii that strongly overlap with that of the central quiescent galaxy (∼70 kpc), suggesting that the overdensity region is likely the highest-redshift candidate of a dense group with a spectroscopically confirmed quiescent galaxy at the center. The group provides us with a unique opportunity to gain insights into the role of the group environment in quenching at z ∼ 5, which corresponds to the formation epoch of massive elliptical galaxies in the local Universe.

Protoclusters of galaxies have been found in the last quarter-century. However, most of them have been found through the overdensity of star-forming galaxies, and there have been no known structures identified by more than two spectroscopically confirmed quiescent galaxies at z > 2.5. In this letter, we report the discovery of an overdense structure of massive quiescent galaxies with the spectroscopic redshift z = 2.77 in the COSMOS field, QO-1000. We first photometrically identify this structure as a 4.2σ overdensity with 14 quiescent galaxies in 7 × 4 pMpc2 from the COSMOS2020 catalog. We then securely confirm the spectroscopic redshifts of four quiescent galaxies by detecting multiple Balmer absorption lines with Keck/MOSFIRE. All the spectroscopically confirmed members are massive ( log(M⋆/M⊙)>11.0 ) and located in a narrow redshift range (2.76 < z < 2.79). Moreover, three of them are in the 1 × 1 pMpc2 in the transverse direction at the same redshift (z = 2.760–2.763). Such a concentration of four spectroscopically confirmed quiescent galaxies implies that QO-1000 is >68 times denser than the general field. In addition, we confirm that they form a red sequence in the J − K s color. This structure’s halo mass is estimated as log(Mhalo/M⊙)>13.2 from its stellar mass. Similar structures found in the IllustrisTNG simulation are expected to evolve into massive galaxy clusters with log(Mhalo/M⊙)≥14.8 at z = 0. These results suggest that QO-1000 is a more mature protocluster than the other known protoclusters. It is likely in a transition phase between star-forming protoclusters and quenched galaxy clusters.

We present the results of a systematic study of the rest-frame optical morphology of quiescent galaxies at z ≥ 3 using the Near-Infrared Camera (NIRCam) on board the James Webb Space Telescope (JWST). Based on a sample selected by UVJ color or NUVUVJ color, we focus on 26 quiescent galaxies with 9.810.3 implies that our size–stellar mass relations are below those at lower redshifts, with the amplitude of ∼0.6 kpc at M ⋆ = 5 × 1010 M ⊙. This value agrees with the extrapolation of the size evolution of quiescent galaxies at z < 3 in the literature, implying that the size of quiescent galaxies increases monotonically from z ∼ 3–5. Our sample mainly comprises galaxies with bulge-like structures according to their median Sérsic index and axis ratio of n ∼ 3–4 and q ∼ 0.6–0.8, respectively. On the other hand, there is a trend of increasing fraction of galaxies with low Sérsic index at higher redshift, suggesting 3 < z < 5 might be the epoch of onset of morphological transformation with a fraction of very notable disky quenched galaxies.

We characterize the average X-ray and radio properties of quiescent galaxies (QGs) with log(M⋆/M⊙)>10 at 0 < z < 5. QGs are photometrically selected from the latest COSMOS2020 catalog. We conduct the stacking analysis of X-ray images of the Chandra COSMOS Legacy Survey for individually undetected QGs. Thanks to the large sample and deep images, the stacked X-ray signal is significantly detected up to z ∼ 5. The average X-ray luminosity cannot be explained by the X-ray luminosity of X-ray binaries, suggesting that the low-luminosity active galactic nuclei (AGNs) ubiquitously exist in QGs. Moreover, the X-ray AGN luminosity of QGs at z > 1.5 is higher than that of star-forming galaxies (SFGs), derived in the same manner as QGs. The stacking analysis of the VLA-COSMOS images is conducted for the identical sample, and the radio signal for QGs is also detected up to z ∼ 5. We find that the radio AGN luminosity of QGs at z > 1.5 is also higher than SFGs, which is in good agreement with the X-ray analysis. The enhanced AGN activity in QGs suggested by the individual analysis in the X-ray and radio wavelength supports its important role for quenching at high redshift. Their enhanced AGN activity is less obvious at z < 1.5, which can be interpreted as an increasing role of others at lower redshifts, such as environmental quenching.

Star formation in half of massive galaxies was quenched by the time the Universe was 3 billion years old 1 . Very low amounts of molecular gas seem to be responsible for this, at least in some cases 2 – 7 , although morphological gas stabilization, shock heating or activity associated with accretion onto a central supermassive black hole are invoked in other cases 8 – 11 . Recent studies of quenching by gas depletion have been based on upper limits that are insufficiently sensitive to determine this robustly 2 – 7 , or stacked emission with its problems of averaging 8 , 9 . Here we report 1.3 mm observations of dust emission from 6 strongly lensed galaxies where star formation has been quenched, with magnifications of up to a factor of 30. Four of the six galaxies are undetected in dust emission, with an estimated upper limit on the dust mass of 0.0001 times the stellar mass, and by proxy (assuming a Milky Way molecular gas-to-dust ratio) 0.01 times the stellar mass in molecular gas. This is two orders of magnitude less molecular gas per unit stellar mass than seen in star forming galaxies at similar redshifts 12 – 14 . It remains difficult to extrapolate from these small samples, but these observations establish that gas depletion is responsible for a cessation of star formation in some fraction of high-redshift galaxies. The authors report 1.3 mm observations of dust emission from strongly lensed galaxies where star formation is quenched, demonstrating that gas depletion is responsible for the cessation of star formation in some high-redshift galaxies.

We select and characterize a sample of massive (log(M */M ⊙) > 10.6) quiescent galaxies (QGs) at 3 < z < 5 in the latest Cosmological Evolution Survey catalog (COSMOS2020). QGs are selected using a new rest-frame color-selection method, based on their probability of belonging to the quiescent group defined by a Gaussian mixture model (GMM) trained on rest-frame colors (NUV − U, U − V, V − J) of similarly massive galaxies at 2 < z < 3. We calculate the quiescent probability threshold above which a galaxy is classified as quiescent using simulated galaxies from the shark semi-analytical model. We find that, at z ≥ 3 in shark, the GMM/NUVU − VJ method outperforms classical rest-frame UVJ selection and is a viable alternative. We select galaxies as quiescent based on their probability in COSMOS2020 at 3 < z < 5, and compare the selected sample to both UVJ- and NUVrJ-selected samples. We find that, although the new selection matches UVJ and NUVrJ in number, the overlap between color selections is only ∼50%–80%, implying that rest-frame color commonly used at lower-redshift selections cannot be equivalently used at z > 3. We compute median rest-frame spectral energy distributions for our sample and find the median QG at 3 < z < 5 has a strong Balmer/4000 Å break, and residual NUV flux indicating recent quenching. We find the number densities of the entire quiescent population (including post-starbursts) more than doubles from 3.5 ± 2.2 × 10−6 Mpc−3 at 4 < z < 5 to 1.4 ± 0.4 × 10−5 Mpc−3 at 3 < z < 4, confirming that the onset of massive galaxy quenching occurs as early as 3 < z < 5.

When the light from a distant object passes very near to a foreground galaxy or cluster, gravitational lensing can cause it to appear as multiple images on the sky 1 . If the source is variable, it can be used to constrain the cosmic expansion rate 2 and dark energy models 3 . Achieving these cosmological goals requires many lensed transients with precise time-delay measurements 4 . Lensed supernovae are attractive for this purpose because they have relatively simple photometric behaviour, with well-understood light curve shapes and colours—in contrast to the stochastic variation of quasars. Here we report the discovery of a multiply imaged supernova, AT 2016jka (‘SN Requiem’). It appeared in an evolved galaxy at redshift 1.95, gravitationally lensed by a foreground galaxy cluster 5 . It is probably a type Ia supernova—the explosion of a low-mass stellar remnant, whose light curve can be used to measure cosmic distances. In archival Hubble Space Telescope imaging, three lensed images of the supernova are detected with relative time delays of <200 d. We predict that a fourth image will appear close to the cluster core in the year 2037 ± 2. Observation of the fourth image could provide a time-delay precision of ~7 d, <1% of the extraordinary 20 yr baseline. The supernova classification and the predicted reappearance time could be improved with further lens modelling and a comprehensive analysis of systematic uncertainties. The discovery of a multiply imaged, probably of type Ia, supernova in a galaxy at redshift 1.95 enables a time-delay measurement with an uncertainty of <1%. The prediction that a new image will appear in the year 2037 ± 2 allows the use of this system as a cosmological probe.

To study the role of environment in galaxy evolution, we reconstruct the underlying density field of galaxies based on COSMOS2020 (The Farmer catalog) and provide the density catalog for a magnitude-limited (K s < 24.5) sample of ∼210,000 galaxies at 0.4 < z < 5 within the COSMOS field. The environmental densities are calculated using a weighted kernel density estimation approach with the choice of a von Mises–Fisher kernel, an analog of the Gaussian kernel for periodic data. Additionally, we make corrections for the edge effect and masked regions in the field. We utilize physical properties extracted by LePhare to investigate the connection between star formation activity and the environmental density of galaxies in six mass-complete subsamples at different cosmic epochs within 0.4 < z < 4. Our findings confirm a strong anticorrelation between star formation rate (SFR)/specific SFR (sSFR) and environmental density out to z ∼ 1.1. At 1.1 < z < 2, there is no significant correlation between SFR/sSFR and density. At 2 < z < 4, we observe a reversal of the SFR/sSFR–density relation such that both SFR and sSFR increase by a factor of ∼10 with increasing density contrast, δ, from −0.4 to 5. This observed reversal at higher redshifts supports the scenario where an increased availability of gas supply, along with tidal interactions and a generally higher star formation efficiency in dense environments, could potentially enhance star formation activity in galaxies located in rich environments at z > 2.