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JWST has revealed a ubiquitous population of “little red dots” (LRDs) at z ≳ 4, selected via their red rest-frame optical emission and compact morphologies. They are thought to be reddened by dust, whether in tori of active galactic nuclei (AGNs) or the interstellar medium, though none have direct dust detections to date. Informed by the average characteristics of 675 LRDs drawn from the literature, we provide ballpark constraints on the dust characteristics of the LRD population and estimate they have average dust masses of $\langle {M}_{\mathrm{dust}}\rangle =({1.6}_{-0.9}^{+4.8})\times {10}^{4}$ M _⊙ , luminosities of $\langle {L}_{\mathrm{IR}}\rangle =({8}_{-5}^{+3})\times {10}^{10}$ L _⊙ , and temperatures of $\langle {T}_{\mathrm{dust}}\rangle ={110}_{-36}^{+21}$ K. Notably, the spectral energy distributions are thought to peak at ∼100 K (rest-frame 20–30 μ m) regardless of heating mechanism, whether AGN or star formation. LRDs’ compact sizes R _eff ∼ 100 pc are the dominant factor contributing to their low estimated dust masses. Our predictions likely mean LRDs have, on average, a submillimeter emission factor of ∼100× fainter than current Atacama Large Millimeter/submillimeter Array limits provide. The star-to-dust ratio is a factor ∼100× larger than expected from dust formation models if one assumes the rest-optical light is dominated by stars; this suggests stars do not dominate. Despite their high apparent volume density, LRDs contribute negligibly (0.1%) to the cosmic dust budget at z ≳ 4 due to their low dust masses.

We present the properties of two candidate massive ( M _⋆ ∼ 10 ^11 M _⊙ ) and dusty ( A _v > 2.5 mag) galaxies at z = 5–7 in the first 0.28 deg ^2 of the COSMOS-Web survey. One object is spectroscopically confirmed at z _spec = 5.051, while the other has a robust z _phot = 6.7 ± 0.3. Thanks to their extremely red colors (F277W–F444W ∼ 1.7 mag), these galaxies satisfy the nominal color selection for the widely studied “little red dot” (LRD) population with the exception of their spatially resolved morphologies. The morphology of our targets allows us to conclude that their red continuum is dominated by highly obscured stellar emission and not by reddened nuclear activity. Using a variety of spectral energy distribution fitting tools and star formation histories, we estimate the stellar masses to be $\mathrm{log}({M}_{\star })={11.32}_{-0.15}^{+0.07}\,{M}_{\odot }$ and $\mathrm{log}({M}_{\star })={11.2}_{-0.2}^{+0.1}\,{M}_{\odot }$ , respectively, with a red continuum emission dominated by a recent episode of star formation. We then compare their number density to the halo mass function to infer stellar baryon fractions of ϵ _⋆ ∼ 0.25 and ϵ _⋆ ∼ 0.5. Both are significantly higher than what is commonly observed in lower- z galaxies or more dust-obscured galaxies at similar redshifts. With very bright ultra-high- z Lyman-Break Galaxies and some non-AGN-dominated LRDs, such “extended” LRDs represent another population that may require very efficient star formation at early times.

We present a sample of 88 candidate z ∼ 8.5–14.5 galaxies selected from the completed NIRCam imaging from the Cosmic Evolution Early Release Science survey. These data cover ∼90 arcmin ^2 (10 NIRCam pointings) in six broadband imaging filters and one medium-band imaging filter. With this sample we confirm at higher confidence early JWST conclusions that bright galaxies in this epoch are more abundant than predicted by most theoretical models. We construct the rest-frame ultraviolet luminosity functions at z ∼ 9, 11, and 14 and show that the space density of bright ( M _UV = −20) galaxies changes only modestly from z ∼ 14 to z ∼ 9, compared to a steeper increase from z ∼ 8 to z ∼ 4. While our candidates are photometrically selected, spectroscopic follow-up has now confirmed 13 of them, with only one significant interloper, implying that the fidelity of this sample is high. Successfully explaining the evidence for a flatter evolution in the number densities of UV-bright z > 10 galaxies may thus require changes to the dominant physical processes regulating star formation. While our results indicate that significant variations of dust attenuation with redshift are unlikely to be the dominant factor at these high redshifts, they are consistent with predictions from models that naturally have enhanced star formation efficiency and/or stochasticity. An evolving stellar initial mass function could also bring model predictions into better agreement with our results. Deep spectroscopic follow-up of a large sample of early galaxies can distinguish between these competing scenarios.

The James Webb Space Telescope (JWST) has uncovered a ubiquitous population of dust-obscured compact sources at z ≳ 4. Many of these objects exhibit signs of active galactic nucleus (AGN) activity, making their study crucial for understanding the formation of supermassive black holes (SMBHs) and their growth with host galaxies. In this work, we examine low and medium-resolution JWST/NIRSpec spectra from the JADES GTO public data release in the GOODS-N field of a red, luminous ( M _B ∼ −22.2 mag) and compact ( 4000 Å) continuum of this source is strongly dominated by a massive (log _10 [ M _* / M _⊙ ] ∼ 10.6), quenched (log _10 [sSFR/yr ^−1 ] < −11) galaxy, as indicated by the clear presence of a Balmer break and stellar absorption lines. Star formation history modeling reveals a starburst episode followed by rapid quenching about 200 Myr ago. The spectrum shows extremely broad (FWHM ∼2500 km s ^−1 ) H α emission and elevated optical line ratios, indicating an actively accreting SMBH. Moreover, our work has potentially revealed clear AGN signatures in the rest-UV in little red dots for the first time via the detection of a strong Ly α emission and a broad Mg ii doublet. The derived black hole mass of log _10 ( M _BH / M _⊙ ) ∼ 7.3 results in M _BH / M _* ∼ 0.04%, consistent with the local relations, unlike the elevated ratios in other high- z reddened AGN. Finally, we use JWST data from AGN at z = 4–10 to explore an evolutionary link between high- z reddened AGN, early quiescent galaxies, and local ellipticals.

We report the identification of 15 galaxy candidates at z ≥ 9 using the initial COSMOS-Web JWST observations over 77 arcmin ^2 through four Near Infrared Camera filters (F115W, F150W, F277W, and F444W) with an overlap with the Mid-Infrared Imager (F770W) of 8.7 arcmin ^2 . We fit the sample using several publicly available spectral energy distribution (SED) fitting and photometric redshift codes and determine their redshifts between z = 9.3 and z = 10.9 (〈 z 〉 = 10.0), UV magnitudes between M _UV = −21.2 and −19.5 (with 〈 M _UV 〉 = −20.2), and rest-frame UV slopes (〈 β 〉 = −2.4). These galaxies are, on average, more luminous than most z ≥ 9 candidates discovered by JWST so far in the literature, while exhibiting similar blue colors in their rest-frame UV. The rest-frame UV slopes derived from SED fitting are blue ( β ∼ [−2.0, −2.7]) without reaching extremely blue values as reported in other recent studies at these redshifts. The blue color is consistent with models that suggest the underlying stellar population is not yet fully enriched in metals like similarly luminous galaxies in the lower-redshift Universe. The derived stellar masses with $\langle {\mathrm{log}}_{10}($ M _⋆ / M _⊙ )〉 ≈ 8–9 are not in tension with the standard Lambda cold dark matter (ΛCDM) model, and our measurement of the volume density of such UV-luminous galaxies aligns well with previously measured values presented in the literature at z ∼ 9–10. Our sample of galaxies, although compact, is significantly resolved.

We present the first results from the Web Epoch of Reionization Ly α Survey (WERLS), a spectroscopic survey of Ly α emission using Keck I/MOSFIRE and LRIS. WERLS targets bright ( J < 26) galaxy candidates with photometric redshifts of 5.5 ≲ z ≲ 8 selected from pre-JWST imaging embedded in the Epoch of Reionization (EoR) within three JWST deep fields: CEERS, PRIMER, and COSMOS-Web. Here, we report 11 z ∼ 7–8 Ly α emitters (LAEs; three secure and eight tentative candidates) detected in the first five nights of WERLS MOSFIRE data. We estimate our observed LAE yield is ∼13%, which is broadly consistent with expectations assuming some loss from redshift uncertainty, contamination from sky OH lines, and that the Universe is approximately half-ionized at this epoch, whereby observable Ly α emission is unlikely for galaxies embedded in a neutral intergalactic medium. Our targets are selected to be UV-bright, and span a range of absolute UV magnitudes with −23.1 < M _UV < −19.8. With two LAEs detected at z = 7.68, we also consider the possibility of an ionized bubble at this redshift. Future synergistic Keck+JWST efforts will provide a powerful tool for pinpointing beacons of reionization and mapping the large-scale distribution of mass relative to the ionization state of the Universe.

We report the discovery of 15 exceptionally luminous 10 ≲ z ≲ 14 candidate galaxies discovered in the first 0.28 deg ^2 of JWST/NIRCam imaging from the COSMOS-Web survey. These sources span rest-frame UV magnitudes of −20.5 > M _UV > −22, and thus constitute the most intrinsically luminous z ≳ 10 candidates identified by JWST to date. Selected via NIRCam imaging, deep ground-based observations corroborate their detection and help significantly constrain their photometric redshifts. We analyze their spectral energy distributions using multiple open-source codes and evaluate the probability of low-redshift solutions; we conclude that 12/15 (80%) are likely genuine z ≳ 10 sources and 3/15 (20%) likely low-redshift contaminants. Three of our z ∼ 12 candidates push the limits of early stellar mass assembly: they have estimated stellar masses ∼ 5 × 10 ^9 M _⊙ , implying an effective stellar baryon fraction of ϵ _⋆ ∼ 0.2−0.5, where ϵ _⋆ ≡ M _⋆ /( f _b M _halo ). The assembly of such stellar reservoirs is made possible due to rapid, burst-driven star formation on timescales < 100 Myr where the star formation rate may far outpace the growth of the underlying dark matter halos. This is supported by the similar volume densities inferred for M _⋆ ∼ 10 ^10 M _⊙ galaxies relative to M _⋆ ∼ 10 ^9 M _⊙ —both about 10 ^−6 Mpc ^−3 —implying they live in halos of comparable mass. At such high redshifts, the duty cycle for starbursts would be of order unity, which could cause the observed change in the shape of the UV luminosity function from a double power law to a Schechter function at z ≈ 8. Spectroscopic redshift confirmation and ensuing constraints of their masses will be critical to understand how, and if, such early massive galaxies push the limits of galaxy formation in the Lambda cold dark matter paradigm.

We study a new population of extremely red objects (EROs) recently discovered by the James Webb Space Telescope (JWST) based on their NIRCam colors F277W − F444W > 1.5 mag. We find 37 EROs in the Cosmic Evolution Early Release Science Survey (CEERS) field with F444W < 28 mag and photometric redshifts between 5 < z < 7, with median $z={6.9}_{-1.6}^{+1.0}$ . Surprisingly, despite their red long-wavelength colors, these EROs have blue short-wavelength colors (F150W − F200W ∼ 0 mag) indicative of bimodal spectral energy distributions (SEDs) with a red, steep slope in the rest-frame optical, and a blue, flat slope in the rest-frame UV. Moreover, all these EROs are unresolved, point-like sources in all NIRCam bands. We analyze the SEDs of eight of them with MIRI and NIRSpec observations using stellar population models and active galactic nucleus (AGN) templates. We find that dusty galaxies or obscured AGNs provide similarly good SED fits but different stellar properties: massive and dusty, $\mathrm{log}{M}_{\star }/{M}_{\odot }$ ∼ 10 and A _V ≳ 3 mag, or low mass and obscured, $\mathrm{log}{M}_{\star }/{M}_{\odot }$ ∼ 7.5 and A _V ∼ 0 mag, hosting an obscured quasi-stellar object (QSO). SED modeling does not favor either scenario, but their unresolved sizes are more suggestive of AGNs. If any EROs are confirmed to have $\mathrm{log}{M}_{\star }/{M}_{\odot }$ ≳ 10.5, it would increase the pre-JWST number density at z > 7 by up to a factor ∼60. Similarly, if they are QSOs with luminosities in the L _bol > 10 ^45–46 erg s ^−1 range, their number would exceed that of bright blue QSOs by more than three orders of magnitude. Additional photometry at mid-infrared wavelengths will reveal the true nature of the red continuum emission in these EROs and will place this puzzling population in the right context of galaxy evolution.

We present a search for extremely red, dust-obscured, z > 7 galaxies with JWST/NIRCam+MIRI imaging over the first 20 arcmin ^2 of publicly available Cycle 1 data from the COSMOS-Web, CEERS, and PRIMER surveys. Based on their red color in F277W−F444W (∼2.5 mag) and detection in MIRI/F770W (∼25 mag), we identify two galaxies, COS-z8M1 and CEERS-z7M1, that have best-fit photometric redshifts of $z={8.4}_{-0.4}^{+0.3}$ and ${7.6}_{-0.1}^{+0.1}$ , respectively. We perform spectral energy distribution fitting with a variety of codes (including bagpipes , prospector , beagle , and cigale ) and find a >95% probability that these indeed lie at z > 7. Both sources are compact ( R _eff ≲ 200 pc) and highly obscured ( A _V ∼ 1.5–2.5) and, at our best-fit redshift estimates, likely have strong [O iii ]+H β emission contributing to their 4.4 μ m photometry. We estimate stellar masses of ∼10 ^10 M _⊙ for both sources; by virtue of detection in MIRI at 7.7 μ m, these measurements are robust to the inclusion of bright emission lines, for example, from an active galactic nucleus. We identify a marginal (2.9 σ ) Atacama Large Millimeter/submillimeter Array detection at 2 mm within 0.″5 of COS-z8M1, which, if real, would suggest a remarkably high IR luminosity of ∼10 ^12 L _⊙ . These two galaxies, if confirmed at z ∼ 8, would be extreme in their stellar and dust masses and may be representative of a substantial population of highly dust-obscured galaxies at cosmic dawn.

We present the survey design, implementation, and outlook for COSMOS-Web, a 255 hr treasury program conducted by the James Webb Space Telescope in its first cycle of observations. COSMOS-Web is a contiguous 0.54 deg ^2 NIRCam imaging survey in four filters (F115W, F150W, F277W, and F444W) that will reach 5 σ point-source depths ranging ∼27.5–28.2 mag. In parallel, we will obtain 0.19 deg ^2 of MIRI imaging in one filter (F770W) reaching 5 σ point-source depths of ∼25.3–26.0 mag. COSMOS-Web will build on the rich heritage of multiwavelength observations and data products available in the COSMOS field. The design of COSMOS-Web is motivated by three primary science goals: (1) to discover thousands of galaxies in the Epoch of Reionization (6 ≲ z ≲ 11) and map reionization’s spatial distribution, environments, and drivers on scales sufficiently large to mitigate cosmic variance, (2) to identify hundreds of rare quiescent galaxies at z > 4 and place constraints on the formation of the universe’s most-massive galaxies ( M _⋆ > 10 ^10 M _⊙ ), and (3) directly measure the evolution of the stellar-mass-to-halo-mass relation using weak gravitational lensing out to z ∼ 2.5 and measure its variance with galaxies’ star formation histories and morphologies. In addition, we anticipate COSMOS-Web’s legacy value to reach far beyond these scientific goals, touching many other areas of astrophysics, such as the identification of the first direct collapse black hole candidates, ultracool subdwarf stars in the Galactic halo, and possibly the identification of z > 10 pair-instability supernovae. In this paper we provide an overview of the survey’s key measurements, specifications, goals, and prospects for new discovery.