Search

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.

We present the Next Generation Deep Extragalactic Exploratory Public (NGDEEP) Survey, a deep slitless spectroscopic and imaging Cycle 1 JWST treasury survey designed to constrain feedback mechanisms in low-mass galaxies across cosmic time. NGDEEP targets the Hubble Ultra Deep Field (HUDF) with NIRISS slitless spectroscopy ( ${f}_{\mathrm{lim},\mathrm{line},5\sigma }\approx 1.2\,\times \,$ 10 ^−18 erg s ^−1 cm ^−2 ) to measure metallicities and star formation rates (SFRs) for low-mass galaxies through the peak of the cosmic SFR density (0.5 < z < 4). In parallel, NGDEEP targets the HUDF-Par2 parallel field with NIRCam ( ${m}_{\mathrm{lim},5\sigma }=30.6-30.9$ ) to discover galaxies to z > 12, constraining the slope of the faint end of the rest-ultraviolet luminosity function. NGDEEP overlaps with the deepest HST Advanced Camera for Surveys optical imaging in the sky, F435W in the HUDF ( ${m}_{\mathrm{lim},{\rm{F}}435{\rm{W}}}=29.6$ ) and F814W in HUDF-Par2 ( ${m}_{\mathrm{lim},{\rm{F}}814{\rm{W}}}=30$ ), making this a premier HST+JWST deep field. As a treasury survey, NGDEEP data are public immediately, and we will rapidly release data products and catalogs in the spirit of previous deep-field initiatives. In this paper we present the NGDEEP survey design, summarize the science goals, and detail plans for the public release of NGDEEP reduced data products.

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 analyze the evolution of massive (log _10 [ M _⋆ / M _⊙ ] > 10) galaxies at z ∼ 1–4 selected from JWST Cosmic Evolution Early Release Survey (CEERS). We infer the physical properties of all galaxies in the CEERS NIRCam imaging through spectral energy distribution (SED) fitting with dense basis to select a sample of high-redshift massive galaxies. Where available we include constraints from additional CEERS observing modes, including 18 sources with MIRI photometric coverage, and 28 sources with spectroscopic confirmations from NIRSpec or NIRCam WFSS. We sample the recovered posteriors in stellar mass from SED fitting to infer the volume densities of massive galaxies across cosmic time, taking into consideration the potential for sample contamination by active galactic nuclei. We find that the evolving abundance of massive galaxies tracks expectations based on a constant baryon conversion efficiency in dark matter halos for z ∼ 1–4. At higher redshifts, we observe an excess abundance of massive galaxies relative to this simple model, resulting in a shallower decline of observed volume densities of massive galaxies. These higher abundances can be explained by modest changes to star formation physics and/or the efficiencies with which star formation occurs in massive dark matter halos, and are not in tension with modern cosmology.

Substantial populations of massive quiescent galaxies at z ≥ 3 challenge our understanding of rapid galaxy growth and quenching over short timescales. In order to piece together this evolutionary puzzle, more statistical samples of these objects are required. Established techniques for identifying massive quiescent galaxies are increasingly inefficient and unconstrained at z > 3. As a result, studies report that as much as 70% of quiescent galaxies at z > 3 may be missed from existing surveys. In this work, we propose a new empirical color selection technique designed to select massive quiescent galaxies at 3 ≲ z ≲ 6 using JWST NIRCam imaging data. We use empirically constrained galaxy spectral energy distribution (SED) templates to define a region in the F277W − F444W versus F150W − F277W color plane that captures quiescent galaxies at z > 3. We apply these color selection criteria to the Cosmic Evolution Early Release Science (CEERS) Survey and use SED fitting on sources in the region to identify 44 candidate z ≳ 3 quiescent galaxies. Over half of these sources are newly discovered and, on average, exhibit specific star formation rates of poststarburst galaxies. Most of these sources would not be discovered using canonical UVJ diagrams. We derive volume density estimates of n ∼ 1–4 × 10 ^−5 Mpc ^−3 at 3 < z < 5, finding excellent agreement with existing reports on similar populations in the CEERS field. Thanks to NIRCam’s wavelength coverage and sensitivity, this technique provides an efficient tool to search for large samples of these rare galaxies.

The Next Generation Deep Extragalactic Exploratory Public (NGDEEP) survey program was designed specifically to include Near Infrared Slitless Spectroscopic observations (NGDEEP-NISS) to detect multiple emission lines in as many galaxies as possible and across a wide redshift range using the Near Infrared Imager and Slitless Spectrograph. We present early results obtained from the first set of observations (Epoch 1, 50% of the allocated orbits) of this program (NGDEEP-NISS1). Using a set of independently developed calibration files designed to deal with a complex combination of overlapping spectra, multiple position angles, and multiple cross filters and grisms, in conjunction with a robust and proven algorithm for quantifying contamination from overlapping dispersed spectra, NGDEEP-NISS1 has achieved a 3 σ sensitivity limit of 2 × 10 ^−18 erg s ^−1 cm ^−2 . We demonstrate the power of deep wide field slitless spectroscopy (WFSS) to characterize the star formation rates, and metallicity ([O iii ]/H β ), and dust content, of galaxies at 1 < z < 3.5. The latter showing intriguing initial results on the applicability and assumptions made regarding the use of Case B recombination. Further, we identify the presence of active galactic nuclei and infer the mass of their supermassive black holes using broadened restframe Mg ii and H β emission lines. The spectroscopic results are then compared with the physical properties of galaxies extrapolated from fitting spectral energy distribution models to photometry alone. The results clearly demonstrate the unique power and efficiency of WFSS at near-infrared wavelengths over other methods to determine the properties of galaxies across a broad range of redshifts.

We report the discovery of an accreting supermassive black hole at z = 8.679. This galaxy, denoted here as CEERS_1019, was previously discovered as a Ly α -break galaxy by Hubble with a Ly α redshift from Keck. As part of the Cosmic Evolution Early Release Science (CEERS) survey, we have observed this source with JWST/NIRSpec, MIRI, NIRCam, and NIRCam/WFSS and uncovered a plethora of emission lines. The H β line is best fit by a narrow plus a broad component, where the latter is measured at 2.5 σ with an FWHM ∼1200 km s ^−1 . We conclude this originates in the broadline region of an active galactic nucleus (AGN). This is supported by the presence of weak high-ionization lines (N V, N IV], and C III]), as well as a spatial point-source component. The implied mass of the black hole (BH) is log ( M _BH / M _⊙ ) = 6.95 ± 0.37, and we estimate that it is accreting at 1.2 ± 0.5 times the Eddington limit. The 1–8 μ m photometric spectral energy distribution shows a continuum dominated by starlight and constrains the host galaxy to be massive (log M/M _⊙ ∼9.5) and highly star-forming (star formation rate, or SFR ∼ 30 M _⊙ yr ^−1 ; log sSFR ∼ − 7.9 yr ^−1 ). The line ratios show that the gas is metal-poor ( Z / Z _⊙ ∼ 0.1), dense ( n _e ∼ 10 ^3 cm ^−3 ), and highly ionized (log U ∼ − 2.1). We use this present highest-redshift AGN discovery to place constraints on BH seeding models and find that a combination of either super-Eddington accretion from stellar seeds or Eddington accretion from very massive BH seeds is required to form this object.

We present JWST/NIRSpec prism spectroscopy of seven galaxies selected from Cosmic Evolution Early Release Science (CEERS) survey NIRCam imaging with photometric redshifts z _phot > 8. We measure emission line redshifts of z = 7.65 and 8.64 for two galaxies. For two other sources without securely detected emission lines we measure $z={9.77}_{-0.29}^{+0.37}$ and ${10.01}_{-0.19}^{+0.14}$ by fitting model spectral templates to the prism data, from which we detect continuum breaks consistent with Ly α opacity from a mostly neutral intergalactic medium. The presence of strong breaks and the absence of strong emission lines give high confidence that these two galaxies have redshifts z > 9.6, but the redshift values derived from the breaks alone have large uncertainties given the low spectral resolution and relatively low S/N of the CEERS NIRSpec prism data. The two z ∼ 10 sources observed are relatively luminous ( M _UV < −20), with blue continua (−2.3 ≲ β ≲ −1.9) and low dust attenuation ( ${A}_{V}\simeq {0.15}_{-0.1}^{+0.3}$ ); and at least one of them has a high stellar mass for a galaxy at that redshift ( $\mathrm{log}({M}_{\star }/{M}_{\odot })\simeq {9.3}_{-0.3}^{+0.2}$ ). Considered together with spectroscopic observations of other CEERS NIRCam-selected high- z galaxy candidates in the literature, we find a high rate of redshift confirmation and low rate of confirmed interlopers (8%). Ten out of 35 z > 8 candidates with CEERS NIRSpec spectroscopy do not have secure redshifts, but the absence of emission lines in their spectra is consistent with redshifts z > 9.6. We find that z > 8 photometric redshifts are generally in agreement (within their uncertainties) with the spectroscopic values, but also that the photometric redshifts tend to be slightly overestimated (〈Δ z 〉 = 0.45 ± 0.11), suggesting that current templates do not fully describe the spectra of very-high- z sources. Overall, the spectroscopy solidifies photometric redshift evidence for a high spatial density of bright galaxies at z > 8 compared to theoretical model predictions, and further disfavors an accelerated decline in the integrated UV luminosity density at z > 8.

We present JWST NIRSpec spectroscopy for 11 galaxy candidates with photometric redshifts of z ≃ 9 − 13 and M _UV ∈ [ −21, −18] newly identified in NIRCam images in the Cosmic Evolution Early Release Science Survey. We confirm emission line redshifts for 7 galaxies at z = 7.762–8.998 using spectra at ∼1–5 μ m either with the NIRSpec prism or its three medium-resolution ( R ∼ 1000) gratings. For z ≃ 9 photometric candidates, we achieve a high confirmation rate of ≃90%, which validates the classical dropout selection from NIRCam photometry. No robust emission lines are identified in three galaxy candidates at z > 10, where the strong [O iii ] and H β lines would be redshifted beyond the wavelength range observed by NIRSpec, and the Ly α continuum break is not detected with the sensitivity of the current data. Compared with Hubble Space Telescope-selected bright galaxies ( M _UV ≃ −22) that are similarly spectroscopically confirmed at z ≃ 8 − 9, these NIRCam-selected galaxies are characterized by lower star formation rates (SFRs; SFR ≃ 4 M _⊙ yr ^−1 ) and lower stellar masses (≃10 ^8 M _⊙ ), but with higher specific SFR (≃40 Gyr ^−1 ), higher [O iii ]+H β equivalent widths (≃1100 Å), and elevated production efficiency of ionizing photons ( $\mathrm{log}({\xi }_{\mathrm{ion}}/\mathrm{Hz}\,{\mathrm{erg}}^{-1})\simeq 25.8$ ) induced by young stellar populations (

We present results from the Cosmic Evolution Early Release Survey on the stellar population parameters for 28 galaxies with redshifts 4 < z < 9 using imaging data from the James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI) combined with data from the Hubble Space Telescope and the Spitzer Space Telescope. The JWST/MIRI 5.6 and 7.7 μ m data extend the coverage of the rest-frame spectral energy distribution to nearly 1 μ m for galaxies in this redshift range. By modeling the galaxies’ SEDs the MIRI data show that the galaxies have, on average, rest-frame UV (1600 Å)— I -band colors 0.4 mag bluer than derived when using photometry that lacks MIRI. Therefore, the galaxies have lower ratios of stellar mass to light. The MIRI data reduce the stellar masses by $\langle {\rm{\Delta }}\mathrm{log}{M}_{* }\rangle =0.25$ dex at 4 < z < 6 and 0.37 dex at 6 < z < 9. This also reduces the star formation rates (SFRs) by 〈ΔlogSFR〉 = 0.14 dex at 4 < z < 6 and 0.27 dex at 6 < z < 9. The MIRI data also improve constraints on the allowable stellar mass formed in early star formation. We model this using a star formation history that includes both a “burst” at z _f = 100 and a slowly varying (“delayed- τ ”) model. The MIRI data reduce the allowable stellar mass by 0.6 dex at 4 < z < 6 and by ≈1 dex at 6 < z < 9. Applying these results globally, this reduces the cosmic stellar-mass density by an order of magnitude in the early Universe ( z ≈ 9). Therefore, observations of rest-frame ≳1 μ m are paramount for constraining the stellar-mass buildup in galaxies at very high redshifts.

Lyman-break galaxy (LBG) candidates at z ≳ 10 are rapidly being identified in James Webb Space Telescope (JWST)/NIRCam observations. Due to the (redshifted) break produced by neutral hydrogen absorption of rest-frame UV photons, these sources are expected to drop out in the bluer filters while being well detected in redder filters. However, here we show that dust-enshrouded star-forming galaxies at lower redshifts ( z ≲ 7) may also mimic the near-infrared (near-IR) colors of z > 10 LBGs, representing potential contaminants in LBG candidate samples. First, we analyze CEERS-DSFG-1, a NIRCam dropout undetected in the F115W and F150W filters but detected at longer wavelengths. Combining the JWST data with (sub)millimeter constraints, including deep NOEMA interferometric observations, we show that this source is a dusty star-forming galaxy (DSFG) at z ≈ 5.1. We also present a tentative 2.6 σ SCUBA-2 detection at 850 μ m around a recently identified z ≈ 16 LBG candidate in the same field and show that, if the emission is real and associated with this candidate, the available photometry is consistent with a z ∼ 5 dusty galaxy with strong nebular emission lines despite its blue near-IR colors. Further observations on this candidate are imperative to mitigate the low confidence of this tentative submillimeter emission and its positional uncertainty. Our analysis shows that robust (sub)millimeter detections of NIRCam dropout galaxies likely imply z ∼ 4–6 redshift solutions, where the observed near-IR break would be the result of a strong rest-frame optical Balmer break combined with high dust attenuation and strong nebular line emission, rather than the rest-frame UV Lyman break. This provides evidence that DSFGs may contaminate searches for ultra-high redshift LBG candidates from JWST observations.

We present a 0.3–4.5 μ m 16-band photometric catalog for the Spitzer/HETDEX Exploratory Large-Area (SHELA) survey. SHELA covers an ∼27 deg ^2 field within the footprint of the Hobby–Eberly Telescope Dark Energy Experiment (HETDEX). Here we present new DECam imaging and an rizK _s band–selected catalog of four million sources extracted using a fully model-based approach. We validate our photometry by comparing with the model-based DECam Legacy Survey. We analyze the differences between model-based and aperture photometry by comparing with the previous SHELA catalog, finding that our model-based photometry can measure point sources to fainter fluxes and better capture the full emission of resolved sources. The catalog is 80% (50%) complete at riz ∼ 24.7 (25.1) AB mag, and the optical photometry reaches a 5 σ depth of ∼25.5 AB mag. We measure photometric redshifts and achieve a 1 σ scatter of Δ z /(1 + z ) of 0.04 with available spectroscopic redshifts at 0 ≤ z ≤ 1. This large-area, multiwavelength photometric catalog, combined with spectroscopic information from HETDEX, will enable a wide range of extragalactic science investigations.

We present Atacama Large Millimeter/submillimeter Array (ALMA) Band 7 observations of a remarkably bright galaxy candidate at ${z}_{\mathrm{phot}}={16.7}_{-0.3}^{+1.9}$ ( M _UV = −21.6), S5-z17-1, identified in James Webb Space Telescope (JWST) Early Release Observation data of Stephen’s Quintet. We do not detect the dust continuum at 866 μ m, ruling out the possibility that S5-z17-1 is a low- z dusty starburst with a star formation rate of ≳30 M _⊙ yr ^−1 . We detect a 5.1 σ line feature at 338.726 ± 0.007 GHz exactly coinciding with the JWST source position, with a 2% likelihood of the signal being spurious. The most likely line identification would be [O iii ]52 μ m at z = 16.01 or [C ii ]158 μ m at z = 4.61, whose line luminosities do not violate the nondetection of the dust continuum in both cases. Together with three other z ≳ 11–13 candidate galaxies recently observed with ALMA, we conduct a joint ALMA and JWST spectral energy distribution (SED) analysis and find that the high- z solution at z ∼ 11–17 is favored in every candidate as a very blue (UV continuum slope of ≃−2.3) and luminous ( M _UV ≃ [ − 24:−21]) system. Still, we find in several candidates that reasonable SED fits (Δ χ ^2 ≲ 4) are reproduced by type II quasar and/or quiescent galaxy templates with strong emission lines at z ∼ 3–5, where such populations predicted from their luminosity functions and EW([O iii ]+H β ) distributions are abundant in survey volumes used for the identification of the z ∼ 11–17 candidates. While these recent ALMA observation results have strengthened the likelihood of the high- z solutions, lower- z possibilities are not completely ruled out in several of the z ∼ 11–17 candidates, indicating the need to consider the relative surface densities of the lower- z contaminants in the ultra-high- z galaxy search.

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.

We present a new selection of 358 blue compact dwarf galaxies (BCDs) from 5000 square degrees in the Dark Energy Survey, and the spectroscopic follow-up of a subsample of 68 objects. For the subsample of 34 objects with deep spectra, we measure the metallicity via the direct T _e method using the auroral [O iii ] λ 4363 emission line. These BCDs have an average oxygen abundance of 12+log(O/H) = 7.8, with stellar masses between 10 ^7 and 10 ^8 M _⊙ and specific star-formation rates between ∼10 ^−9 and 10 ^−7 yr ^−1 . We compare the position of our BCDs with the mass–metallicity ( M – Z ) and luminosity–metallicity ( L – Z ) relation derived from the Local Volume Legacy sample. We find the scatter about the M – Z relation is smaller than the scatter about the L – Z relation. We identify a correlation between the offsets from the M – Z and L – Z relation that we suggest is due to the contribution of metal-poor inflows. Finally, we explore the validity of the mass–metallicity–SFR fundamental plane in the mass range probed by our galaxies. We find that BCDs with stellar masses smaller than 10 ^8 M _⊙ do not follow the extrapolation of the fundamental plane. This result suggests that mechanisms other than the balance between inflows and outflows may be at play in regulating the position of low-mass galaxies in the M – Z –SFR space.

We present a sample of 30 massive (log( M _* / M _⊙ ) > 11) z = 3–5 quiescent galaxies selected from the Spitzer-HETDEX Exploratory Large Area (SHELA) Survey and observed at 1.1 mm with Atacama Large Millimeter/submillimeter Array (ALMA) Band 6 observations. These ALMA observations would detect even modest levels of dust-obscured star formation, on the order of ∼20 M _⊙ yr ^−1 at z ∼ 4 at the 1 σ level, allowing us to quantify the amount of contamination from dusty star-forming sources in our quiescent sample. Starting with a parent sample of candidate massive quiescent galaxies from the Stevans et al. v1 SHELA catalog, we use the Bayesian B agpipes spectral energy distribution fitting code to derive robust stellar masses ( M _* ) and star formation rates (SFRs) for these sources, and select a conservative sample of 36 candidate massive ( M _* > 10 ^11 M _⊙ ) quiescent galaxies, with specific SFRs >2 σ below the Salmon et al. star-forming main sequence at z ∼ 4. Based on the ALMA imaging, six of these candidate quiescent galaxies show the presence of significant dust-obscured star formation, and thus were removed from our final sample. This implies a ∼17% contamination rate from dusty star-forming galaxies with our selection criteria using the v1 SHELA catalog. This conservatively selected quiescent galaxy sample at z = 3–5 will provide excellent targets for future observations to constrain better how massive galaxies can both grow and shut down their star formation in a relatively short period.

We report the discovery of a candidate galaxy with a photo- z of z ∼ 12 in the first epoch of the James Webb Space Telescope (JWST) Cosmic Evolution Early Release Science Survey. Following conservative selection criteria, we identify a source with a robust z _phot = ${11.8}_{-0.2}^{+0.3}$ (1 σ uncertainty) with m _F200W = 27.3 and ≳7 σ detections in five filters. The source is not detected at λ < 1.4 μ m in deep imaging from both Hubble Space Telescope (HST) and JWST and has faint ∼3 σ detections in JWST F150W and HST F160W, which signal a Ly α break near the red edge of both filters, implying z ∼ 12. This object (Maisie’s Galaxy) exhibits F115W − F200W > 1.9 mag (2 σ lower limit) with a blue continuum slope, resulting in 99.6% of the photo- z probability distribution function favoring z > 11. All data-quality images show no artifacts at the candidate’s position, and independent analyses consistently find a strong preference for z > 11. Its colors are inconsistent with Galactic stars, and it is resolved ( r _h = 340 ± 14 pc). Maisie’s Galaxy has log M _* / M _⊙ ∼ 8.5 and is highly star-forming (log sSFR ∼ −8.2 yr ^−1 ), with a blue rest-UV color ( β ∼ −2.5) indicating little dust, though not extremely low metallicity. While the presence of this source is in tension with most predictions, it agrees with empirical extrapolations assuming UV luminosity functions that smoothly decline with increasing redshift. Should follow-up spectroscopy validate this redshift, our universe was already aglow with galaxies less than 400 Myr after the Big Bang.