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Local and low-redshift (z < 3) galaxies are known to broadly follow a bimodal distribution: actively star-forming galaxies with relatively stable star-formation rates and passive systems. These two populations are connected by galaxies in relatively slow transition. By contrast, theory predicts that star formation was stochastic at early cosmic times and in low-mass systems 1-4 . These galaxies transitioned rapidly between starburst episodes and phases of suppressed star formation, potentially even causing temporary quiescence-so-called mini-quenching events 5,6 . However, the regime of star-formation burstiness is observationally highly unconstrained. Directly observing mini-quenched galaxies in the primordial Universe is therefore of utmost importance to constrain models of galaxy formation and transformation 7,8 . Early quenched galaxies have been identified out to redshift z < 5 (refs.  9-12 ) and these are all found to be massive (M ⋆  > 10 10  M ⊙ ) and relatively old. Here we report a (mini-)quenched galaxy at z = 7.3, when the Universe was only 700 Myr old. The JWST/NIRSpec spectrum is very blue (U-V = 0.16 ± 0.03 mag) but exhibits a Balmer break and no nebular emission lines. The galaxy experienced a short starburst followed by rapid quenching; its stellar mass (4-6 × 10 8  M ⊙ ) falls in a range that is sensitive to various feedback mechanisms, which can result in perhaps only temporary quenching., (© 2024. The Author(s).)

We report measurements of the galaxy two-point correlation function at cosmic dawn, using photometrically selected sources from the JWST Advanced Deep Extragalactic Survey (JADES). The JWST/NIRCam data set comprises approximately |$N_g \simeq 7000$| photometrically selected Lyman Break Galaxies (LBGs), spanning in the redshift range |$5\le z\lt 11$|⁠. The primary objective of this study is to extend clustering measurements beyond redshift |$z\gt 10$|⁠ , finding a galaxy bias |$b=9.6\pm 1.7$| for the sample at |$\overline{z} = 10.6$|⁠. The result suggests that the observed sources are hosted by dark matter haloes of approximately |$M_{h}\sim 10^{10.6}~\mathrm{{\rm M}_{\odot }}$|⁠ , in broad agreement with theoretical and numerical modelling of early galaxy formation during the epoch of reionization. Furthermore, the JWST JADES data set enables an unprecedented investigation of clustering of dwarf galaxies two orders of magnitude fainter than the characteristic |$L_*$| luminosity (i.e. with |$M_{F200W}\simeq -15.8$|⁠) during the late stages of the epoch of reionization at |$z\sim 6$|⁠. By analysing clustering as a function of luminosity, we find that |$b(M_{F200W})$| aligns with previous results for brighter galaxies and then decreases with |$M_{F200W}$|⁠ , as theoretically expected for fainter candidates. These initial results demonstrate the potential for further quantitative characterization of the interplay between assembly of dark matter and light during cosmic dawn that the growing samples of JWST observations are enabling. [ABSTRACT FROM AUTHOR]

JWST has recently sparked a new era of Lyα spectroscopy, delivering the first measurements of the Lyα escape fraction and velocity profile in typical galaxies at z ≃ 6−10. These observations offer new prospects for insight into the earliest stages of reionization. But to realize this potential, we need robust models of Lyα properties in galaxies at z ≃ 5−6 when the IGM is mostly ionized. Here, we use new JWST observations from the JADES and FRESCO surveys combined with VLT/MUSE and Keck/DEIMOS data to characterize statistical distributions of Lyα velocity offsets, escape fractions, and EWs in z ≃ 5−6 galaxies. We find that galaxies with large Lyα escape fractions (>0.2) are common at z ≃ 5−6, comprising 30 per cent of Lyman break selected samples. Comparing to literature studies, our census suggests that Lyα becomes more prevalent in the galaxy population towards higher redshift from z ∼ 3 to z ∼ 6, although we find that this evolution slows considerably between z ∼ 5 and z ∼ 6, consistent with modest attenuation from residual H i in the mostly ionized IGM at z ≃ 5−6. We find significant evolution in Lyα velocity profiles between z ≃ 2−3 and z ≃ 5−6, likely reflecting the influence of resonant scattering from residual intergalactic H i on the escape of Lyα emission near line centre. This effect will make it challenging to use Lyα peak offsets as a probe of Lyman continuum leakage at z ≃ 5−6. We use our z ≃ 5−6 Lyα distributions to make predictions for typical Lyα properties at z ≳ 8 and discuss implications of a recently discovered Lyα emitter at z ≃ 8.5 with a small peak velocity offset (156 km s−1). [ABSTRACT FROM AUTHOR]

We investigate the incidence and properties of ionised gas outflows in a sample of 52 galaxies with stellar masses between 107M⊙ and 109M⊙ observed with ultra-deep JWST/NIRSpec MSA spectroscopy as part of the JWST Advanced Deep Extragalactic Survey (JADES). The high-spectral resolution (R2700) NIRSpec observations allowed us to identify for the first time the potential signature of outflows in the rest-frame optical nebular lines in low-mass galaxies at z > 4. The incidence fraction of ionised outflows, traced by broad components, is about 25–40%, depending on the intensity of the emission lines. The low incidence fraction might be due to both the sensitivity limit and the fact that outflows are not isotropic, but have a limited opening angle, which only results in detection when this is directed toward our line of sight. Evidence for outflows increases slightly with stellar mass and star formation rate. The median velocity and mass-loading factor (i.e. the ratio of the mass outflow rate and star formation rate) of the outflowing ionised gas are 350 km s−1 and η = 2.0−1.5+1.6, respectively. These are 1.5 and 100 times higher than the typical values observed in local dwarf galaxies. Some of these high-redshift outflows can escape the gravitational potential of the galaxy and dark matter halo and enrich the circumgalactic medium and possibly even the intergalactic medium. Our results indicate that outflows can significantly impact the star formation activity in low-mass galaxies within the first 2 Gyr of the Universe. [ABSTRACT FROM AUTHOR]

We present a study of the environments of 17 Lyman-α emitting galaxies (LAEs) in the reionisation-era (5.8 < z < 8) identified by JWST/NIRSpec as part of the JWST Advanced Deep Extragalactic Survey (JADES). Unless situated in sufficiently (re)ionised regions, Lyman-α emission from these galaxies would be strongly absorbed by neutral gas in the intergalactic medium (IGM). We conservatively estimate sizes of the ionised regions required to reconcile the relatively low Lyman-α velocity offsets (ΔvLyα < 300 km s−1) with moderately high Lyman-α escape fractions (fesc, Lyα > 5%) observed in our sample of LAEs, suggesting the presence of ionised hydrogen along the line of sight towards at least eight out of 17 LAEs. We find minimum physical 'bubble' sizes of the order of Rion ∼ 0.1–1 pMpc are required in a patchy reionisation scenario where ionised bubbles containing the LAEs are embedded in a fully neutral IGM. Around half of the LAEs in our sample are found to coincide with large-scale galaxy overdensities seen in FRESCO at z ∼ 5.8–5.9 and z ∼ 7.3, suggesting Lyman-α transmission is strongly enhanced in such overdense regions, and underlining the importance of LAEs as tracers of the first large-scale ionised bubbles. Considering only spectroscopically confirmed galaxies, we find our sample of UV-faint LAEs (MUV ≳ −20 mag) and their direct neighbours are generally not able to produce the required ionised regions based on the Lyman-α transmission properties, suggesting lower-luminosity sources likely play an important role in carving out these bubbles. These observations demonstrate the combined power of JWST multi-object and slitless spectroscopy in acquiring a unique view of the early Universe during cosmic reionisation via the most distant LAEs. [ABSTRACT FROM AUTHOR]

We present images and a multiwavelength photometric catalog based on all of the JWST NIRCam observations obtained to date in the region of the Abell 2744 galaxy cluster. These data come from three different programs, namely, the GLASS-JWST Early Release Science Program, UNCOVER, and the Director's Discretionary Time program 2756. The observed area in the NIRCam wide-band filters—covering the central and extended regions of the cluster, as well as new parallel fields—is 46.5 arcmin2 in total. All images in eight bands (F090W, F115W, F150W, F200W, F277W, F356W, F410M, and F444W) have been reduced adopting the latest calibration and reference files available. Data reduction has been performed using an augmented version of the official JWST pipeline, with improvements aimed at removing or mitigating defects in the raw images and improving the background subtraction and photometric accuracy. We obtain an F444W-detected multiband catalog, including all NIRCam and available Hubble Space Telescope data, adopting forced-aperture photometry on point-spread-function-matched images. The catalog is intended to enable early scientific investigations and is optimized for the study of faint galaxies; it contains 24,389 sources, with a 5 σ limiting magnitude in the F444W band ranging from 28.5 AB to 30.5 AB, as a result of the varying exposure times of the surveys that observed the field. We publicly release the reduced NIRCam images, associated multiwavelength catalog, and the code adopted for 1/ f noise removal with the aim of aiding users in familiarizing themselves with JWST NIRCam data and identifying suitable targets for follow-up observations. [ABSTRACT FROM AUTHOR]

We present a detailed analysis of the rest-frame optical emission line ratios for three spectroscopically confirmed galaxies at z > 7.5. The galaxies were identified in the James Webb Space Telescope (JWST) Early Release Observations field SMACS J0723.3 − 7327. By quantitatively comparing Balmer and oxygen line ratios of these galaxies with various low-redshift 'analogue' populations (e.g. Green Peas, Blueberries, etc.), we show that no single analogue population captures the diversity of line ratios of all three galaxies observed at z > 7.5. We find that S06355 at z  = 7.67 and S10612 at z  = 7.66 are similar to local Green Peas and Blueberries. In contrast, S04590 at z  = 8.50 appears to be significantly different from the other two galaxies, most resembling extremely low-metallicity systems in the local Universe. Perhaps the most striking spectral feature in S04590 is the curiously high [O  iii ] λ4363/[O  iii ] λ5007 ratio (RO3) of 0.048 (or 0.055 when dust-corrected), implying either extremely high electron temperatures, >3 × 104 K, or gas densities >104 cm−3. Observed line ratios indicate that this galaxy is unlikely to host an AGN. Using photoionization modelling, we show that the inclusion of high-mass X-ray binaries or a high cosmic ray background in addition to a young, low-metallicity stellar population can provide the additional heating necessary to explain the observed high RO3 while remaining consistent with other observed line ratios. Our models represent a first step at accurately characterizing the dominant sources of photoionization and heating at very high redshifts, demonstrating that non-thermal processes may become important as we probe deeper into the Epoch of Reionization. [ABSTRACT FROM AUTHOR]

We determine the [O III]λ5007 equivalent width (EW) distribution of |$1.700\lt \rm {z}\lt 2.274$| rest-frame ultraviolet (UV)-selected (MUV < −19) star-forming galaxies in the GOODS North and South fields. We make use of deep HDUV broad-band photometry catalogues for selection and 3D- HST WFC3/IR grism spectra for measurement of line properties. The [O III]λ5007 EW distribution allows us to measure the abundance of extreme emission line galaxies (EELGs) within this population. We model a lognormal distribution to the [O III]λ5007 rest-frame EWs of galaxies in our sample, with location parameter μ = 4.24 ± 0.07 and variance parameter σ = 1.33 ± 0.06. This EW distribution has a mean [O III]λ5007 EW of 168 ± 1 Å. The fractions of |$\rm {z}\sim 2$| rest-UV-selected galaxies with [O III]λ5007 EWs greater than 500, 750, and 1000 Å are measured to be |$6.8^{+1.0}_{-0.9}{{\ \rm per\ cent}}$|⁠ , |$3.6^{+0.7}_{-0.6}{{\ \rm per\ cent}}$|⁠ , and |$2.2^{+0.5}_{-0.4}{{\ \rm per\ cent}}$|⁠ , respectively. The EELG fractions do not vary strongly with UV luminosity in the range (−21.6 < M UV < −19.0) considered in this paper, consistent with findings at higher redshifts. We compare our results to |$\rm {z}\sim 5$| and |$\rm {z}\sim 7$| studies, where candidate EELGs have been discovered through Spitzer /IRAC colours, and we identify rapid evolution with redshift in the fraction of star-forming galaxies observed in an extreme emission line phase (a rise by a factor ∼10 between |$\rm {z}\sim 2$| and |$\rm {z}\sim 7$|⁠). This evolution is consistent with an increased incidence of strong bursts in the galaxy population of the reionization era. While this population makes a sub-dominant contribution of the ionizing emissivity at |$\rm {z}\simeq 2$|⁠ , EELGs are likely to dominate the ionizing output in the reionization era. [ABSTRACT FROM AUTHOR]