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We present the census of H  |$\beta$|  + [ |${\rm O\, {\small III}}$| ] |$4960,5008\rm{\mathring{\rm\,A}}$| emitters at |$6.8\lt z\lt 9.0$| 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 |$6.8\lt z\lt 9.0$| with observed [ |${\rm O\, {\small III}}$| ] fluxes |$f_{\rm { [{\rm O\, {\small III}}]}}\gtrsim 1\times 10^{-18}\ \rm {ergs}\ \rm {s}^{-1} \ \rm {cm}^{-2}$|⁠. The rest-frame optical line ratios of the median stacked spectrum (median |$M_{\rm {UV}}=-19.65^{+0.59}_{-1.05}$|⁠) indicate negligible dust attenuation, low metallicity (⁠|$12+\log (\rm {O/H})= 7.2-7.7$|⁠) and a high ionization parameter |$\log _{10}U \simeq -2.5$|⁠. We find a factor |$\times 1.3$| difference in the number density of |$6.8\lt z\lt 9.0$| galaxies between GOODS-South and GOODS-North, which is caused by a single overdensity at |$7.0\lt z\lt 7.2$| in GOODS-North. The bright end of the UV luminosity function of spectroscopically confirmed [ |${\rm O\, {\small III}}$| ] emitters is in good agreement with HST dropout-selected samples. Discrepancies between the observed [ |${\rm O\, {\small III}}$| ] LF, [ |${\rm O\, {\small III}}$| ]/UV ratio, and [ |${\rm O\, {\small III}}$| ] equivalent widths, and that predicted by theoretical models, suggest burstier star-formation histories and/or more heterogeneous metallicity and ionizing conditions in |$z\gt 7$| galaxies. We report a rapid decline of the [ |${\rm O\, {\small III}}$| ] luminosity density at |$z\gtrsim 6\!-\!7$| 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 |$\sim 10-20{{\ \rm per\ cent}}$| of the ionizing budget at |$z=7\!-\!8$| (assuming an escape fraction of |$10{{\ \rm per\ cent}}$|⁠), raising the prospect of directly detecting a significant fraction of the sources of reionization with JWST. [ABSTRACT FROM AUTHOR]

We report ultra-deep, medium-resolution spectroscopic observations for four quiescent galaxies with log |$_{10}(M_*/\mathrm{M_\odot })\gt 11$| at |$3 \lt z \lt 5$|⁠. These data were obtained with JWST NIRSpec as part of the Early eXtragalactic Continuum and Emission Line Science (EXCELS) survey, which we introduce in this work. The first two galaxies are newly selected from PRIMER UDS imaging, both at |$z=4.62$| and separated by 860 pkpc on the sky, within a larger structure for which we confirm several other members. Both formed at |$z\simeq 8-10$|⁠. These systems could plausibly merge by the present day to produce a local massive elliptical galaxy. The other two ultra-massive quiescent galaxies are previously known at |$z=3.99$| and 3.19, with the latter (ZF-UDS-7329) having been the subject of debate as potentially too old and too massive to be accommodated by the |$\Lambda$| -CDM halo-mass function. Both exhibit high stellar metallicities, and for ZF-UDS-7329 we are able to measure the |$\alpha -$| enhancement, obtaining [Mg/Fe] = |$0.42^{+0.19}_{-0.17}$|⁠. We finally evaluate whether these four galaxies are consistent with the |$\Lambda$| -CDM halo-mass function using an extreme value statistics approach. We find that the |$z=4.62$| objects and the |$z=3.19$| object are unlikely within our area under the assumption of standard stellar fractions (⁠|$f_*\simeq 0.1-0.2$|⁠). However, these objects roughly align with the most massive galaxies expected under the assumption of 100 per cent conversion of baryons to stars (⁠|$f_*$| =1). Our results suggest extreme galaxy formation physics during the first billion years, but no conflict with |$\Lambda$| -CDM cosmology. [ABSTRACT FROM AUTHOR]

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 |$\simeq 370$| arcmin2 of JWST /NIRCam imaging, reaching (5- |$\sigma$|⁠) depths of |$\simeq 30$| 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 |$\simeq 4$|  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 (⁠|$\rho _{\rm {SFR}}$|⁠) confirming the gradual decline deduced from early JWST studies, at least out to |$z \simeq 12$|⁠. Finally we show that the observed early evolution of the galaxy UV LF (and |$\rho _{\rm {SFR}}$|⁠) can be reproduced in a |${\rm \Lambda }$| cold dark matter Universe, with no change in dust properties or star-formation efficiency required out to |$z \simeq 12$|⁠. Instead, a progressive trend towards younger stellar population ages can reproduce the observations, and the typical ages required at |$z \simeq$| 8, 9, 10, and 11 all converge on |$\simeq 380-330$|  Myr after the big bang, indicative of a rapid emergence of early galaxies at |$z \simeq 12 - 13$|⁠. This is consistent with the first indications of a steeper drop-off in |$\rho _{\rm {SFR}}$| we find beyond |$z \simeq 13$|⁠ , possibly reflecting the rapid evolution of the halo mass function at earlier times. [ABSTRACT FROM AUTHOR]

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 z spec = 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. [ABSTRACT FROM AUTHOR]

We present a detailed study of the spatially resolved kinematics, star formation and stellar mass in a highly amplified galaxy at behind the lensing cluster MS 1358+62. We use the observed optical, near- and mid-infrared imaging from Hubble Space Telescope ACS & NICMOS and Spitzer IRAC to derive the stellar mass and the Gemini/NIFS IFU to investigate the velocity structure of the galaxy from the nebular [O ii]λλ3726.8,3728.9 emission. Using a detailed gravitational lens model, we account for lensing amplification factor 12.5 ± 2.0 and find that this intrinsically galaxy has a stellar mass of , a dynamical mass of (within of 2 kpc) and a star formation rate of . The source-plane UV/optical morphology of this galaxy is dominated by five discrete star-forming regions. Exploiting the dynamical information we derive masses for individual star-forming regions of with sizes of ∼200 pc. We find that, at a fixed size, the star formation rate density within these H ii regions is approximately two orders of magnitude greater than those observed in local spiral/starburst galaxies, but consistent with the most massive H ii regions in the local Universe such as 30 Doradus. Finally, we compare the spatially resolved nebular emission-line velocity with the Lyα and UV interstellar medium (ISM) lines and find that this galaxy is surrounded by a galactic scale outflow in which the Lyα appears redshifted by ∼150 km s−1 and the UV-ISM lines blueshifted by from the (systemic) nebular emission. The velocity structure of the outflow mirrors that of the nebular emission suggesting the outflow is young (≲15 Myr), and has yet to burst out of the system. Taken together, these results suggest that this young galaxy is undergoing its first major epoch of mass assembly. [ABSTRACT FROM AUTHOR]