Seeing sharper and deeper: JWST's first glimpse of the photometric and spectroscopic properties of galaxies in the epoch of reionization

We analyse the photometric and spectroscopic properties of four galaxies in the epoch of reionization (EoR) within the SMACS J0723.3-7327 JWST Early Release Observations field. Given the known spectroscopic redshifts of these sources, we investigated the accuracy with which photometric redshifts can be derived using NIRCam photometry alone, finding that F115W imaging is essential to distinguish between z ∼8 galaxies with high equivalent width (EW) [O iii] λ5007 emission and z ∼10 Balmer break galaxies. We find that all four sources exhibit strong (≥0.6 mag) F356W-F444W colours, which sit at the extreme end of theoretical predictions from numerical simulations. We find that these galaxies deviate (by ≈0.5 dex) from the local correlation between [O iii] λ5007/H β and [Ne iii] λ3869/[O ii], which is consistent with the predictions from simulations of high-redshift galaxies having elevated line-excitation ratios. We measure the [O iii] λ5007 rest-frame EWs both directly from the spectroscopy, and indirectly as inferred from the strong F356W-F444W colours, finding large [O iii] λ5007 EWs of 225-1740 Å. The [O iii] λ5007 and H β EWs are consistent with those seen in extreme, intensely star-forming dwarf galaxies in the local Universe. Our structural analysis indicates that these galaxies are resolved, exhibiting irregular shapes with bright clumps. In line with the predictions from the FLARES hydrodynamic simulations, such intense star formation and extreme nebular conditions are likely the norm, rather than the exception, in the EoR.</p

EPOCHS. II. The ultraviolet luminosity function from 7.5 < z < 13.5 Using 180 arcmin² of deep, blank fields from the PEARLS survey and public JWST data

We present an analysis of the ultraviolet luminosity function (UV LF) and star formation rate density of distant galaxies (7.5 6.5) galaxies from a consistently processed set of deep, near-infrared imaging. Within an area of 180 arcmin2, we identify 1046 candidate galaxies at redshifts z > 6.5 and we use this sample to study the UV LF in four redshift bins between 7.5 </p

First light and reionization epoch simulations (FLARES) XI: [O III] emitting galaxies at 5 < z < 10

JWST has now made it possible to probe the rest-frame optical line emission of high-redshift galaxies extending to z ≈ 9, and potentially beyond. To aid in the interpretation of these emerging constraints, in this work we explore predictions for [O III]λλ4960, 5008 Å emission in high-redshift galaxies using the First Light and Reionization Epoch Simulations (FLARES). We produce predictions for the [O III] luminosity function, its correlation with the UV luminosity, and the distribution of equivalent widths (EWs). We also explore how the [O III] EW correlates with physical properties including specific star formation rate, metallicity, and dust attenuation. Our predictions are largely consistent with recent observational constraints on the luminosity function, average EWs, and line ratios. However, they fail to reproduce the observed tail of high-EW sources and the number density of extreme line emitters. Possibilities to explain these discrepancies include an additional source of ionizing photons and/or greater stochasticity in star formation in the model or photometric scatter and/or bias in the observations. With JWST now rapidly building larger samples and a wider range of emission lines the answer to this remaining discrepancy should be available imminently.</p