JWST Advanced Deep Extragalactic Survey (JADES) Data Release 5: Photometrically Selected Galaxy Candidates at z > 8

TL;DR

To characterize the Cosmic Dawn galaxy population, the paper exploits DR5 JADES photometry to assemble a large sample of photometric redshift candidates with $z_{phot}>8$ across GOODS-S and GOODS-N. It adopts EAZY-py template fitting with no magnitude prior, applying criteria $z_a>8$, $S/N>5$ in at least two bands, and $\Delta \chi^2>4$ to minimize low-$z$ contamination, followed by visual vetting. The final catalog includes 2081 candidates (1597 in GOODS-S, 484 in GOODS-N) with derived $M_{UV}$ and UV slope $\beta$, plus 123 objects with spectroscopic redshifts for validation and assessment of alternative templates and Ly-$\alpha$ damping-wing absorption. The results indicate a notable fraction of morphologically extended sources up to $z\sim 13-14$ and a redshift-driven steepening of the $\beta$ vs $M_{UV}$ relation, with implications for dust content and star-formation efficiency during Cosmic Dawn, and provide a valuable resource for luminosity-function and reionization studies.

Abstract

We present a sample of 2081 sources selected at photometric redshift $z_{\mathrm{phot}} > 8$ across the JADES DR5 data release in GOODS-S and GOODS-N over a total area of 469 square arcmin. These sources range from $M_{\mathrm{UV}} = -22$ to $M_{\mathrm{UV}} = -16$, with 19 objects at $z_{\mathrm{phot}} > 14$. We estimate the UV slopes for the full sample from fits to the photometry and find evidence for a steepening of the relationship between the UV continuum slope and $M_{\mathrm{UV}}$ to higher redshifts, a result that differs from prior analyses of brighter samples in the literature. We provide evidence that over one quarter of our sources have evidence for being morphologically extended, with many galaxies showing multiple bright knots or clumps even out to $z \sim 13 - 14$, an indication of how galaxies at Cosmic Dawn are growing and evolving. We discuss JADES-GN+189.15982+62.28899, a GOODS-N F200W dropout galaxy at $z_{\mathrm{phot}} \sim 15 - 18$ which has been observed spectroscopically with JWST/NIRSpec in prism mode, resulting in a very low signal-to-noise spectrum that is consistent with the photometry and rules out a number of low-redshift solutions for the source. Finally, we use a subsample of 123 objects in our sample with spectroscopic redshifts to explore the usage of alternate fitting templates and a prescription for Ly-$α$ damping wing absorption, finding that both produce significant improvements to the estimated photometric redshifts.

Figures (2)

• Figure 1: Footprint showing the 1597 GOODS-S galaxies and candidates at $z > 8$ in our sample. We show a 5$^{\prime}$ scale bar in each panel, and in blue, the JADES-specific survey area, while we plot ancillary JWST/NIRCam data that we search over as part of JADES DR5 with a grey outline. The points are colored by their redshift, as shown in the legend in each panel. The highest density of sources are found in regions with increased observational depth, as described in the text.
• Figure 2: Footprint showing the 484 GOODS-N galaxies and candidates at $z > 8$ in our sample, with colors and lines as in Figure \ref{['fig:GS_footprint']}.