Enhanced Subkiloparsec-scale Star Formation: Results from a JWST Size Analysis of 341 Galaxies at 5 < z < 14

Abstract

We present a comprehensive search and analysis of high-redshift galaxies in a suite of nine public JWST extragalactic fields taken in Cycle 1, covering a total effective search area of $\sim 358\,{\mathrm{arcmin}}^{2}$ . Through conservative (8 σ ) photometric selection, we identify 341 galaxies at 5 10 M _⊙ yr ^−1 kpc ^−2 , a range in which only <0.01% of the local star-forming galaxy sample is found. For those with available NIRSpec data, no evidence of ongoing supermassive black hole accretion is observed. A potential explanation for the observed high [O iii ]-to-H β ratios could be high shock velocities, likely originating within intense star-forming regions characterized by high Σ _SFR . Lastly, we find that the rest-frame UV and optical sizes of our sample are comparable. Our results are consistent with these early galaxies building up their structures inside out and being yet to exhibit the strong color gradient seen at lower redshift.

Keywords

• Galaxy structure
• High-redshift galaxies
• Star formation