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

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 similar to 358arcmin(2) . Through conservative (8 sigma) photometric selection, we identify 341 galaxies at 5 < z < 14, with 109 having spectroscopic redshift measurements from the literature, including recent JWST NIRSpec observations. Our regression analysis reveals that the rest-frame UV size-stellar mass relation follows R-eff proportional to M-*(0.19 +/- 0.03) , similar to that of star-forming galaxies at z similar to 3, but scaled down in size by similar to 0.7 dex. We find a much slower rate for the average size evolution over the redshift range, R (eff) (SIC) (1 + z)(-0.4 +/- 0.2), than that derived in the literature. A fraction (similar to 13%) of our sample galaxies are marginally resolved even in the NIRCam imaging (less than or similar to 100 pc), located at greater than or similar to 1.5 sigma below the derived size-mass slope. These compact sources exhibit a high star formation surface density sigma SFR > 10 M (circle dot) 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 beta ratios could be high shock velocities, likely originating within intense star-forming regions characterized by high Sigma(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.