Morphologies of Galaxies at $z \gtrsim 9$ Uncovered by JWST/NIRCam Imaging: Cosmic Size Evolution and an Identification of an Extremely Compact Bright Galaxy at $z\sim 12$

Understand

We present morphologies of galaxies at $z \gtrsim 9$ resolved by JWST/NIRCam $2$-$5\mu$m imaging.

• Our sample consists of $22$ galaxy candidates identified by stringent dropout and photo-$z$ criteria in GLASS, CEERS, SMACS J0723, and Stephan's Quintet flanking fields, one of which has been spectroscopically identified at $z=11.44$.
• We perform surface brightness (SB) profile fitting with GALFIT for $6$ bright galaxies with S/N $=10$-$40$ on an individual basis and for stacked faint galaxies with secure point-spread functions (PSFs) of the NIRCam real data, carefully evaluating systematics by Monte-Carlo simulations.
• We compare our results with those of previous JWST studies, and confirm that effective radii $r_{\rm e}$ of our measurements are consistent with those of previous measurements at $z\sim 9$.