Kavli Affiliate: John D. Silverman
| First 5 Authors: Si-Yue Yu, Dewang Xu, Boris S. Kalita, Sijia Li, John D. Silverman
| Summary:
We investigate the deconvolved color profiles of 223 disk galaxies at
redshifts of $z=1$-3 observed by the James Webb Space Telescope (JWST) as part
of the Cosmic Evolution Early Release Science survey (CEERS). The filters were
selected to approximate the rest-frame $B-Y$ color, which is used to identify
U-shaped color profiles — those becoming progressively bluer with increasing
radius, then turning redder beyond a specific point. We find that 36% of Type
II (down-bending) disks exhibit U-shaped color profiles with a minimum at or
near the disk break. In contrast, no Type I (single-exponential) disks and only
9% of Type III (up-bending) disks show such a profile. The presence of U-shaped
color profiles in Type II disks likely arises from the interplay between a
star-formation threshold and spiral- or bar-driven secular radial migration of
older stars outward. The fraction of Type II disks exhibiting a U-shaped color
profile remains almost consistent across two redshift bins, $z=1$-$2$ and
$z=2$-$3$, but is significantly lower than that observed in the local Universe,
likely because the secular process of radial migration at high redshift may not
have had sufficient time to significantly influence the disk structure. The
absence of U-shaped color profiles in Type II disks could point to rapid rather
than secular radial star migration potentially caused by violent clump
instabilities, transporting both younger and older stars to the outer disk. Our
results provide useful constraints on the formation and evolution models of
disk galaxies in the early Universe.
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