Abstract:

How do galaxies assemble their structures over cosmic time, and what
role does the environment play in their transformation? In this
colloquium, I present a multi-wavelength investigation into galaxy
growth over the last 7 billion years (z~1 to 0), leveraging deep
CLAUDS+HSC imaging at rest-frame UV (3000 Å) and optical (5000 Å)
wavelengths. First, I derived size-mass relations for massive
star-forming galaxies (SFGs) and quiescent galaxies (QGs) using single
Sérsic fits and examined how their sizes evolve with redshift. I found
that the size growth of SFGs is driven largely by the emergence and
expansion of their bulges, while QGs grow primarily through minor
mergers, accretion, and an influx of newly quenched "newcomer"
systems. Next, I explored the role of the environment by separating
QGs in cluster cores from those in the field. Despite the dense
cluster environment suppressing merger-driven growth and reducing
sizes through stripping, both populations show similar size-evolution
slopes. This indicates that the observed growth in clusters is
dominated by newcomers and infalling galaxies rather than internal
structural expansion. Finally, I performed bulge+disk decomposition in
both rest-frame UV and optical wavelengths, and measured size-mass
relations for each component. Bulges are consistently more compact
than disks, and the evolution of bulge-disk components is
wavelength-dependent. Bulges in quiescent galaxies show strong UV size
growth consistent with ex-situ buildup, while disks evolve more
mildly. Together, these results provide a unified view of how
galaxies—and their structural components—grow and transform from z~1
to the present, shaped by internal processes, external accretion, and
environment.