Extended star-forming region within galaxies in a dense proto-cluster
  core at z=2.53
  At $z\sim2$, star-formation activity is thought to be high even in
high-density environments such as galaxy clusters and proto-clusters. One of
the critical but outstanding issues is if structural growth of star-forming
galaxies can differ depending on their surrounding environments. In order to
investigate how galaxies grow their structures and what physical processes are
involved in the evolution of galaxies, one requires spatially resolved images
of not only stellar components but also star-forming regions within galaxies.
We conducted the Adaptive Optics(AO)-assisted imaging observations for
star-forming galaxies in a dense proto-cluster core at $z=2.53$ with IRCS and
AO188 mounted on the Subaru Telescope. A combination of AO and narrow-band
filters allows us to obtain resolved maps of H$\alpha$-emitting regions with an
angular resolution of 0.1--0.2~arcsec, which corresponds to $\sim1$ kpc at
$z\sim2.5$. Based on stacking analyses, we compare radial profiles of
star-forming regions and stellar components and find that the star-forming
region of a sub-sample with $\rm log(M_*/M_\odot)\sim10-11$ is more extended
than the stellar component, indicating the inside-out growth of the structure.
This trend is similar to the one for star-forming galaxies in general fields at
$z=2-2.5$ obtained with the same observational technique. Our results suggest
that the structural evolution of star-forming galaxies at $z=2-2.5$ is mainly
driven by internal secular processes irrespective of surrounding environments.
