Bimodal morphologies of massive galaxies at the core of a protocluster
  at z=3.09 and the strong size growth of a brightest cluster galaxy
  We present the near-infrared high resolution imaging of an extremely dense
group of galaxies at the core of the protocluster at $z=3.09$ in the SSA22
field by using the adaptive optics AO188 and the Infrared Camera and
Spectrograph (IRCS) on Subaru Telescope. Wide morphological variety of them
suggests their on-going dramatic evolutions. One of the two quiescent galaxies
(QGs), the most massive one in the group, is a compact elliptical with an
effective radius $r_{e} = 1.37\pm0.75$ kpc. It supports the two-phase formation
scenario of giant ellipticals today that a massive compact elliptical is formed
at once and evolves in the size and stellar mass by series of mergers. Since
this object is a plausible progenitor of a brightest cluster galaxy (BCG) of
one of the most massive clusters today, it requires strong size ($\ga10$) and
stellar mass ($\sim$ four times by $z=0$) growths. Another QG hosts an AGN(s)
and is fitted with a model composed from an nuclear component and S\'ersic
model. It shows spatially extended [O{\footnotesize III}]$\lambda$5007 emission
line compared to the continuum emission, a plausible evidence of outflows.
Massive star forming galaxies (SFGs) in the group are two to three times larger
than the field SFGs at similar redshift. Although we obtained the $K$-band
image deeper than the previous one, we found no candidate new members. This
implies a physical deficiency of low mass galaxies with stellar mass
$M_{\star}\la4\times10^{10}~M_{\odot}$ and/or poor detection completeness of
them owing to their diffuse morphologies.
