What determines the sizes of red early-type galaxies?
  The sizes of galaxies are known to be closely related with their masses,
luminosities, redshifts and morphologies. However, when we fix these quantities
and morphology, we still find large dispersions in the galaxy size
distribution. We investigate the origin of these dispersions for red early-type
galaxies, using two SDSS-based catalogs. We find that the sizes of faint
galaxies (log(M_dyn/M_sun) < 10.3 or M_r > -19.5, where M_r is the r-band
absolute magnitude, k-corrected to z = 0.1) are affected more significantly by
luminosity, while the sizes of bright galaxies (log(M_dyn/M_sun) > 11.4 or M_r
< -21.4) are by dynamical mass. At fixed mass and luminosity, the sizes of
low-mass galaxies (log(M_dyn/M_sun) ~ 10.45 and M_r ~ -19.8) are relatively
less sensitive to their colors, color gradients and axis ratios. On the other
hand, the sizes of intermediate-mass (log(M_dyn/M_sun) ~ 10.85 and M_r ~ -20.4)
and high-mass (log(M_dyn/M_sun) ~ 11.25 and M_r ~ -21.0) galaxies significantly
depend on those parameters, in the sense that larger red early-type galaxies
have bluer colors, more negative color gradients (bluer outskirts) and smaller
axis ratios. These results indicate that the sizes of intermediate- and
high-mass red early-type galaxies are significantly affected by their recent
minor mergers or rotations, whereas the sizes of low-mass red early-type
galaxies are affected by some other mechanisms. Major dry mergers also seem to
have influenced on the size growth of high-mass red early-type galaxies.
