MOIRCS Deep Survey. VII: NIR Morphologies of Star-forming Galaxies at
  Redshift z~1
  We investigate rest-frame near-infrared (NIR) morphologies of a sample of 139
galaxies with M_{s} >= 1 x 10^{10} M_{sun} at z=0.8-1.2 in the GOODS-North
field using our deep NIR imaging data (MOIRCS Deep Survey, MODS). We focus on
Luminous Infrared Galaxies (LIRGs), which dominate high star formation rate
(SFR) density at z~1, in the sample identified by cross-correlating with the
Spitzer/MIPS 24um source catalog. We perform two-dimensional light profile
fitting of the z~1 galaxies in the Ks-band (rest-frame J-band) with a single
component Sersic model. We find that at z~1, ~90% of LIRGs have low Sersic
indices (n<2.5, similar to disk-like galaxies) in the Ks-band, and those
disk-like LIRGs consist of ~60% of the whole disk-like sample above M_{s} >= 3
x 10^{10} M_{sun}. The z~1 disk-like LIRGs are comparable or ~20% small at a
maximum in size compared to local disk-like galaxies in the same stellar mass
range. If we examine rest-frame UV-optical morphologies using the HST/ACS
images, the rest-frame B-band sizes of the z~1 disk-like galaxies are
comparable to those of the local disk-like galaxies as reported by previous
studies on size evolution of disk-like galaxies in the rest-frame optical band.
Measuring color gradients (galaxy sizes as a function of wavelength) of the z~1
and local disk-like galaxies, we find that the z~1 disk-like galaxies have 3-5
times steeper color gradient than the local ones. Our results indicate that (i)
more than a half of relatively massive disk-like galaxies at z~1 are in violent
star formation epochs observed as LIRGs, and also (ii) most of those LIRGs are
constructing their fundamental disk structure vigorously. The high SFR density
in the universe at z~1 may be dominated by such star formation in disk region
in massive galaxies.
