2008ApJS..175....1A

In order to reveal the rest-frame V-band morphology of galaxies at z∼3, we conducted AO-assisted K-band imaging observations of z∼3 LBGs whose absolute magnitudes range from M^*_V-0.5 mag to M^*_V+3.0 mag, with M^*_V, the characteristic absolute magnitude of z∼3 LBGs, of -24.0 mag. The AO observations resolve most LBGs at a resolution of FWHM∼0.2". The median apparent half-light radius, r_HL, is 0.23", i.e., 1.8 kpc at z=3. LBGs brighter than M^*_V have larger r_HL(0.40") than the fainter LBGs (0.23") on average, and there are no bright LBGs with a small r_HL. LBGs brighter than M^*_V have red rest-frame U-V colors (average of 0.2 mag), and most of the fainter LBGs show blue rest-frame U-V colors (average of -0.4 mag). The K-band peaks of some of the LBGs brighter than K=22.0 mag show a significant shift from those in the optical images. We fit a Sérsic profile to the images of the LBGs with K<21.5 mag, taking care of the uncertainty of the final PSFs at the position of the targets. The images of all but one LBG with K<21.5 mag are fitted well with Sérsic profiles with n indexes less than 2, similar to disk galaxies in the local universe. For the fainter LBGs, we examine the concentration parameter instead of fitting a Sérsic profile; the concentration parameters of the LBGs are consistent with those of disk galaxies. Assuming that the LBGs have a disk shape, we compared their size-luminosity and size-stellar mass relations with those of z=0 and z=1 disk galaxies. The LBGs are brighter than z=0 and z=1 disk galaxies at the same effective radius. The rest-frame V-band surface brightness of the LBGs are 2.2-2.9 mag and 1.2-1.9 mag brighter than the disk galaxies at z=0 and z=1, respectively. The size-stellar mass relation of the LBGs shows that the effective radii of the LBGs do not depend on their stellar mass. For LBGs brighter than M^*_V, the average surface stellar mass density is 3-6 times larger than those of the z=0 and z=1 disk galaxies. On the contrary, the size-stellar mass relation of the less-luminous LBGs is similar to those of z=0 and z=1 disk galaxies. We also examine the profiles of the serendipitously observed DRGs. They are fitted with Sérsic profiles with n<2, and their scatter on the C versus r_HL plane is similar to that of the z∼3 LBGs. The average surface stellar mass density of the DRGs is even larger than that of the z∼3 LBGs brighter than M^*_V. The implications of the dominance of the n<2 population among galaxies at z∼3 and the presence of the high surface stellar mass density disk systems are discussed.