Adaptive optics rest-frame V-band imaging of lyman break galaxies at z ∼ 3: High surface density disklike galaxies?

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 atz = 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 rHL. 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.