We report the multi-wavelength identification of the X-ray sources found in the Subaru-XMM-Newton Deep Survey (SXDS) using deep imaging data covering the wavelength range between the far-UV to the mid-IR. We select a primary counterpart of each X-ray
source by applying the likelihood ratio method to R-band, 3.6micron, near-UV, and 24micron source catalogs as well as matching catalogs of AGN candidates selected in 1.4GHz radio and i-band variability surveys. Once candidates of Galactic stars, ultra-luminous X-ray sources in a nearby galaxy, and clusters of galaxies are removed there are 896 AGN candidates in the sample. We conduct spectroscopic observations of the primary counterparts with multi-object spectrographs in the optical and NIR; 65% of the X-ray AGN candidates are spectroscopically-identified. For the remaining X-ray AGN candidates, we evaluate their photometric redshift with photometric data in 15 bands. Utilising the multi-wavelength photometric data of the large sample of X-ray selected AGNs, we evaluate the stellar masses, M*, of the host galaxies of the narrow-line AGNs. The distribution of the stellar mass is remarkably constant from z=0.1 to 4.0. The relation between M* and 2--10 keV luminosity can be explained with strong cosmological evolution of the relationship between the black hole mass and M*. We also evaluate the scatter of the UV-MIR spectral energy distribution (SED) of the X-ray AGNs as a function of X-ray luminosity and absorption to the nucleus. The scatter is compared with galaxies which have redshift and stellar mass distribution matched with the X-ray AGN. The UV-NIR SEDs of obscured X-ray AGNs are similar to those of the galaxies in the matched sample. In the NIR-MIR range, the median SEDs of X-ray AGNs are redder, but the scatter of the SEDs of the X-ray AGN broadly overlaps that of the galaxies in the matched sample.
In order to investigate the growth of super-massive black holes (SMBHs), we construct the black hole mass function (BHMF) and Eddington ratio distribution function (ERDF) of X-ray-selected broad-line AGNs at z~1.4 in the Subaru XMM-Newton Deep Survey
field. In this redshift range, a significant part of the accretion growth of SMBHs is thought to be taking place. Black hole masses of X-ray-selected broad-line AGNs are estimated using the width of the broad MgII line and the 3000A monochromatic luminosity. We supplement the MgII FWHM values with the Ha FWHM obtained from our NIR spectroscopic survey. Using the black hole masses of broad-line AGNs at redshifts between 1.18 and 1.68, the binned broad-line AGN BHMF and ERDF are calculated using the Vmax method. To properly account for selection effects that impact the binned estimates, we derive the corrected broad-line AGN BHMF and ERDF by applying the Maximum Likelihood method, assuming that the ERDF is constant regardless of the black hole mass. We do not correct for the non-negligible uncertainties in virial BH mass estimates. If we compare the corrected broad-line AGN BHMF with that in the local Universe, the corrected BHMF at z~1.4 has a higher number density above 10^8 Msolar but a lower number density below that mass range. The evolution may be indicative of a down-sizing trend of accretion activity among the SMBH population. The evolution of broad-line AGN ERDF from z=1.4 to 0 indicates that the fraction of broad-line AGNs with accretion rate close to the Eddington-limit is higher at higher redshifts.
In order to reveal the stellar mass distribution of z~3 galaxies, we are conducting deep imaging observations of U-dropout Lyman Break Galaxies (LBGs) with Adaptive Optics (AO) systems in K-band, which corresponds to rest-frame V-band of z~3 galaxies
. The results of the Subaru intensive-program observations with AO36/NGS/IRCS indicate that 1) the K-band peaks of some of the LBGs brighter than K=22.0 mag show significant offset from those in the optical images, 2) the z~3 Mv* LBGs and serendipitously observed Distant Red Galaxies (DRGs) have flat profiles similar to disk galaxies in the local universe (i.e., Sersic with n<2), and 3) the surface stellar mass densities of the Mv* LBGs are 3-6 times larger than those of disk galaxies at z=0-1. Considering the lack of n>2 systems among the luminous z~3 LBGs and DRGs, and their strong spatial clustering, we infer that the dense n<2 disk-like structures evolve into the n>2 spheroids of nearby galaxies through relaxations due to major merger events.
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 with Mv*-0.5 to Mv*+3.0 mag. LBGs brighter than Mv* have larger rHL (0.40) than the fainter LBGs (0.23) on averag
e, and there is no bright LBGs with a small rHL. The LBGs brighter than Mv* 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 significant shift from those in the optical images. The images of all but one of the LBGs with K<21.5 mag are fitted well with Sersic profile with n index less than 2, similar to disk galaxies in the local universe. Assuming that the LBGs have a disk-shape, we compared their size-luminosity and size-stellar mass relation 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 the LBGs brighter than Mv*, the average surface stellar mass density is 3-6 times larger than those of the z=0 and z=1 disk galaxies. We also examine the profiles of the serendipitously observed DRGs. They are also fitted with the Sersic profiles with n<2. The implications of the dominance of n<2 population among galaxies at z~3 and the presence of the high surface stellar mass density disk systems are discussed.
