The Subaru-XMM-Newton Deep Survey (SXDS) VIII.: Multi-wavelength
  Identification, Optical/NIR Spectroscopic Properties, and Photometric
  Redshifts of X-ray Sources
  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.
