The Subaru-XMM-Newton Deep Survey (SXDS). VIII. Multi-wavelength identification, optical/NIR spectroscopic properties, and photometric redshifts of X-ray sources†
Ouchi, Masami; Simpson, Chris; Curtis-Lake, Emma; Ueda, Yoshihiro; Yamada, Toru; Tamura, Naoyuki; Ohta, Kouji; Furusawa, Hisanori; Takata, Tadafumi; Silverman, John D.; Takato, Naruhisa; Hanami, Hitoshi; Morokuma, Tomoki; Akiyama, Masayuki; Yabe, Kiyoto; Sekiguchi, Kazuhiro; Croom, Scott; Fujishiro, Naofumi; Yoshikawa, Tomohiro; Iwamuro, Fumihide; Maihara, Toshinori; Kimura, Masahiko; Dalton, Gavin; Lewis, Ian; Lee, Hanshin; Macaulay, Edward; Watson, Mike G.; Moritani, Yuuki; Clarke, Frazer; Díaz Tello, Jorge
Japan, United Kingdom, Taiwan, United States, Australia, Argentina
Abstract
We report on 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 and mid-IR (MIR). We select a primary counterpart of each X-ray source by applying the likelihood ratio method to R-band, 3.6 μm, near-UV, and 24 μm source catalogs as well as matching catalogs of active galactic nucleus (AGN) candidates selected in 1.4 GHz radio and i '-band variability surveys. Once candidates for 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. Utilizing 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 by the nucleus. The scatter is compared with galaxies which have redshift and stellar mass distribution matched with the X-ray AGN. The UV-NIR (near-IR) 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.