Tracing the co-evolution path of super massive black holes and spheroids with AKARI-selected ultra-luminous IR galaxies at intermediate redshifts
We present the stellar population and ionized-gas outflow properties of ultra-luminous IR galaxies (ULIRGs) at z=0.1-1.0, which are selected from the AKARI FIR all-sky survey. We construct a catalog of 1077 ULIRGs to examine feedback effect after major mergers. 202 out of the 1077 ULIRGs are spectroscopically identified by SDSS and Subaru/FOCAS observations. Thanks to deeper depth and higher resolution of AKARI compared to the previous IRAS survey, and reliable identification from WISE MIR pointing, the sample is unique in identifying optically-faint (i~20) IR-bright galaxies, which could be missed in previous surveys. A self-consistent spectrum-SED decomposition method, which constrains stellar population properties in SED modeling based on spectral fitting results, has been employed for 149 ULIRGs whose optical continua are dominated by host galaxies. They are massive galaxies (Mstar~1E11-1E12 Msun), associated with intense star formation activities (SFR~200-2000 Msun/yr). The sample cover a range of AGN bolometric luminosity of 1E10-1E13 Lsun, and the outflow velocity measured from [OIII] line shows an association with AGN luminosity. Eight galaxies show extremely fast outflows with velocity up to 1500-2000 km/s. However, the co-existence of vigorous starbursts and strong outflows suggests the star formation has not been quenched during ULIRG phase. By deriving stellar mass and mass fraction of young stellar population, we find no significant discrepancies between stellar properties of ULIRGs with weak and powerful AGNs. The results are not consistent with the merger-induced evolutionary scenario, which suggests that SF-dominated ULIRGs show smaller stellar mass and younger stellar populations compared to AGN-dominated ULIRGs.