Chia-Ying Chiang (NTHU); Tomotsugu Goto (NTHU)
It has been of great challenge to distinguish star-forming galaxies and active galactic nuclei (AGNs). Both optical-selected and most X-ray-selected AGN samples suffer from extinction, while mid-IR bands are nearly free of extinction and ideal for AGN selection. However, the lack of continuous mid-IR data in previous surveys made AGN selection difficult until the launch of AKARI. We use an AKARI NEP wide field sample, which contains the most sources (around 900000) to date for the Spectral Energy Distribution (SED) fitting method. The sample contains the continuous 9 mid-IR bands of AKARI, 4 bands of WISE and 5 bands of SPITZER and is the first statistical mid-IR sample for AGN selection. With the SED fitting result, we investigate the evolution of AGN fraction as a function of redshift and IR luminosity in an extinction-free way. The results cast important impact on IR luminosity function and the evolution of galaxies in cosmic time.