摘要
Revealing what fraction of galaxies harbor active galactic nuclei (AGNs) is central to understanding the black hole accretion history of the universe. However, optical and soft X-ray surveys miss the most highly obscured AGNs. Infrared (IR), instead, is more robust against absorption. Previous IR photometric surveys, however, only had four or five filters in mid-IR. Our AKARI North Ecliptic Pole wide field sample has 18 filters in mid-IR (nine from AKARI, four from WISE, and five from Spitzer), for the first time allowing a sophisticated mid-IR spectral energy distribution (SED) fitting diagnosis for a statistical number of sources (89178 over 5.4 deg <sup>2</sup> ). By using an SED fitting technique, we investigated the evolution of AGN fraction as a function of redshift and IR (8-1000μm) luminosity in an extinction-free way. We found that the AGN fraction (F <sub>AGN</sub> ) shows no sign of strong redshift evolution. Instead, F <sub>AGN</sub> increases with increasing IR luminosity in all redshift bins (0 < z < 2).