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arXiv · 1902.02800

Does AGN Fraction Depend on Redshift or Luminosity? An Extinction-Free Test by 18-band Mid-infrared SED Fitting in the AKARI NEP Wide Field

Chia-Ying Chiang·Tomotsugu Goto·Tetsuya Hashimoto·Seong-Jin Kim·Hideo Matsuhara·Nagisa Oi
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Abstract

Revealing what fraction of galaxies harbor AGN is central in understanding 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 4 or 5 filters in mid-IR. Our AKARI North Ecliptic Pole (NEP) wide field sample has 18 filters in mid-IR (9 from AKARI, 4 from WISE, and 5 from Spitzer), for the first time, allowing a sophisticated mid-IR SED fitting diagnosis for a statistical number of sources (89178 over 5.4 deg$^2$). By using a SED fitting technique, we investigate the evolution of AGN fraction as a function of redshift and IR (8-1000 $μ$m) luminosity in an extinction-free way. We found that the AGN fraction (F$_{\rm AGN}$) shows no sign of strong redshift evolution. Instead, F$_{\rm AGN}$ increases with increasing IR luminosity in all redshifts bins ($0<z<2$).

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Chia-Ying Chiang, Tomotsugu Goto, Tetsuya Hashimoto, Seong-Jin Kim, Hideo Matsuhara, Nagisa Oi. 2019-02-07. Does AGN Fraction Depend on Redshift or Luminosity? An Extinction-Free Test by 18-band Mid-infrared SED Fitting in the AKARI NEP Wide Field. https://doi.org/10.1093/pasj%2Fpsz012

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