# 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

## TL;DR

This study uses extensive 18-band mid-infrared SED fitting to determine the AGN fraction in galaxies, revealing it depends on luminosity but not strongly on redshift, thus improving understanding of black hole growth.

## Contribution

First to utilize 18-band mid-IR data for robust, extinction-free AGN fraction analysis across redshift and luminosity in a large galaxy sample.

## Key findings

- AGN fraction increases with IR luminosity across all redshifts.
- No significant redshift evolution of AGN fraction observed.
- Mid-IR SED fitting effectively identifies obscured AGNs.

## 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 $\mu$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 ($0<z<2$).