Title: An extinction free AGN selection by 18-band SED fitting in mid-infrared in the AKARI NEP deep field,
Abstract: We have developed an efficient Active Galactic Nucleus (AGN) selection method
using 18-band Spectral Energy Distribution (SED) fitting in mid-infrared
(mid-IR). AGNs are often obscured by gas and dust, and those obscured AGNs tend
to be missed in optical, UV and soft X-ray observations. Mid-IR light can help
us to recover them in an obscuration free way using their thermal emission. On
the other hand, Star-Forming Galaxies (SFG) also have strong PAH emission
features in mid-IR. Hence, establishing an accurate method to separate
populations of AGN and SFG is important. However, in previous mid-IR surveys,
only 3 or 4 filters were available, and thus the selection was limited. We
combined AKARI's continuous 9 mid-IR bands with WISE and Spitzer data to create
18 mid-IR bands for AGN selection. Among 4682 galaxies in the AKARI NEP deep
field, 1388 are selected to be AGN hosts, which implies an AGN fraction of
29.6$\pm$0.8$\%$ (among them 47$\%$ are Seyfert 1.8 and 2). Comparing the
result from SED fitting into WISE and Spitzer colour-colour diagram reveals
that Seyferts are often missed by previous studies. Our result has been tested
by stacking median magnitude for each sample. Using X-ray data from Chandra, we
compared the result of our SED fitting with WISE's colour box selection. We
recovered more X-ray detected AGN than previous methods by 20$\%$.