Poster Presentation

Buried AGN Fraction in U/LIRGs Revealed by Luminosity Ratio between [O IV] 25.89 um line and Nuclear 12 um Continuum

Author(s): Satoshi Yamada (Kyoto Univ.) Yoshihiro Ueda (Kyoto Univ.) Atsushi Tanimoto (Kyoto Univ.) Taiki Kawamuro (NAOJ) Masatoshi Imanishi (NAOJ) Yoshiki Toba (Kyoto Univ.)

Presenter: Satoshi Yamada (Kyoto University)

We propose a new diagnostics that utilizes the [O IV] 25.89 um and nuclear (subarcsecond scale) 12 um luminosity ratio for identifying AGNs deeply ``buried'' in their tori. Utilizing a sample of 18 absorbed AGNs in the Swift/BAT catalog observed with Suzaku, we find that AGNs with small scattering fractions (< 0.5 %) tend to show weaker [O IV]-to-12 um luminosity ratios than the average of Seyfert 2 galaxies. This suggests that this ratio is a good indicator for identifying buried AGNs. Then, we apply this criterion to 23 local ultra/luminous infrared galaxies (U/LIRGs) in various merger stages hosting AGNs. We find that most of mid- to late-stage mergers have buried AGNs, while earlier stage ones (including non-mergers) do not. This result suggests that the fraction of buried AGNs in U/LIRGs increases as the galaxy-galaxy interaction becomes more significant.