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arXiv · 1904.01065

Luminosity Ratio between [O IV] 25.89 um Line and Nuclear Continuum 12 um as Diagnostic for "Buried" AGN

Satoshi Yamada·Yoshihiro Ueda·Atsushi Tanimoto·Taiki Kawamuro·Masatoshi Imanishi·Yoshiki Toba
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Abstract

We propose new diagnostics that utilize the [O IV] 25.89 $\mu$m and nuclear (subarcsecond scale) 12 $\mu$m luminosity ratio for identifying whether an AGN is deeply `buried' in their surrounding material. Utilizing a sample of 16 absorbed AGNs at redshifts lower than 0.03 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 $\mu$m 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 AGNs in most of mid- to late-stage mergers are buried, while those in earlier stage ones (including non-merger) are not. This result suggests that the fraction of buried AGNs in U/LIRGs increases as the galaxy-galaxy interaction becomes more significant.

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Satoshi Yamada, Yoshihiro Ueda, Atsushi Tanimoto, Taiki Kawamuro, Masatoshi Imanishi, Yoshiki Toba. 2019-04-01. Luminosity Ratio between [O IV] 25.89 um Line and Nuclear Continuum 12 um as Diagnostic for "Buried" AGN. https://doi.org/10.3847/1538-4357/ab14f0

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