Luminosity Ratio between [O IV] 25.89 um Line and Nuclear Continuum 12 um as Diagnostic for “Buried” AGN. (arXiv:1904.01065v1 [astro-ph.HE])

Luminosity Ratio between [O IV] 25.89 um Line and Nuclear Continuum 12 um as Diagnostic for “Buried” AGN. (arXiv:1904.01065v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Yamada_S/0/1/0/all/0/1">Satoshi Yamada</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ueda_Y/0/1/0/all/0/1">Yoshihiro Ueda</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tanimoto_A/0/1/0/all/0/1">Atsushi Tanimoto</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kawamuro_T/0/1/0/all/0/1">Taiki Kawamuro</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Imanishi_M/0/1/0/all/0/1">Masatoshi Imanishi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Toba_Y/0/1/0/all/0/1">Yoshiki Toba</a>

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.

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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