BAT AGN Spectroscopic Survey - IV: Near-Infrared Coronal Lines, Hidden
  Broad Lines, and Correlation with Hard X-ray Emission
  We provide a comprehensive census of the near-Infrared (NIR, 0.8-2.4 $\mu$m)
spectroscopic properties of 102 nearby (z < 0.075) active galactic nuclei
(AGN), selected in the hard X-ray band (14-195 keV) from the Swift-Burst Alert
Telescope (BAT) survey. With the launch of the James Webb Space Telescope this
regime is of increasing importance for dusty and obscured AGN surveys. We
measure black hole masses in 68% (69/102) of the sample using broad emission
lines (34/102) and/or the velocity dispersion of the Ca II triplet or the CO
band-heads (46/102). We find that emission line diagnostics in the NIR are
ineffective at identifying bright, nearby AGN galaxies because ([Fe II]
1.257$\mu$m/Pa$\beta$ and H$_2$ 2.12$\mu$m/Br$\gamma$) identify only 25%
(25/102) as AGN with significant overlap with star forming galaxies and only
20% of Seyfert 2 have detected coronal lines (6/30). We measure the coronal
line emission in Seyfert 2 to be weaker than in Seyfert 1 of the same
bolometric luminosity suggesting obscuration by the nuclear torus. We find that
the correlation between the hard X-ray and the [Si VI] coronal line luminosity
is significantly better than with the [O III] luminosity. Finally, we find 3/29
galaxies (10%) that are optically classified as Seyfert 2 show broad emission
lines in the NIR. These AGN have the lowest levels of obscuration among the
Seyfert 2s in our sample ($\log N_{\rm H} < 22.43$ cm$^{-2}$), and all show
signs of galaxy-scale interactions or mergers suggesting that the optical broad
emission lines are obscured by host galaxy dust.
