Kavli Affiliate: Claudio Ricci
| First 5 Authors: Kyuseok Oh, Michael J. Koss, Yoshihiro Ueda, Daniel Stern, Claudio Ricci
| Summary:
We present the second catalog and data release of optical spectral line
measurements and AGN demographics of the BAT AGN Spectroscopic Survey, which
focuses on the of Swift-BAT hard X-ray detected AGNs. We use spectra from
dedicated campaigns and publicly available archives to investigate spectral
properties of most of the AGNs listed in the 70-month Swift-BAT all-sky
catalog; specifically, 743 of the 746 unbeamed and unlensed AGNs (99.6%). We
find a good correspondence between the optical emission line widths and the
hydrogen column density distributions using the X-ray spectra, with a clear
dichotomy of AGN types for NH = 10^22 cm-2. Based on optical emission-line
diagnostics, we show that 48%-75% of BAT AGNs are classified as Seyfert,
depending on the choice of emission lines used in the diagnostics. The fraction
of objects with upper limits on line emission varies from 6% to 20%. Roughly 4%
of the BAT AGNs have lines too weak to be placed on the most commonly used
diagnostic diagram, [O III]{lambda}5007/Hb{eta} versus [N
II]{lambda}6584/H{alpha}, despite the high signal-to-noise ratio (S/N) of
their spectra. This value increases to 35% in the [O III]{lambda}5007/[O
II]{lambda}3727 diagram, owing to difficulties in line detection. Compared to
optically-selected narrow-line AGNs in the Sloan Digital Sky Survey, the BAT
narrow-line AGNs have a higher rate of reddening/extinction, with
H{alpha}/Hb{eta} > 5 (~ 36%), indicating that hard X-ray selection more
effectively detects obscured AGNs from the underlying AGN population. Finally,
we present a subpopulation of AGNs that feature complex broad-lines (34%,
250/743) or double-peaked narrow emission lines (2%, 17/743).
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