Kavli Affiliate: Claudio Ricci
| First 5 Authors: Michael J. Koss, Benny Trakhtenbrot, Claudio Ricci, Kyuseok Oh, Franz E. Bauer
| Summary:
We present new central stellar velocity dispersions for 484 Sy 1.9 and Sy 2
from the second data release of the Swift/BAT AGN Spectroscopic Survey (BASS
DR2). This constitutes the largest study of velocity dispersion measurements in
X-ray selected, obscured AGN with 956 independent measurements of the Ca H+K
and Mg b region (3880-5550A) and the Ca triplet region (8350-8730A) from 642
spectra mainly from VLT/Xshooter or Palomar/DoubleSpec. Our sample spans
velocity dispersions of 40-360 km/s, corresponding to 4-5 orders of magnitude
in black holes mass (MBH=10^5.5-9.6 Msun), bolometric luminosity
(LBol~10^{42-46 ergs/s), and Eddington ratio (L/Ledd~10^{-5}-2). For 281 AGN,
our data provide the first published central velocity dispersions, including 6
AGN with low mass black holes (MBH=10^5.5-6.5 Msun), discovered thanks to our
high spectral resolution observations (sigma~25 km/s). The survey represents a
significant advance with a nearly complete census of hard-X-ray selected
obscured AGN with measurements for 99% of nearby AGN (z<0.1) outside the
Galactic plane. The BASS AGN have higher velocity dispersions than the more
numerous optically selected narrow line AGN (i.e., ~150 vs. ~100 km/s), but are
not biased towards the highest velocity dispersions of massive ellipticals
(i.e., >250 km/s). Despite sufficient spectral resolution to resolve the
velocity dispersions associated with the bulges of small black holes (~10^4-5
Msun), we do not find a significant population of super-Eddington AGN. Using
estimates of the black hole sphere of influence, direct stellar and gas black
hole mass measurements could be obtained with existing facilities for more than
~100 BASS AGN.
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