Kavli Affiliate: Claudio Ricci
| First 5 Authors: Turgay Caglar, Michael J. Koss, Leonard Burtscher, Benny Trakhtenbrot, M. Kiyami Erdim
| Summary:
We present two independent measurements of stellar velocity dispersions (
$sigma_rm{star}$ ) from the Ca,H+K & Mg,textsc{i} region
(3880–5550~AA) and the Calcium Triplet region (CaT, 8350–8750~AA) for 173
hard X-ray-selected Type 1 AGNs ($z leq$ 0.08) from the 105-month Swift-BAT
catalog. We construct one of the largest samples of local Type 1 AGNs that have
both single-epoch (SE) ‘virial’ black hole mass ($M_rm{BH}$) estimates and
$sigma_rm{star}$ measurements obtained from high spectral resolution data,
allowing us to test the usage of such methods for SMBH studies. We find that
the two independent $sigma_rm{star}$ measurements are highly consistent with
each other, with an average offset of only $0.002pm0.001$ dex. Comparing
$M_rm{BH}$ estimates based on broad emission lines and stellar velocity
dispersion measurements, we find that the former is systematically lower by
$approx$0.12 dex. Consequently, Eddington ratios estimated through broad-line
$M_rm{BH}$ determinations are similarly biased (but in the opposite way). We
argue that the discrepancy is driven by extinction in the broad-line region
(BLR). We also find an anti-correlation between the offset from the $M_rm{BH}$
– $sigma_rm{star}$ relation and the Eddington ratio. Our sample of Type 1
AGNs shows a shallower $M_rm{BH}$ – $sigma_rm{star}$ relation (with a power
law exponent of $approx$3.5) compared with that of inactive galaxies (with a
power-law exponent of $approx$4.5), confirming earlier results obtained from
smaller samples.
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