Speaker
Description
We present two independent measurements of stellar velocity dispersions ( $\sigma_\mathrm{\star}$ ) from the Ca H K & Mg I region (388--555 nm) and the Calcium Triplet region (CaT, 835--875 nm) for 173 hard X-ray selected Type 1 AGNs from 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 ($M_\mathrm{BH}$) estimates and $\sigma_\mathrm{\star}$ measurements obtained from high-resolution data, allowing test various aspects of the usage of such methods for supermassive black hole studies. We report that two independent $\sigma_\mathrm{\star}$ measurements are highly consistent with each other, with an average offset of merely $0.002\pm0.001$ dex. Comparing $M_\mathrm{BH}$ estimates based on broad emission lines and on stellar absorption features (coupled with the $M_\mathrm{BH}$ - $\sigma_\mathrm{\star}$ relation), we find that the former is systematically lower, by $\approx$ 0.12 dex on average than the latter. Consequently, Eddington ratios estimated through these $M_\mathrm{BH}$ 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 $M_\mathrm{BH}$ - $\sigma_\mathrm{\star}$ relation and the Eddington ratio. Our sample of Type 1 AGNs shows a shallower $M_\mathrm{BH}$ - $\sigma_\mathrm{\star}$ relation (a power law exponent of $\approx$ 3.5) compared with that of inactive galaxies, confirming earlier results obtained from smaller samples.
