Misc,

BASS XXV: DR2 Broad-line Based Black Hole Mass Estimates and Biases from Obscuration

, , , , , , , , , , , , , , , , , , , , , , , , , , , , and .
(2022)cite arxiv:2204.05321Comment: Accepted for publication in ApJS.

Abstract

We present measurements of broad emission lines and virial estimates of supermassive black hole masses ($M_BH$) for a large sample of ultra-hard X-ray selected active galactic nuclei (AGNs) as part of the second data release of the BAT AGN Spectroscopic Survey (BASS/DR2). Our catalog includes $M_BH$ estimates for a total 689 AGNs, determined from the H$\alpha$, H$\beta$, $MgIIłambda2798$, and/or $CIVłambda1549$ broad emission lines. The core sample includes a total of 512 AGNs drawn from the 70-month Swift/BAT all-sky catalog. We also provide measurements for 177 additional AGNs that are drawn from deeper Swift/BAT survey data. We study the links between $M_BH$ estimates and line-of-sight obscuration measured from X-ray spectral analysis. We find that broad H$\alpha$ emission lines in obscured AGNs ($(N_\rm H/cm^-2)> 22.0$) are on average a factor of $8.0_-2.4^+4.1$ weaker, relative to ultra-hard X-ray emission, and about $35_-12^~+7$\% narrower than in unobscured sources (i.e., $(N_H/cm^-2) < 21.5$). This indicates that the innermost part of the broad-line region is preferentially absorbed. Consequently, current single-epoch $M_BH$ prescriptions result in severely underestimated ($>$1 dex) masses for Type 1.9 sources (AGNs with broad H$\alpha$ but no broad H$\beta$) and/or sources with $(N_H/cm^-2) > 22.0$. We provide simple multiplicative corrections for the observed luminosity and width of the broad H$\alpha$ component ($LbH\alpha$ and FWHMbH$\alpha$) in such sources to account for this effect, and to (partially) remedy $M_BH$ estimates for Type 1.9 objects. As key ingredient of BASS/DR2, our work provides the community with the data needed to further study powerful AGNs in the low-redshift Universe.

Tags

Users

  • @gpkulkarni

Comments and Reviews