Supermassive Black Hole Masses in Type II Active Galactic Nuclei with Polarimetric Broad Emission Lines

TL;DR

This study explores whether polarimetric broad emission lines in Type II AGNs can be used to estimate their supermassive black hole masses, comparing methods and analyzing the implications for AGN models.

Contribution

It demonstrates that black hole masses from polarimetric broad lines are systematically larger than those from stellar velocity dispersion, highlighting the role of outflows and orientation effects.

Findings

Masses from polarimetric lines are on average 0.6 dex larger than from $\sigma_*$.

The random velocity component is significant and comparable to BLR Keplerian velocity.

Supports the presence of large outflows from the accretion disk in Type II AGNs.

Abstract

Type II AGNs with polarimetric broad emission line provided strong evidence for the orientation-based unified model for AGNs. We want to investigate whether the polarimetric broad emission line in type II AGNs can be used to calculate their central supermassive black hole (SMBH) masses, like that for type I AGNs. We collected 12 type II AGNs with polarimetric broad emission line width from the literatures, and calculated their central black hole masses from the polarimetric broad line width and the isotropic \oiii luminosity. We also calculate the mass from stellar velocity dispersion, $\sigma_*$, with the $\mbh-\sigma_*$ relation.We find that: (1) the black hole masses derived from the polarimetric broad line width is averagely larger than that from the $\mbh- \sigma_*$ relation by about 0.6 dex, (2) If these type II AGNs follow $\mbh-\sigma_*$ relation, we find that the random velocity can't not be omitted and is comparable with the BLRs Keplerian velocity. It is consistent with the scenery of large outflow from the accretion disk suggested by Yong et al.