Supermassive black hole masses in type II active galactic nuclei with polarimetric broad emission lines

Abstract

Aims. Type II active galactic nuclei (AGNs) with polarimetric broad emission lines provided strong evidence for the orientation-based unified model for AGNs. We want to investigate whether the polarimetric broad emission lines in type II AGNs can be used to calculate their central supermassive black hole (SMBH) masses, like that for type I AGNs. Methods. We collected 12 type II AGNs with polarimetric broad emission line widths from the literature, and calculated their central black hole masses from the polarimetric broad line widths and the isotropic [O III] luminosity. We also calculate the mass from stellar velocity dispersion, sigma(*), with the M(BH) - sigma(*) relation. Results. We find that: (1) the black hole masses derived from the polarimetric broad line width is on average larger than that from the MBH - sigma(*) relation by about 0.6 dex; (2) if these type II AGNs follow a MBH - sigma(*) relation, we find that the random velocity cannot be omitted and is comparable to the broad-line regions (BLRs) Keplerian velocity. It is consistent with the scenery of large outflow from the accretion disk suggested by Yong et al.