The supermassive black hole masses of reverberation-mapped active galactic nuclei

Abstract

Using different kinds of velocity tracers derived from the broad H$\beta$ profile (in the mean or rms spectrum) and the corresponding virial factors $f$, the central supermassive black hole (SMBH) masses ($M_{\rm BH}$) are calculated for a compiled sample of 120 reverberation-mapped (RM) AGNs. For its subsample of RM AGNs with measured stellar velocity dispersion ($\sigma_{\rm \ast}$), the multivariate linear regression technique is used to calibrate the mean value $f$, as well as the variable FWHM-based $f$. It is found that, whether excluding the pseudo-bulges or not, $M_{\rm BH}$ from the H$\beta$ line dispersion in the mean spectrum ($\sigma_{\rm H\beta,mean}$) has the smallest offset rms with respect to the $M_{\rm BH}-\sigma_{\ast}$ relation. For the total sample excluding SDSS-RM AGNs, with respect to $M_{\rm BH}$ from $\sigma_{\rm \ast}$ or that from the H$\beta$ line dispersion in the rms spectrum ($\sigma_{\rm H\beta,rms}$), it is found that we can obtain $M_{\rm BH}$ from the $\sigma_{\rm H\beta,mean}$ with the smallest offset rms of 0.38 dex or 0.23 dex, respectively. It implies that, with respect to the H$\beta$ FWHM, we prefer $\sigma_{\rm H\beta,mean}$ to calculate $M_{\rm BH}$ from the single-epoch spectrum. Using the FWHM-based $f$, we can improve $M_{\rm BH}$ calculation from FWHM(H$\beta$) and the mean $f$, with a decreased offset rms from 0.52 dex to 0.39 dex with respect to $M_{\rm BH}$ from $\sigma_{\rm \ast}$ for the subsample of 36 AGNs with $\sigma_{\rm \ast}$. The value of 0.39 dex is almost the same as that from $\sigma_{\rm H\beta,mean}$ and the mean $f$.