Active Galactic Nuclei with Double-Peaked Balmer Lines: I. Black Hole Masses and the Eddington ratios

TL;DR

This study analyzes double-peaked broad-line AGNs from SDSS to estimate black hole masses, Eddington ratios, and BLR geometry, revealing deviations from virial assumptions and correlations with peak separation.

Contribution

It provides new black hole mass and Eddington ratio estimates for 52 double-peaked AGNs using stellar velocity dispersions and emission line modeling.

Findings

Black hole masses range from 10^7 to 5.5×10^8 solar masses.

The BLR geometry factor f deviates from 0.75, indicating non-virial dynamics.

Peak separation correlates with Eddington ratio and SMBH mass.

Abstract

Using the stellar population synthesis, we model the stellar contribution for a sample of 110 double-peaked broad-lines AGNs from the Sloan Digital Sky Survey (SDSS). The stellar velocity dispersions ($\sigma_*$) are obtained for 52 double-peaked AGNs with obvious stellar absorption features, ranging from 106 to 284 \kms. We also use multi-component profiles to fit \OIII $\lambda\lambda4959,5007$ and H$\beta$ emission lines. Using the well-established $M_{\rm bh}-\sigma_*$ relation, the black hole masses are calculated to range from $1.0\times 10^{7}$ to $5.5\times 10^{8}$ $\Msun$, and the Eddington ratio from about 0.01 to about 1. Comparing with the known $R_{\rm BLR}-L$ relation, we can get the factor $f$, which indicates BLRs' geometry, inclination and kinematics. We find that $f$ far deviates from 0.75, suggesting the non-virial dynamics of broad line regions. The peak separation is mildly correlated with the Eddington ratio and SMBH mass with almost the same correlation coefficients. It implies that it is difficult to detect obvious double-peak AGNs with higher Eddington ratios. Using the monochromatic luminosity at 5100\AA to trace the bolometric luminosity, we find that the external illumination of the accretion disk is needed to produce the observed strength of H$\alpha$ emission line.