Active Galactic Nuclei with Double‐Peaked Balmer Lines. I. Black Hole Masses and Eddington Ratios

Abstract

Using stellar population synthesis, we model the stellar contribution for a sample of 110 double-peaked broad-line active galactic nuclei (AGNs) from the Sloan Digital Sky Survey (SDSS). The stellar velocity dispersions (σ*) are obtained for 52 double-peaked AGNs with obvious stellar absorption features, ranging from 106 to 284 km s-1. We also use multicomponent profiles to fit O III λλ4959, 5007 and Hβ emission lines. Using the well-established Mbh-σ* relation, the black hole masses are calculated to range from 1.0 × 107 to 5.5 × 108 M☉, and the Eddington ratio from ~0.01 to ~1. Comparing these with the known RBLR-L relation, we can find the factor f, which indicates the BLRs' geometry, inclination, and kinematics. We find that f deviates greatly from 0.75, suggesting the nonvirial dynamics of broad-line regions. The peak separation is mildly correlated with the Eddington ratio and SMBH mass with almost the same correlation coefficients. This implies that it will be difficult to detect obvious double-peaked AGNs with higher Eddington ratios. Using the monochromatic luminosity at 5100 Å to trace the bolometric luminosity, we find that external illumination of the accretion disk is needed to produce the observed strength of the Hα emission line.