Black Hole Masses of Active Galaxies with Double‐peaked Balmer Emission Lines

Abstract

We have obtained near-IR spectra of five AGNs that exhibit double-peaked Balmer emission lines (NGC 1097, Pictor A, PKS 0921-213, 1E 0450.30-1817, and IRAS 0236.6-3101). The stellar velocity dispersions of the host galaxies were measured from the Ca II λλ8494, 8542, 8662 absorption lines and were found to range from 140 to 200 km s-1. Using the well-known correlation between the black hole mass and the stellar velocity dispersion, the black hole masses in these galaxies were estimated to range from 4 × 107 to 1.2 × 108 M☉. We supplement the observations presented here with estimates of the black holes masses for five additional double-peaked emitters (Arp 102B, 3C 390.3, NGC 4579, NGC 4203, and M81) obtained by other authors using similar methods. Using these black hole masses, we infer the ratio of the bolometric luminosity to the Eddington luminosity, (Lbol/LEdd). We find that two objects (Pictor A and PKS 0921-213) have Lbol/LEdd ~ 0.2, whereas the other objects have Lbol/LEdd 10-2 (nearby, low-luminosity double-peaked emitters are the most extreme, with Lbol/LEdd 10-4). The physical timescales in the outer regions of the accretion disks (at r ~ 103GM/c2) in these objects were also estimated and range from a few months for the dynamical timescale to several decades for the sound crossing timescale. The profile variability in these objects is typically an order of magnitude longer than the dynamical time, but we note that variability occurring on the dynamical timescale has not been ruled out by the observations.