Central Masses and Broad‐Line Region Sizes of Active Galactic Nuclei. II. A Homogeneous Analysis of a Large Reverberation‐Mapping Database

TLDR

Accurate line‑width measurement requires avoiding contaminating narrow components of emission lines. The study presents improved black‑hole masses for 35 AGNs from a consistent reanalysis of reverberation‑mapping data and introduces a more precise mass–luminosity relationship. The authors reanalyzed reverberation‑mapping data for 35 AGNs to compute black‑hole masses and calibrated the mass scale using the black‑hole mass–bulge velocity dispersion relation from a companion study. They find that using the CCF centroid and line dispersion measured in the variable spectrum yields the most precise virial products, with reverberation‑based black‑hole masses having ~30% random error, systematic uncertainties below a factor of three, and a real scatter in the mass–luminosity relation that may correlate with Eddington ratio or inclination.

Abstract

We present improved black hole masses for 35 active galactic nuclei (AGNs) based on a complete and consistent reanalysis of broad emission-line reverberation-mapping data. From objects with multiple line measurements, we find that the highest precision measure of the virial product cτΔV2/G, where τ is the emission-line lag relative to continuum variations and ΔV is the emission-line width, is obtained by using the cross-correlation function centroid (as opposed to the cross-correlation function peak) for the time delay and the line dispersion (as opposed to FWHM) for the line width and by measuring the line width in the variable part of the spectrum. Accurate line-width measurement depends critically on avoiding contaminating features, in particular the narrow components of the emission lines. We find that the precision (or random component of the error) of reverberation-based black hole mass measurements is typically around 30%, comparable to the precision attained in measurement of black hole masses in quiescent galaxies by gas or stellar dynamical methods. Based on results presented in a companion paper by Onken et al., we provide a zero-point calibration for the reverberation-based black hole mass scale by using the relationship between black hole mass and host-galaxy bulge velocity dispersion. The scatter around this relationship implies that the typical systematic uncertainties in reverberation-based black hole masses are smaller than a factor of 3. We present a preliminary version of a mass-luminosity relationship that is much better defined than any previous attempt. Scatter about the mass-luminosity relationship for these AGNs appears to be real and could be correlated with either Eddington ratio or object inclination.