We investigate the calibration and application of reverberation mapping techniques for determining black hole (BH)masses in active galactic nuclei (AGNs). We present revised BH mass determinations for several AGNs based on the use of updated methodologies with archival data, demonstrating significant reductions in the sizes of the BH mass uncertainties. Moreover, the study of the Seyfert 1 galaxy, NGC 3783, shows that the gas in the broad-line region of this AGN obeys the virial theorem.
We use measurements of stellar velocity dispersions, σ*, in AGNs and the assumption that AGNs follow the same relation between BH mass and σ* as quiescent galaxies to provide the first empirical calibration for reverberation-based BH masses. We also attempt to determine an independent calibration of these masses by studying the reverberation-mapped AGN, NGC 4151, with ground- and space-based observations, and by trying to constrain the BH mass through modeling of the galaxy’s stellar dynamics.
We estimate the BH masses and bolometric luminosities in ~400 AGNs selected from the multi-wavelength AGN and Galaxy Evolution Survey (AGES), where the BH masses are calculated from scaling relationships that have grown out of reverberation mapping. We find the distribution of Eddington ratios at fixed luminosity to be sharply peaked around value of 1/3, with a dispersion of just 0.3 dex. The distribution of Eddington ratios at fixed mass looks to be similarly narrow, and we are able to confirm a drop in the underlying distribution at low Eddington ratios for certain combinations of redshift and BH mass – all previous studies in these redshift-mass bins are affected by selection effects at low Eddington ratio (as are the AGES data in lower mass or higher redshift bins). The dominance of AGN accretion at rates relatively close to the Eddington limit has important implications for the growth of BHs and the joint evolution of BHs and their host galaxies.