Single-Epoch Black Hole Mass Estimators For Broad-Line Active Galactic Nuclei: Recalibrating Hbeta with A New Approach

Understand

Based on an updated Hbeta reverberation mapping (RM) sample of 44 nearby active galactic nuclei (AGN), we propose a novel approach for black hole (BH) mass estimation using two filtered luminosities computed from single-epoch (SE) AGN spectra around the Hbeta region.

• We found that the two optimal-filter luminosities extract virial information (size and virial velocity of the broad line region, BLR) from the spectra, justifying their usage in this empirical BH mass estimator.
• The major advantages of this new recipe over traditional SE BH mass estimators utilizing continuum luminosity and broad line width are: 1) it has a smaller intrinsic scatter of 0.28 dex calibrated against RM masses; 2) it is extremely simple to use in practice, without any need to decompose the spectrum; 3) it produces unambiguous and highly repeatable results even with low signal-to-noise spectra.
• The combination of the two luminosities can also cancel out, to some extent, systematic luminosity errors potentially introduced by uncertainties in distance or flux calibration.