Estimating Masses of Supermassive Black Holes in Active Galactic Nuclei from the Halpha Emission Line

TL;DR

This paper develops a new method to estimate supermassive black hole masses in active galactic nuclei using only the Halpha emission line's luminosity and width, improving accuracy and simplicity.

Contribution

It introduces a novel mass estimator based solely on Halpha line properties, utilizing remeasured reverberation mapping data for enhanced precision.

Findings

Mass estimates have a typical accuracy of 0.2-0.3 dex.

The estimator requires only a single spectrum of the Halpha line.

Inclusion of luminosity, line width, and Eddington ratio improves mass accuracy.

Abstract

The goal of this project is to construct an estimator for the masses of supermassive black holes in active galactic nuclei (AGNs) based on the broad Halpha emission line. We make use of published reverberation mapping data. We remeasure all Halpha time lags from the original data as we find that often the reverberation measurements are improved by detrending the light curves. We produce mass estimators that require only the Halpha luminosity and the width of the Halpha emission line as characterized by either the FWHM or the line dispersion. It is possible, on the basis of a single spectrum covering the Halpha emission line, to estimate the mass of the central supermassive black hole in AGNs, taking into account all three parameters believed to affect mass measurement: luminosity, line width, and Eddington ratio. The typical formal accuracy in such estimates is of order 0.2-0.3 dex.