Extending Virial Black Hole Mass Estimates to Low-Luminosity or Obscured AGN: the cases of NGC 4395 and MCG -01-24-012

TL;DR

This paper develops new single epoch virial methods using broad line and X-ray luminosities to estimate black hole masses in low-luminosity and obscured AGN, extending previous techniques to previously inaccessible cases.

Contribution

It introduces calibrated SE relationships based on broad line and X-ray data, enabling BH mass estimates for obscured and low-luminosity AGN, validated with reverberation mapping.

Findings

Measured BH mass of NGC 4395 as 1.7 x 10^5 M_sol.

First BH mass estimate for MCG -01-24-012 as 1.5 x 10^7 M_sol.

Developed SE relations with 0.20 dex intrinsic spread.

Abstract

In the last decade, using single epoch (SE) virial based spectroscopic optical observations, it has been possible to measure the black hole (BH) mass on large type 1 Active Galactic Nuclei (AGN) samples. However this kind of measurements can not be applied on those obscured type 2 and/or low luminosity AGN where the nuclear component does not dominate in the optical. We have derived new SE relationships, based on the FWHM and luminosity of the broad line region component of the Pabeta emission line and/or the hard X-ray luminosity in the 14-195 keV band, which have the prospect of better working with low luminosity or obscured AGN. The SE relationships have been calibrated in the 10^5-10^9 M_sol mass range, using a sample of AGN whose BH masses have been previously measured using reverberation mapping techniques. Our tightest relationship between the reverberation-based BH mass and the SE virial product has an intrinsic spread of 0.20 dex. Thanks to these SE relations, in agreement with previous estimates, we have measured a BH mass of M_BH =1.7^+1.3_-0.7 X 10^5 M_sol for the low luminosity, type 1, AGN NGC 4395 (one of the smallest active galactic BH known). We also measured, for the first time, a BH mass of M_BH = 1.5^+1.1_-0.6 X 10^7 M_sol for the Seyfert 2 galaxy MCG -01-24-012.