High-ionization mid-infrared lines as black hole mass and bolometric luminosity indicators in active galactic nuclei

TL;DR

This study establishes that high-ionization mid-infrared emission lines can serve as reliable indicators of black hole mass and luminosity in active galactic nuclei, especially useful for obscured systems.

Contribution

It introduces new correlations between MIR line properties and black hole characteristics, enabling estimates in obscured AGN where optical methods are ineffective.

Findings

MIR line velocity dispersions correlate with black hole mass.

Line luminosities relate to optical continuum and black hole mass.

Lines are often resolved, indicating their origin from the narrow-line region.

Abstract

We present relations of the black hole mass and the optical luminosity with the velocity dispersion and the luminosity of the [Ne V] and the [O IV] high-ionization lines in the mid-infrared (MIR) for 28 reverberation-mapped active galactic nuclei. We used high-resolution Spitzer Infrared Spectrograph and Infrared Space Observatory Short Wavelength Spectrometer data to fit the profiles of these MIR emission lines that originate from the narrow-line region of the nucleus. We find that the lines are often resolved and that the velocity dispersion of [Ne V] and [O IV] follows a relation similar to that between the black hole mass and the bulge stellar velocity dispersion found for local galaxies. The luminosity of the [Ne V] and the [O IV] lines in these sources is correlated with that of the optical 5100A continuum and with the black hole mass. Our results provide a means to derive black hole properties in various types of active galactic nuclei, including highly obscured systems.