Infrared signature of active massive black holes in nearby dwarf galaxies

TL;DR

This study uses infrared data to identify active black holes in nearby dwarf galaxies, revealing smaller black holes than previously known and supporting the extension of the black hole-stellar mass relation to low-mass galaxies.

Contribution

It introduces a new infrared colour diagnostic method to detect active black holes in low-mass galaxies and estimates their masses, expanding understanding of black hole presence in dwarf galaxies.

Findings

Identified 303 candidate AGN in dwarf galaxies.

Black hole masses estimated to be 10^3 - 10^6 solar masses.

Black hole-stellar mass relation extends to low-mass galaxies.

Abstract

We investigate the possible presence of active galactic nuclei (AGN) in dwarf galaxies and other nearby galaxies to identify candidates for follow-up confirmation and dynamical mass measurements. We use the Wide-field Infrared Survey Explorer (WISE) All-Sky Release Source Catalog and examine the infrared colours of a sample of dwarf galaxies and other nearby galaxies in order to identify both unobscured and obscured candidate AGN by applying the infrared colour diagnostic. Stellar masses of galaxies are obtained using a combination of three independent methods. Black hole masses are estimated using the bolometric luminosity of the AGN candidates and computed for three cases of the bolometric-to-Eddington luminosity ratio. We identify 303 candidate AGN, of which 276 were subsequently found to have been independently identified as AGN via other methods. The remaining 9% require follow-up observations for confirmation. The activity is detected in galaxies with stellar masses from ~ 10^6 to 10^9 solar masses; assuming the candidates are AGN, the black hole masses are estimated to be ~ 10^3 - 10^6 solar masses, adopting L_bol = 0.1 L_Edd. The black hole masses probed are several orders of magnitude smaller than previously reported for centrally located massive black holes. We examine the stellar mass versus black hole mass relationship in this low galaxy mass regime. We find that it is consistent with the existing relation extending linearly (in log-log space) into the lower mass regime. These findings suggest that CMBH are present in low-mass galaxies and in the Local Universe, and provide new impetus for follow-up dynamical studies of quiescent black holes in local dwarf galaxies.