Infrared signature of active massive black holes in nearby dwarf
  galaxies
  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.
