Infrared signature of active massive black holes in nearby dwarf galaxies

We have identified 313 nearby galaxies that display the infrared signature of black hole activity. Of these, eleven lie within a distance of 11 Mpc. Using the Wide-field Infrared Survey Explorer (WISE) All-Sky Release Source Catalog, we examine the IR colors of a sample of known nearby dwarf galaxies in order to identify both unobscured (type 1) and obscured (type 2) active galactic nuclei in these low-mass systems. We estimate the stellar and black hole masses for our nearby dwarf galaxy sample and find that activity is detected in galaxies with stellar masses from 10 to 10 M⊙ and that this activity is due to black holes with masses in the range 10 − 10 M⊙. The black hole masses probed here 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, and find that the existing relation extends to these lower masses. These findings indicate that central massive black holes are present in low-mass galaxies and in the Local Universe. These results provide new impetus for follow up dynamical studies of quiescent black holes in local dwarf galaxies.