Pox 52: a Dwarf Seyfert 1 Galaxy with an Intermediate-mass Black Hole

We describe new optical images and spectra of POX 52, a dwarf galaxy with an active nucleus that was originally detected in the POX objective-prism survey. While POX 52 was originally thought to be a Seyfert 2 galaxy, the new data reveal an emission-line spectrum very similar to that of the dwarf Seyfert 1 galaxy NGC 4395, with broad components to the permitted line profiles, and we classify POX 52 as a Seyfert 1 galaxy. The host galaxy appears to be a dwarf elliptical, and its brightness profile is best fit by a Sérsic model with an index of 3.6±0.2 and a total magnitude of MV = −17.6. Applying mass-luminosity-linewidth scaling relations to estimate the black hole mass from the broad Hβ linewidth and nonstellar continuum luminosity, we find MBH ≈ 1.6×105 M⊙. The stellar velocity dispersion in the host galaxy, measured from the Ca II λ8498,8542 Å lines, is 36± 5 km s−1, also suggestive of a black hole mass of order 105 M⊙. Further searches for active nuclei in dwarf galaxies can provide unique constraints on the demographics of black holes in the mass range below 106 M⊙. Subject headings: galaxies: active — galaxies: dwarf — galaxies: individual (POX 52) — galaxies: kinematics and dynamics — galaxies: nuclei — galaxies: Seyfert