The Binary Nucleus in VCC 128: A Candidate Supermassive Black Hole in a Dwarf Elliptical Galaxy
Pasquali, Anna; Seth, Anil; Debattista, Victor P.; Ferreras, Ignacio; Morelli, Lorenzo; De Rijcke, Sven
United States, Canada, United Kingdom, Germany, Belgium, Chile
Abstract
Hubble Space Telescope (HST) Wide Field Planetary Camera 2 (WFPC2) images of the Virgo Cluster dwarf elliptical galaxy VCC 128 reveal an apparently double nucleus. The two components, which are separated by ~32 pc in projection, have the same magnitude and color. We present a spectrum of this double nucleus and show that it is inconsistent with one or both components being emission-line background objects or foreground stars. The most likely interpretation is that, as suggested by Lauer et al. for the double nucleus in NGC 4486B, we are seeing a nuclear disk surrounding a supermassive black hole. This is only the second time an early-type dwarf (dE/dSph) galaxy has been suggested to host a supermassive black hole.