2016ApJ...820L..19P

We report the discovery of a rare compact early-type galaxy, SDSS J085431.18+173730.5 (hereafter cE_AGN). It has a half-light radius of R_e = 490 pc and a brightness of M_r = -18.08 mag. Optical spectroscopy available from the Sloan Digital Sky Survey (SDSS) reveals the presence of prominent broad-line emissions with the Hα broad component width of FWHM = 2400 km s^–1. The black hole (BH) mass, as estimated from the luminosity and width of the broad Hα emission, is 2.1 x 10⁶ M_☉. With the help of surface photometry, we perform a detailed analysis of the structural properties. The observed light distribution is best modeled with a double Sersic function. Fixing the outer component as an exponential disk, we find that the inner component has a Sersic index of n = 1.4. Considering the inner component as bulge/spheroidal we find that cE_AGN remains consistent in both the BH mass-bulge mass relation and the BH mass-bulge Sersic index relation. Given these observational properties, we discuss its possible origin investigating the surrounding environment where it is located.