A Nearly Naked Supermassive Black Hole

Abstract

During a systematic search for supermassive black holes (SMBHs) not in galactic nuclei, we identified the compact, symmetric radio source B3 1715+425 with an emission-line galaxy offset ≈ 8.5 {kpc} from the nucleus of the brightest cluster galaxy (BCG) in the redshift z = 0.1754 cluster ZwCl 8193. B3 1715+425 is too bright (brightness temperature {T}_{{b}}∼ 3× {10}¹⁰ {{K}} at observing frequency ν =7.6 {GHz}) and too luminous (1.4 GHz luminosity {L}_1.4{GHz}∼ {10}²⁵ {{W}} {{Hz}}^-1) to be powered by anything but an SMBH, but its host galaxy is much smaller (∼ 0.9 {kpc}× 0.6 {kpc} full width between half-maximum points) and optically fainter (R-band absolute magnitude {M}_{{r}}≈ -18.2) than any other radio galaxy. Its high radial velocity {v}_{{r}}≈ 1860 {km} {{{s}}}^-1 relative to the BCG, continuous ionized wake extending back to the BCG nucleus, and surrounding debris indicate that the radio galaxy was tidally shredded passing through the BCG core, leaving a nearly naked SMBH fleeing from the BCG with space velocity v≳ 2000 {km} {{{s}}}^-1. The radio galaxy has mass M≲ 6× {10}⁹ {M}_⊙ and infrared luminosity {L}_{IR}∼ 3× {10}¹¹ {L}_⊙ close to its dust Eddington limit, so it is vulnerable to further mass loss from radiative feedback.