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 \approx 8.5 \mathrm { ~ { } 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 _ { \mathrm { b } } \sim 3 \times 10 ^ { 10 } \mathrm { ~ { } K } at observing frequency \nu = 7.6 \mathrm { ~ { } GHz } ) and too luminous ( 1.4 GHz luminosity L _ { \mathrm { 1.4 GHz } } \sim 10 ^ { 25 } \mathrm { ~ { } W~ { } Hz } ^ { -1 } ) to be powered by anything but a SMBH , but its host galaxy is much smaller ( \sim 0.9 \mathrm { ~ { } kpc } \times 0.6 \mathrm { ~ { } kpc } full width between half-maximum points ) and optically fainter ( R-band absolute magnitude M _ { \mathrm { r } } \approx - 18.2 ) than any other radio galaxy .
Its high radial velocity v _ { \mathrm { r } } \approx 1860 \mathrm { ~ { } 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 supermassive black hole fleeing from the BCG with space velocity v \gtrsim 2000 \mathrm { ~ { } km~ { } s } ^ { -1 } .
The radio galaxy has mass M \lesssim 6 \times 10 ^ { 9 } M _ { \odot } and infrared luminosity L _ { \mathrm { IR } } \sim 3 \times 10 ^ { 11 } L _ { \odot } close to its dust Eddington limit , so it is vulnerable to further mass loss from radiative feedback .