Stellar disruption by supermassive black holes and the quasar radio loudness dichotomy

Abstract

The origin of the dichotomy of radio loudness among quasars can be explained using recent findings that the mass of the central supermassive black hole (SMBH) in extended radio-loud quasars is systematically a few times that of their counterparts in radio-quiet quasars. This sensitive dependence of radio jet ejection on SMBH mass probably arises from the blockage of jets by the presence of substantial quantities of gas tidally stripped from stars by the central BH. This disruptive gas, however, will only be available around BHs with masses less than M_c≳10⁸ M_⊙, for which the tidal disruption radius lies outside the SMBH's event horizon. Consequently, we find that AGNs with M_BH > M_c can successfully launch jets with a wide range of powers, thus producing radio-loud quasars. The great majority of jets launched by less massive BHs, however, will be truncated in the vicinity of the SMBH due to mass loading from this stellar debris. This scenario also can naturally explain the remarkable dearth of extended radio structures in quasars showing broad absorption line spectra.