ANTICORRELATION BETWEEN THE MASS OF A SUPERMASSIVE BLACK HOLE AND THE MASS ACCRETION RATE IN TYPE 1 ULTRALUMINOUS INFRARED GALAXIES AND NEARBY QSOs

摘要

We discovered a significant anticorrelation between the mass of a supermassive black hole (SMBH), M_(BH), and the luminosity ratio of infrared to active galactic nuclei (AGN) Eddington luminosity, L_(IR)/L_(Edd), over 4 orders of magnitude for ultraluminous infrared galaxies with type 1 Seyfert nuclei (type 1 ULIRGs) and nearby QSOs. This anticorrelation (M_(BH) vs. L_(IR)/L_(Edd)) can be interpreted as the anticorrelation between the mass of a SMBH and the rate of mass accretion onto a SMBH normalized by the AGN Eddington rate, M_(BH)/M_(Edd). In other words, the mass accretion rate M_(BH) is not proportional to that of the central BH mass. Thus, this anticorrelation indicates that BH growth is determined by the external mass supply process, and not the AGN Eddington-limited mechanism. Moreover, we found an interesting tendency for type 1 ULIRGs to favor a super-Eddington accretion flow, whereas QSOs tended to show a sub-Eddington flow. On the basis of our findings, we suggest that a central SMBH grows by changing its mass accretion rate from super-Eddington to sub-Eddington. According to a coevolution scenario of ULIRGs and QSOs based on the radiation drag process, it has been predicted that a self-gravitating massive torus, whose mass is larger than a central BH, exists in the early phase of BH growth (type 1 ULIRG phase) but not in the final phase of BH growth (QSO phase). At the same time, if one considers the mass accretion rate onto a central SMBH via a turbulent viscosity, the anticorrelation (M_(BH) vs. L_(IR)/L_(Edd)) is well explained by the positive correlation between the mass accretion rate M_(BH) and the mass ratio of a massive torus to a SMBH.