AGN have Underweight Black Holes and Reach Eddington

Abstract

Eddington outflows probably regulate the growth of supermassive black holes (SMBH) in AGN. I show that effect of the Rayleigh--Taylor instability on these outflows means that SMBH masses are likely to be a factor of a few below the $M - \sigma$ relation in AGN. This agrees with the suggestion by Batcheldor (2010) that the $M - \sigma$ relation defines an upper limit to the black hole mass. I further argue that observed AGN black holes must spend much of their lives accreting at the Eddington rate. This is already suggested by the low observed AGN fraction amongst all galaxies despite the need to grow to the masses required by the Soltan relation, and is reinforced by the suggested low SMBH masses. Most importantly, this is the simplest explanation of the recent discovery by Tombesi et al (2010a, b) of the widespread incidence of massive ultrafast X--ray outflows in a large sample of AGN.