Astrophys. J., 799, 98 (2015/January-3)
X-ray constraints on the local supermassive black hole occupation fraction.
MILLER B.P., GALLO E., GREENE J.E., KELLY B.C., TREU T., WOO J.-H. and BALDASSARE V.
Abstract (from CDS):
Distinct seed formation mechanisms are imprinted upon the fraction of dwarf galaxies currently containing a central supermassive black hole. Seeding by Population III remnants is expected to produce a higher occupation fraction than is generated with direct gas collapse precursors. Chandra observations of nearby early-type galaxies can directly detect even low-level supermassive black hole activity, and the active fraction immediately provides a firm lower limit to the occupation fraction. Here, we use the volume-limited AMUSE surveys of ∼200 optically selected early-type galaxies to characterize simultaneously, for the first time, the occupation fraction and the scaling of LX with Mstar, accounting for intrinsic scatter, measurement uncertainties, and X-ray limits. For early-type galaxies with Mstar< 1010 M☉, we obtain a lower limit to the occupation fraction of >20% (at 95% confidence), but full occupation cannot be excluded. The preferred dependence of log LXupon log Mstarhas a slope of ∼0.7-0.8, consistent with the "downsizing" trend previously identified from the AMUSE data set, and a uniform Eddington efficiency is disfavored at ∼2σ. We provide guidelines for the future precision with which these parameters may be refined with larger or more sensitive samples.
black hole physics - galaxies: nuclei
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