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arXiv · astro-ph/9708072

The Demography of Massive Dark Objects in Galaxy Centres

John Magorrian·Scott Tremaine·Douglas Richstone·Ralf Bender·Gary Bower·Alan Dressler·S. M. Faber·Karl Gebhardt·Richard Green·Carl Grillmair·John Kormendy·Tod Lauer
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Abstract

We construct dynamical models for a sample of 36 nearby galaxies with Hubble Space Telescope photometry and ground-based kinematics. The models assume that each galaxy is axisymmetric, with a two-integral distribution function, arbitrary inclination angle, a position-independent stellar mass-to-light ratio Upsilon, and a central massive dark object (MDO) of arbitrary mass M_bh. They provide acceptable fits to 32 of the galaxies for some value of M_bh and Upsilon; the four galaxies that cannot be fit have kinematically decoupled cores. The mass-to-light ratios inferred for the 32 well-fit galaxies are consistent with the fundamental plane correlation Upsilon \propto L^0.2, where L is galaxy luminosity. In all but six galaxies the models require at the 95% confidence level an MDO of mass M_bh ~ 0.006 M_bulge = 0.006 Upsilon L. Five of the six galaxies consistent with M_bh=0 are also consistent with this correlation. The other (NGC 7332) has a much stronger upper limit on M_bh. We consider various parameterizations for the probability distribution describing the correlation of the masses of these MDOs with other galaxy properties. One of the best models can be summarized thus: a fraction f ~0.97 of galaxies have MDOs, whose masses are well described by a Gaussian distribution in log (M_bh/M_bulge) of mean -2.27 and width ~0.07.

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John Magorrian, Scott Tremaine, Douglas Richstone, Ralf Bender, Gary Bower, Alan Dressler, S. M. Faber, Karl Gebhardt, Richard Green, Carl Grillmair, John Kormendy, Tod Lauer. 1997-08-07. The Demography of Massive Dark Objects in Galaxy Centres. https://doi.org/10.1086/300353

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