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Date and Time of the Query: 2019-06-18 T21:59:53 PDT
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For refcode 1999AJ....117..744V:
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Copyright by American Astronomical Society. Reproduced by permission
1999AJ....117..744V THE BLACK HOLE MASS DISTRIBUTION IN EARLY-TYPE GALAXIES: CUSPS IN HUBBLE SPACE TELESCOPE PHOTOMETRY INTERPRETED THROUGH ADIABATIC BLACK HOLE GROWTH ROELAND P. VAN DER MAREL Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 Received 1998 June 29; accepted 1998 November 2 ABSTRACT Hubble Space Telescope (HST) observations show that the surface brightness profiles of early-type galaxies have central cusps. I show that the observed characteristics of these cusps are consistent with the hypothesis that (1) all early-type galaxies have central black holes that grew adiabatically in homogeneous isothermal cores and (2) these "progenitor" cores followed scaling relations similar to those of the fundamental plane. The models studied here are the ones first proposed by P. Young. They predict I is proportional to r^-1/2^ at asymptotically small radii, but I is proportional to r^-{gamma}^ at the radii observable with HST. The slope {gamma} can take on all observed values and increases monotonically with {mu} = M_blackhole_/M_core_. Both "core" profiles (which have a break at a resolved radius and a shallow slope inside that radius) and "power-law" profiles (which have a steep slope down to the resolution limit and no clear break) can be reproduced. Observations show that, with few exceptions, galaxies with M_V_ < -22 have core profiles, and galaxies with M_V_ > -20.5 have power-law profiles; both profile types occur in galaxies with -22 < M_V_ < -20.5. For the models, the scaling relations for early-type galaxies imply that the progenitor core mass scales with luminosity as M_core_ is proportional to L^1.5^. If, as suggested by various arguments, the black hole (BH) mass M_blackhole_ scales roughly linearly with luminosity, M_blackhole_ is proportional to L, then {mu} is proportional to L^-0.5^. This yields larger cusp slopes in lower luminosity galaxies. Models with BH masses and progenitor cores that obey established scaling relations predict (at the distance of the Virgo Cluster) that galaxies with M_V_ < -21.2 have core profiles and galaxies with M_V_ > -21.2 have power-law profiles. This reproduces both the sense and the absolute magnitude of the observed transition. Intrinsic scatter in BH and galaxy properties can explain why both types of galaxies are observed around the transition magnitude. The observed bimodality in cusp slopes may be due to a bimodality in M_blackhole_/L, with rapidly rotating disky galaxies having larger M_blackhole_/L than slowly rotating boxy galaxies. I apply the models to 46 galaxies with published HST photometry. Both core and power-law galaxies are well fitted. The models suggest a roughly linear correlation between BH mass and V-band galaxy luminosity, log M_blackhole_ ~ -1.83 + log L in solar units (rms scatter 0.33 dex). This agrees with the average relation for nearby galaxies with kinematically determined BH masses. Photometrically and kinematically determined BH masses agree to within ~0.25 dex rms for galaxies that have both. These results provide additional support to the hypothesis that every galaxy (spheroid) has a central BH. The BH mass distribution inferred here is consistent with quasar statistics for a BH accretion efficiency of 4%. The proposed scenario is not a unique way to interpret the observed surface brightness cusps of galaxies, but it explains observational correlations that are otherwise unexplained, and it yields BH masses that agree with those determined kinematically. Key words: galaxies: elliptical and lenticular, cD-galaxies: kinematics and dynamics-galaxies: nuclei-galaxies: structure
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