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C.A. Onken (The Ohio State University)
To establish a statistical calibration between black hole masses determined for quiescent galaxies and those determined in active galaxies (AGNs) by reverberation mapping, we have scaled the reverberation masses in order to match the quiescent galaxy correlation between black hole mass and bulge stellar velocity dispersion, the M-sigma relation. Black hole masses in some AGNs can be measured via reverberation mapping, which traces the response of emission-line gas in the broad-line region (BLR) to variations in the ionizing continuum of the AGN, but these estimates are subject to a systematic uncertainty arising from our lack of knowledge of the structure and kinematics of the BLR. Quiescent galaxies, in which the black hole masses have been determined by other techniques, should not be subject to this same type of uncertainty. We have used revised reverberation-mapping results and measurements of sigma in 16 AGNs to estimate the average factor that scales reverberation masses to match the M-sigma relation defined for quiescent galaxies. In doing so, we provide an empirical calibration for black hole masses determined by reverberation mapping.
An independent means of intercalibrating these black hole mass measurement techniques is to apply multiple methods to the same galaxy, something which has yet to be done for a reverberation- mapped AGN. We have undertaken a project to measure the black hole mass in a nearby AGN, NGC 4151, with stellar dynamics. Combining ground-based and HST observations of stellar absorption lines, we are working to constrain the black hole mass, which we will then compare to a new determination of the reverberation mass. The calibration for NGC 4151 will be an important point of comparison relative to the average calibration described above, and will begin to provide needed limits on the parameters of BLR models.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.