We investigate the differences in the M• σ relation derived recently by Ferrarese & Merritt and by Gebhardt and collaborators. The shallower slope found by the latter authors (3.75 vs. 4.8) is due partly to the use of a regression algorithm that ignores measurement errors, and partly to the value of the velocity dispersion adopted for a single galaxy, the MilkyWay. A steeper relation is shown to provide a better fit to black hole masses derived from reverberation mapping studies. Combining the stellar dynamical, gas dynamical, and reverberation mapping mass estimates, we derive a best-fit relation M• = 1.30(±0.36)×10^8M⊙(σc/200 km s1)^(4.72(±0.36) )(Refer to PDF file for exact formulas).
Department, Program, or Center
School of Physics and Astronomy (COS)
Astrophysical Journal 2001 January 20 vol. 547, no. 1, 140
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