Figure: Mean velocity and velocity dispersion of M32

This figure shows the mean velocity and velocity dispersion as function of distance from the centre, along various axis for the elliptical galaxy M32. Three telescopes were used to obtain these data: the Hubble Space Telescope (HST), the Canada-France-Hawaii Telescope (CFHT) and the William Herschel Telescope (WHT), along the major, minor and intermediate axis. The HST data have the best spatial resolution and cover the very centre of the galaxy (inner 0.5 arcseconds). Such data are therefore most helpful to constrain the black hole mass.

Along with the data are shown the predictions of four dynamical orbit models with different black hole masses. The best fit model (model C) has a 3.4 · 10⁶ solar masses black hole in the center. The model with no black hole (model A) can not explain the data, in particular the high central velocity dispersion as observed by HST.

Credit: Figure 8 in "Improved evidence for a black hole in M32 from HST/FOS spectra - II. Axisymmetric dynamical models", by van der Marel R.P., Cretton N., de Zeeuw P.T., Rix H.W., Astrophysical Journal, 493, 613-631, 1998.
© 1998. The American Astronomical Society. All Rights Reserved.

This article is available in pdf or ps format here.