Hubble Space Telescope (HST) images and spectra of the nucleated dwarf elliptical galaxy NGC 205 are combined with 3-integral axisymmetric dynamical models to constrain the mass MBH of a putative nuclear black hole. This is only the second attempt, after M33, to use resolved stellar kinematics to search for a nuclear black hole with mass below 106 solar masses. We are unable to identify a best-fit value of MBH in NGC 205; however, the data impose a upper limit of 2.2×104M⊙ (1σ confidence) and and upper limit of 3.8×104M⊙ (3σ confidence). This upper limit is consistent with the extrapolation of the MBH − σ relation to the MBH < 106M⊙ regime. If we assume that NGC 205 and M33 both contain nuclear black holes, the upper limits on MBH in the two galaxies imply a slope of 5.5 or greater for the MBH − σ relation. We use our 3-integral models to evaluate the relaxation time and stellar collision time in NGC 205; Tr is 108 yr or less in the nucleus and Tcoll 1011 yr. The low value of Tr is consistent with core collapse having already occurred, but we are unable to draw conclusions from nuclear morphology about the presence or absence of a massive black hole. (Refer to PDF file for exact formulas).

Publication Date



This is the pre-print of an article published by the American Astronomical Society. The final, published version is located here: https://doi.org/10.1086/430752

© 2005 The American Astronomical Society.

Also archived In: arXiv: astro-ph/0502493 v2 12 Apr 2005

This work was supported by STScI grant GO-09448 and grants AST-0206031, AST- 0420920 and AST-0437519 from the NSF and grant NNG04GJ48G from NASA.

Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works in February 2014.

Document Type


Department, Program, or Center

School of Physics and Astronomy (COS)


RIT – Main Campus