The Low End of the Supermassive Black Hole Mass Function: Constraining the Mass of a Nuclear Black Hole in NGC 205 via Stellar Kinematics

• Published in: The Astrophysical journal 2005-07, Vol.628 (1), p.137-152
• Main Authors: Valluri, Monica, Ferrarese, Laura, Merritt, David, Joseph, Charles L
• Format: Article
• Language: English
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1086/430752

Hubble Space Telescope (HST) images and spectra of the nucleated dwarf elliptical galaxy NGC 205 are combined with three-integral axisymmetric dynamical models to constrain the mass M sub(BH) 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 10 super(6) solar masses. We are unable to identify a best-fit value of M sub(BH) in NGC 205; however, the data impose a upper limit of 2.2 x 10 super(4) M sub( )(1 s confidence) and an upper limit of 3.8 x 10 super(4) M sub( )(3 s confidence). This upper limit is consistent with the extrapolation of the M sub(BH)-s relation to the M sub(BH) < 10 super(6) M sub( )regime. If we assume that NGC 205 and M33 both contain nuclear black holes, the upper limits on M sub(BH) in the two galaxies imply a slope of 65.5 or greater for the M sub(BH)-s relation. We use our three-integral models to evaluate the relaxation time and stellar collision time in NGC 205; T sub(r) is 610 super(8) yr or less in the nucleus, and T sub(coll)-10 super(11) yr. The low value of T sub(r) 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.