Title: Kinematical evidence for an intermediate-mass black hole in M54
Author(s): Eva Noyola, Karl Gebhardt, Marcel Bergmann
Abstract: I will quickly review the kinematical evidence for globular
clusters that appear to host intermediate-mass black holes, focusing
mainly on G1 and omega Centauri. I will also present new results for
the Galactic globular cluster M54. This cluster lies at the center of
the tidally disrupted Sagittarius dwarf galaxy. It is still not clear
if M54 is actually the nucleus of the galaxy. We present two types of
velocity measurements for this object. First, we use GMOS at
GEMINI-south to obtain individual radial velocities for ~500 stars. We
do this, by combining a custom mask with a narrow filter which allows
to fit about 900 slits in a single exposure. We also use the GNIRS-IFU
at GEMINI-south, to obtain a velocity map for a 6"x4" field of view on
the cluster center, which we measured using the CO band head. The
combination of these two datasets indicates that the rotational
velocity and the velocity dispersion increase from the outskirts to
the center of the cluster. We combine the kinematical measurements
with photometry from HST in order to carry out orbit-based models,
with the aim of testing if the observed velocity rise is due to a
concentration of dark remnants or to the presence of an
intermediate-mass black hole. Our best fit model implies a central
black hole of 10,000 solar masses at the center of this cluster.