Measuring the Masses of Black Holes in the Nuclei of Nearby Galaxies

Aaron Barth
Center for Astrophysics


Massive dark objects, most likely supermassive black holes, have now
been detected in the nuclei of many nearby galaxies.  The tight
correlation recently discovered between the black hole mass and the
stellar velocity dispersion of the host galaxy points to an intimate
connection between the formation of galaxy bulges and the growth of
the central black holes via accretion.  The observational challenge
now is to measure the masses of the black holes with sufficient
precision that specific models for black hole formation and growth can
be tested.  I will discuss new results from a project designed to
measure the central masses in a sample of nearby galaxies, using
Hubble Space Telescope observations of rotating, circumnuclear disks
of ionized gas.  New modeling techniques have been developed to
simulate the HST observations in detail, so that accurate masses and
meaningful error bars can be derived from the data.  These techniques
will be illustrated for the case of the S0 galaxy NGC 3245, in which
we have detected a black hole of 2.1x10^8 solar masses.