A Black Hole Mass Determination for the Compact Galaxy Mrk 1216
  Mrk 1216 is a nearby, early-type galaxy with a small effective radius of 2.8
kpc and a large stellar velocity dispersion of 308 km/s for its K-band
luminosity of 1.4x10^11 L_sun. Using integral-field spectroscopy assisted by
adaptive optics from Gemini North, we measure spatially resolved stellar
kinematics within ~450 pc of the galaxy nucleus. The galaxy exhibits regular
rotation with velocities of \pm 180 km/s and a sharply peaked velocity
dispersion profile that reaches 425 km/s at the center. We fit axisymmetric,
orbit-based dynamical models to the combination of these high angular
resolution kinematics, large-scale kinematics extending to roughly three
effective radii, and Hubble Space Telescope imaging, resulting in a constraint
of the mass of the central black hole in Mrk 1216. After exploring several
possible sources of systematics that commonly affect stellar-dynamical black
hole mass measurements, we find a black hole mass of (4.9\pm1.7)x10^9 M_sun and
a H-band stellar mass-to-light ratio of 1.3\pm0.4 M_sun/L_sun (1-sigma
uncertainties). Mrk 1216 is consistent with the local black hole mass - stellar
velocity dispersion relation, but is a factor of ~5-10 larger than expectations
from the black hole mass - bulge luminosity and black hole mass - bulge mass
correlations when conservatively using the galaxy's total luminosity or stellar
mass. This behavior is quite similar to the extensively studied compact galaxy
NGC 1277. Resembling the z~2 quiescent galaxies, Mrk 1216 may be a passively
evolved descendant, and perhaps reflects a previous era when galaxies contained
over-massive black holes relative to their bulge luminosities/masses, and the
growth of host galaxies had yet to catch up.
