Nancy A. Levenson
Science Highlights
This issue’s Science Highlights focuses on black holes of various sizes
starting with an ultracompact dwarf galaxy hosting an unexpectedly
large supermassive black hole, followed by a stellar tidal disruption
event caused by a moderate-mass black hole, and finally tests of black
hole mass measurements in an active galaxy.
The Origin of an Ultracompact Dwarf Galaxy and Its Black Hole
Figure 1.
The black hole mass
is derived from
dynamical modeling,
where the stellar CO
bandhead provides
the kinematic
information. This
figure shows the
goodness-of-fit
measurement
considering variations
in black hole mass
and stellar mass-tolight ratio, calculated
at the discrete green
points. Contours
mark the 1, 2, and 3σ
confidence levels.
8
Peering into the center of an ultracompact dwarf (UCD) galaxy, Anil Seth (University of Utah)
and collaborators found an unexpectedly large supermassive black hole. Using the Nearinfrared Integral Field Spectrometer (NIFS) and the laser guide star adaptive optics system
on Gemini North, the team obtained high spatial resolution
kinematic data to measure the
black hole’s mass, of 21 million
solar masses. This accounts for
15 percent of the total mass of
the galaxy and makes this object, called M60-UCD1, the lowest mass galaxy known to host a
supermassive black hole.
UCDs are extremely dense,
showing some similarities to
globular clusters, which raises
the question of their origin. Are
they massive versions of ordinary globular clusters, or did
GeminiFocus
October 2014