272 research outputs found
LISA Observations of Supermassive Black Hole Growth
Based on a high resolution cosmological n-body simulation, we track the
hierarchical growth of black holes in galaxy clusters from z=20 to z=0. We
present a census of black holes as function of redshift and will determine
their mass assembly history under a variety of assumptions regarding the
importance of gas accretion in black hole growth, from early supercritical
Eddington accretion to gas-poor hierarchical assembly. Following a galaxy
merger, black holes are expected to form, inspiral and merge after strongly
radiating energy via gravitational waves. For each binary black hole inspiral
and merger, we determine the expected gravitational wave signal for the Laser
Interferometer Space Antenna (LISA), and calculate the LISA event rate as a
function of time. We will calculate the black hole mass assembly history for
several black hole growth scenerios, so that we can explore tests to
characterize each model observationally. In particular, we will study how well
LISA observations will be able to distinguish between these very different
assembly scenarios.Comment: 5 pages, 11 figures, proceedings, Sixth International LISA Symposium,
June 19-23, 2006 Goddard Space Flight Center Greenbelt, Marylan
Event Rate for Extreme Mass Ratio Burst Signals in the LISA Band
Stellar mass compact objects in short period orbits about a
-- solar mass massive black hole (MBH) are thought to be a
significant continuous-wave source of gravitational radiation for the ESA/NASA
Laser Interferometer Space Antenna (LISA) gravitational wave detector. However,
these extreme mass-ratio inspiral sources began in long-period, nearly
parabolic orbits that have multiple close encounters with the MBH. The
gravitational radiation emitted during these close encounters may be detectable
by LISA as a gravitational wave burst if the characteristic passage timescale
is less than seconds. Scaling a static, spherical model to the size and
mass of the Milky Way bulge we estimate an event rate of ~ 15 per year for such
burst signals, detectable by LISA with signal-to-noise greater than five,
originating in our galaxy. When extended to include Virgo cluster galaxies our
estimate increases to a gravitational wave burst rate of ~ 18. We conclude that
these extreme mass-ratio burst sources may be a steady and significant source
of gravitational radiation in the LISA data streams.Comment: 4 pages, minor revisions. Accepted for ApJ Letter
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