Bulletin of the American Physical Society
2009 APS April Meeting
Volume 54, Number 4
Saturday–Tuesday, May 2–5, 2009; Denver, Colorado
Session J4: Merging Galaxies |
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Sponsoring Units: DAP GGR Chair: Scott Hughes, Masschusetts Institutue of Technology Room: Plaza F |
Sunday, May 3, 2009 1:30PM - 2:06PM |
J4.00001: Gas inflows in galaxy mergers as a key to the pairing, growth and formation of supermassive black holes Invited Speaker: Galaxy mergers are known to deliver a large fraction of the interstellar gas of galaxies towards the inner few hundred parsecs. The large resulting gas concentrations are of paramount importance to understand the fueling of central supermassive black holes, and may determine the conditions under which a pair of such black holes can sink and coalesce at the center of the merger remnant following a burst of gravitational waves. However, for a long time direct calculations that model the gravitational, hydrodynamical and radiative processes involved had only been able to hint qualitatively at the phenomenon of gas inflows, mostly due to their limited resolution in the nuclear region. Here I review the results of recent state-of-the art simulations performed with some of the largest parallel supercomputers available which have allowed to resolve scales of parsecs and below while the mergers of two galaxies takes place. I will show how the gas brought towards the central hundred parsecs produces a massive, star forming nuclear disk which compares well with recent observations of merger remnants in the nearby Universe. The numerical simulations demonstrate that a pair of supermassive black holes embedded in such nuclear disk can bind into binary on very short timescales, less than a million year. Whether the binary of supermassive black holes will easily be able to shrink down to the separation at which loss of energy via gravitational waves becomes the dominant process eroding its orbit is still under investigation. Moreover, in another calculation probing sub-parsec scales in the nuclear disk it is shown that more than a hundred million solar masses of gas can be transported to the inner parsec via torques driven by spiral instabilities. This strongly suggests not only that such disk torques are responsible for the fueling of supermassive black holes in galaxy mergers, but also that a massive black hole may form directly and rapidly from the collapse of a central gas cloud produced by the inflow. Direct, fast massive black hole formation may explain why bright quasars are seen to be in place already less than a billion year after the Big Bang. [Preview Abstract] |
Sunday, May 3, 2009 2:06PM - 2:42PM |
J4.00002: Black hole mergers along the cosmic history Invited Speaker: Galaxy mergers are an integral part of the structure evolution scenario. Massive black holes have inhabited the centers of galaxies since early cosmic times, when we detect them as the engines of luminous quasars. Mergers are therefore expected from the evolving population of massive black holes along the hierarchy of galaxy formation. I will discuss the expected properties of massive black hole mergers from early times to the present, and describe observational diagnostics that can shed light on the history of massive black holes. [Preview Abstract] |
Sunday, May 3, 2009 2:42PM - 3:18PM |
J4.00003: Probing Black Hole Mergers with LISA Invited Speaker: The Laser Interferometer Space Antenna (LISA) is a gravitational wave observatory in the frequency window 0.1 mHz - 0.1 Hz, capable of observing black hole mergers throughout the Universe. I will discuss the potential of LISA high-redshift surveys for novel studies of black hole demographics, formation of cosmic structures, cosmology and detailed investigations of the behaviour of gravity in the strong non-linear regime. [Preview Abstract] |
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