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November 2 (4:00PM) in the 2nd Floor Conference Room in Dearborn Speaker: Loren Hoffman (Harvard) “Consequences of 3-black hole interactions in hierarchically merging massive galaxies.” Hierarchical structure formation, when combined with the observation that nearly all galaxies with significant bulge components host supermassive black holes (SMBH), leads directly to the formation of BH binaries. If the binary coalescence time exceeds the typical time between mergers, then some galactic nuclei should contain three or more SMBH. The “downsizing” of actively star-forming galaxies leads to passive evolution of large galaxies at late times, permitting the formation of low-density nuclei conducive to the survival of BH binaries. We performed a series of simulations to study the outcomes triple-BH encounters in galactic nuclei using physically-motivated initial BH configurations, BH mass distributions, and galactic models typical for cored giant elliptical galaxies. The results that I will discuss include the efficiency of coalescence induced by the encounters; the predicted semi-major axis and eccentricity distribution of observed binaries if three-body interactions are prevalent; the statistics of wandering black holes ejected during the encounters; the distribution of the distances of closest approach between pairs during the close encounters and implications for the possible observability of wandering BH; and the extent of core scouring caused by the 3-body systems. |