Black hole ejections in galaxy mergers
Session 33 -- Relativistic Astrophysics
Display presentation, Tuesday, 31, 1994, 9:20-6:30

## [33.05] Black hole ejections in galaxy mergers

M.J.Valtonen,S.Mikkola,P.Hein\"am\"aki (Tuorla Obs)

Due to mergers of galaxies, supermassive black holes are expected to appear in binary pairs in centers of giant galaxies. When these galaxies merge, typically a four black hole interaction begins. In this work the orbits of black holes are calculated until collisions reduce the number of black holes to two, or until the system breaks up due to ejection of black holes. The ejections are classified as two-sided or one-sided depending on whether only one black hole or two black holes escape from the galaxy, respectively. The two sided ejections are further divided in triples and doubles depending on whether a black hole remains in the galaxy or not. The following table (column~1) summarizes the numbers of different end results in a typical case.

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\begin{tabular}{lrrr} ~ & (1) & (2) & (3) \\ ~~~~~~~~Triples & 18.5\% & 65\% & 61\% \\ ~~~~~~~~Doubles & 0.5\% & 13\% & 13\% \\ ~~~~~~~~One-Sided & 78\% & 22\% & 5\% \\ ~~~~~~~~Single & 3\% & -- & 21\% \end{tabular}

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\noindent The last line `single' refers to systems where no black holes escaped. We assume that the black holes possess accretion disks and possibly jets and are thus observable. In the first place we try to make an association with extended radio sources. Since radio sources samples (such as 3C) have strong selection biases, we select subsamples from our data using similar selection biases as are known to exist in observed samples. Column~2 gives an example of such a subsample. The last column gives the corresponding data for the 3C sample. We note that the agreement between columns 2 and 3 is quite good assuming that many one-sided extended double radio sources have been wrongly classified as single component sources. A video tape of four black hole orbits is shown.