Binary and Single Galaxies in Clusters

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Session 125 -- Structure of Clusters of Galaxies
Oral presentation, Saturday, January 15, 2:15-3:45, Crystal Forum Room (Crystal City Marriott)

[125.05] Binary and Single Galaxies in Clusters

P.S.S.Ip, C.C.Dyer (U. Toronto)

CCD images of 5 ``binary-rich'' clusters of galaxies indicate that about half of the ``binaries'' are star-galaxy or star-star pairs. These clusters are not binary-rich.

$N$-body simulations of binary galaxies in a fixed cluster potential show that either the binary merges in a time similar to that of the isolated binary or that the binary is disrupted. A moderately good predictor of whether the binary merges or is disrupted is the mean torque exerted by the cluster over a quarter of the initial binary period. There is a substantial amount of mass loss in many cases.

Simulations of single galaxies in the same orbits as the binaries show that the mass loss is due primarily to the cluster potential, and not to an interplay between the cluster and the binary. A simple model based on that of Spitzer (1987) matches the results moderately well.

Saturday program listing