Deconstructing A3266: A Major Merger in a Quiet Cluster

Abstract

We present results of simple N-body simulations that strengthen the suggestion that A3266 is composed of two subunits of comparable mass that have recently merged. Both the real cluster and the N-body dark-matter cluster show mixed signals of substructure under statistical tests. However, in a decidedly non-statistical approach allowed by the wide-area coverage and large number of redshifts they measured in A3266, Quintana, Ramirez, and Way (1996; QRW) sliced the real cluster in redshift space to uncover a peculiar spatial distribution of galaxies that they suggested was the result of a recent merger. In our simulations, a similar distribution is the result of an ongoing merger between two comparable-mass units that started about 2x10^9 years ago in the N-body simulations. We also find that the distribution of emission line galaxies in A3266 traces the same structure. We discuss further tests of our merger hypothesis, and speculate on the possibility that a similar process might be occurring in other, apparently-relaxed clusters at the present epoch.