Chandra Observations and the Dynamics of the Multiple Merger Cluster of Galaxies Abell 85

Joshua C. Kempner, Craig L. Sarazin (Unv. of Virginia), Paul M. Ricker (Univ. of Chicago)


Abstract

We have obtained Cycle 1 Chandra observations of the Abell 85 cluster of galaxies using the ACIS-I detector. Abell 85 is in the early stages of a multiple merger with two smaller subclusters, one impacting the main cluster from the south and one from the southwest. It also has a moderately strong cooling flow ( $\dot{M} = 108$ $M_{\odot}$/yr) associated with the main cluster center.

The southern subcluster contains the remnant of a cooling flow which has not been completely disrupted by the merger, similar to the ``cold fronts'' seen in Abell 2142 and Abell 3667. A possible bow shock precedes the cold front. We determine the relative merger velocity of the southern subcluster from the stagnation pressure at the cold front and from the standard Rankine-Hugoniot jump conditions at the bow shock. We then construct a model for the merger based on this kinematic information.

The smaller and less massive southwestern subcluster is host to a filamentary radio relic. We discuss possible scenarios for its formation.

We also examine the interaction between the AGN at the center of the main cluster cooling flow and the surrounding X-ray gas. The AGN appears to have excavated a cavity in the X-ray gas on at least one side of the AGN core. Several X-ray ``knots'' are also observed near the center of the cooling flow, perhaps indicating further interaction of the AGN with the gas in the cooling flow, or a cooling wake due to relative motion of the central galaxy and the intracluster gas.

CATEGORY: CLUSTERS OF GALAXIES



 

Himel Ghosh
2001-08-02