PROPERTIES OF CLUSTERS OF GALAXIES

Recent results on clusters are reviewed and discussed in relation to cooling flows. Mergers of subclusters are apparently common in clusters. Such mergers will tend to disrupt cooling flows. I suggest that the recently observed luminous arcs in clusters may be shocks generated by a subcluster merger in a cluster with a cooling flow. The peaked galaxy distributions and radial orbits suggested by recent studies of clusters will lead to a larger number of rapidly moving galaxies passing through the cooling flow region, and this may affect the cooling flow. Recent studies of the mass distributions in clusters suggest that the dark matter is centrally condensed; this may indicate that it is dissipative and baryonic. I suggest that this dark matter and the ultimate reservoir of the cooling gas in cooling flows may both be low mass star or planetary objects. Finally, I discuss various ways in which the cooling flow environment, which appears to be ubiquitous in the early-type galactic systems which form the hosts for strong radio sources, may affect the origin and structure of the radio emitting regions.

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