Is Cold Dark Matter Still a Strong Buy? The Lesson from Galaxy Clusters

Abstract

For the last few years the Cold Dark Matter model (ticker: CDM), has been the dominant theory of structure formation. We briefly review the recent advancements and predictions of the model in the field of galaxy clusters. A new set of very high resolution simulations of galaxy clusters show that they have (1) density profiles with central slopes very close to -1.6 and (2) abundance of subhalos similar to the ones observed in real clusters. These results show a remarkably small cluster to cluster variation and a weak dependence from the particular CDM cosmology chosen (LCDM having ~40% less substructure than SCDM). While still a speculative theory with a high prediction/evidence ratio, subject to strong challenges from observational data and competition from other hierarchical theories, we give CDM a rating of ``market outperform'' and of ``long term BUY''.

12 pages, 6 figures. Contribution to `Astrophysical Ages and Timescales' ASP Con f. Ser., Eds. T. von Hippel, N. Manset, C. Simpson. Available also at http://www.merate.mi.astro.it/~fabio