Astrophysics Seminar: Probing Lambda CDM and the nature of DM with Dynamics of cluster galaxies

Abstract:

In the first part of the talk I will present results from a dynamical analysis of 7 galaxy clusters (0.13 < z < 0.45), with an average of 286 galaxies per cluster (identified from measured line-of-sight velocities). We derived the clusters' masses, and for each cluster we also identified infalling and accreted halos and estimated their masses. From the cluster and halo masses we estimated the contribution of different mass ratios to halo growth, a key aspect of the evolution of the large-scale structure. Our estimates are in agreement with expectations from results of the Millennium simulation.

In the second part of the talk, I will show how we can study the nature of DM using galaxy dynamics. Until recently, the mass distribution of DM was its only property that could be inferred from simulations and tested against observational data. The full phase-space is clearly important for determining the nature of DM. I will describe how we indirectly deduced DM velocity anisotropy profiles in clusters. These profiles were found to be different from those of some 6000 cluster-size halos (at redshift zero) identified in a \Lambda CDM hydrodynamical simulation. I will speculate on the possible cause for this difference.

Seminar Organiser: Prof. Rennan Barkana