University of Minnesota
School of Physics & Astronomy

Physics and Astronomy Calendar

Wednesday, April 22nd 2015
3:35 pm:
Speaker: Margaret J. Geller, Harvard-Smithsonian Center for Astrophysics
Subject: The Ultimate Mass of Galaxy Clusters
Refreshments served in Tate Foyer after colloquium. This is the more technical portion of the Van Vleck Lecture series. This lecture is free and open to the public.

Clusters of galaxies are still forming at the current epoch. At the turnaround radius, the infall velocity induced by the mass concentration in the cluster just balances the Hubble flow. In the standard cosmology, galaxies within the turnaround radius will remain bound to the cluster and the mass within this radius is a good estimator of the ultimate cluster mass. Our redshift survey of nearly 100 massive clusters (HeCS: Hectospec Cluster Survey) in the redshift range 0.1 to 0.3 enables a number of important cosmological probes. These include a test of the cluster mass proxy derived from observations of the Sunyaev-Zeldovich effect. These data also enable measurement of mass profiles to large radius using the caustic technique. These profiles enable direct measurement of the accretion rate of galaxy clusters and of their ultimate mass. These measurements are new and direct tests of our understanding
of the growth of structure in the universe.

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