Speaker
Description
Many of our strongest constraints on the cosmological model come from analysis of the Cosmic Microwave Background formed at high redshift in the early universe. Low-redshift cosmological tests are fundamentally important, however, as they test different regimes of time, scale and curvature. The abundance of galaxy clusters is one such test, constraining the product of the amplitude of fluctuations present in the matter distribution at early times, and the amount by which this amplitude has grown down to the present day. The degeneracy between these two factors limits the precision of abundance constraints. A few years ago, we pointed out that measurements of the instantaneous growth rate of clusters could break this degeneracy. Recently, we have proposed and implemented one way of doing this in practice, using weak gravitational lensing measurements of the “infall zone”. I will discuss this test and other recent work on cluster structure and evolution based on data from the UNIONS and Euclid-Wide surveys.
