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Institute of Advanced Study

Professor Nicholas Kaiser

COFUND Senior Research Fellow at Hatfield College, Durham University (June - July 2014)

Prof Nicholas Kaiser (FRS) is an Astronomer at the Institute for Astronomy, University of Hawaii, USA, Associate Director for National Telescope Projects, Principal Investigator, Pan-STARRS. He is a world renowned expert in the field of galaxy cluster research. His contributions to cosmology are truly innovative and outstanding (including pioneering work in modelling the galaxy distribution in redshift space and weak gravitational lensing). In recent years he has headed the Pan-STARRS1 survey as the Pan-STARRS PI. His contribution was recognised when he was made a Fellow of the Royal Society in 2008.

The collaborative project proposed seeks to quantify systematic errors in estimating the masses of stacked galaxy clusters. As there are typically only a few galaxies with measured redshifts (velocities) per galaxy cluster, a standard approach is to combine many (similar) clusters to form a stack and then analyse this composite cluster. The composite is accurately spherically symmetric and in near equilibrium. However the standard method of applying Jeans’ equation to such a composite is incorrect as it ignores the fact that the individual clusters making up the stack are not relaxed nor spherically symmetric. The collaborators have developed the correct theoretical framework to describe such composites. They now intend to use start-of-the-art N-body cosmological simulations of galaxy clusters (run at the ICC) to quantify the biases that exist in current cluster mass estimates.

The results will have implications for fundamental cosmological parameters such as the amount of Dark Matter and Dark Energy as these are constrained by galaxy clusters and their evolution.

“Over the years I have had numerous interactions and collaborations with astronomers in Durham. My visit this summer has helped cement these links and is leading to fruitful new directions of research.”

Professor Nicholas Kaiser, University of Honolulu