Measuring the Growth of Structure with Millimeter-Wavelength Surveys

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Dr. Neelima Sehgal is awarded an NSF Astronomy and Astrophysics Postdoctoral Fellowship to carry out a program of research and education at Princeton University. Ground-based millimeter-wavelength surveys are underway and are detecting tens to hundreds of galaxy clusters by their Sunyaev-Zel'dovich (SZ) signal, in which high-energy electrons distort the cosmic microwave background radiation (CMB) through inverse Compton scattering, in which the low energy CMB photons receive energy boost during collision with the high energy cluster electrons. These surveys have presented their first measurements of the cluster number density evolution over cosmic time and can potentially provide precision measurements of structure growth. This, in turn, could discriminate between dark energy as a component of the Universe or as a manifestation of General Relativity's failure on the largest scales. Dr. Sehgal will build on her previous work to lead an analysis of the first cosmological constraints from an SZ-selected sample of galaxy clusters detected with the Atacama Cosmology Telescope. She will play a leading role in the determination of cosmological parameters from larger and more sensitive SZ cluster surveys and in upgrading simulations of the millimeter-wavelength sky by calibrating to the latest multi-wavelength observations. The latter will help reduce sources of systematic uncertainty in the cosmological analysis. Dr. Sehgal will also explore the feasibility of measuring cluster peculiar velocities using millimeter-wave simulations and thereby assess their utility as an alternative probe of structure growth.Dr. Sehgal will also work with the New Jersey Astronomy Center for Education to develop and support several series of class modules that teach high-school students about key concepts in cosmology. She will also train high-school teachers on the use of these modules and assess their effectiveness through surveys. These modules will be distributed to high-schools nationwide.