Cosmology from Sunyaev-Zeldovich Cluster Abundance

May 15, 2018 - 12:15 pm to 1:15 pm

Campus, PAB 232

Chun-Hao To

The abundance of galaxy clusters is a powerful cosmological probe since it depends both on the expansion history of the Universe and the growth of density fluctuations. In recent years, cosmological constraints from cluster abundance have been advanced significantly from clusters identified in X-ray, optical and millimeter wavelengths. In millimeter wavelength, the dominant signals from galaxy clusters arise from thermal Sunyaev-Zeldovich (t-SZ) effect, the small spectral distortion of the CMB spectrum caused by scattering of the CMB photons off high energy electrons in galaxy clusters. The t-SZ effect allows researchers to detect clusters with a mass limit that is independent of redshifts of clusters. Therefore, t-SZ cluster samples are powerful on constraining the redshift evolution of cluster abundance, which is directly dependent on the underlying cosmology and can be used to determine the equation of state of the dark energy. 


In this talk I’ll first describe the physics of t-SZ effect and how it allows galaxy clusters to leave imprints on CMB maps. I’ll then describe how researchers constrain cosmological parameters form clusters identified on CMB maps. In this part, I’ll use the galaxy clusters identified from SPT-SZ survey as an example, and show how researchers use X-ray data to calibrate tSZ mass proxies. I’ll conclude this part by showing what is the current constraint on cosmological parameters form this specific probe and how it compares to other cosmological probes. In the last part of my talk, I’ll discuss how the SPT-3G and the upcoming CMB S4 experiment will improve the constraints.