Measuring galaxy cluster temperatures and delensing for primordial non-Gaussianity

This seminar will cover two topics in Cosmic Microwave Background (CMB) research. First, I will present a recent measurement of the average temperature of galaxy clusters observed by the Atacama Cosmology Telescope using the relativistic thermal Sunyaev Zel'dovich (tSZ) effect. The relativistic motion of hot electrons in galaxy clusters introduces small corrections to the classic tSZ spectral distortion of the CMB. By detecting these corrections, we derive an average cluster temperature of 8.5 ± 2.4 keV. I will comment on how this type of measurement, in combination with other CMB-derived cluster properties, should inform future models of galaxy formation and evolution. In the second part, I will focus on primordial non-Gaussianity: the non-Gaussian properties of the universe's initial condition. Upcoming constraints from the CMB suffer from additional variance due to gravitational lensing. I will show preliminary results from the Planck data that demonstrate how the excess variance is partly mitigated by undoing the gravitational lensing in the CMB map. I will conclude by discussing the implications for future surveys.