Constraints on Cosmology and the Physics of the Intracluster Medium from Secondary Anisotropies in the Cosmic Microwave Background

Abstract

This thesis presents a number of new statistical approaches to

constrain cosmology and the physics of the intracluster medium (ICM)

using measurements of secondary anisotropies in the cosmic microwave

background (CMB), the remnant thermal radiation left over from the Big

Bang that still permeates the universe today. In particular, I

consider the thermal Sunyaev-Zel'dovich (tSZ) effect, in which the

hot, ionized gas in massive galaxy clusters casts a ``shadow'' against

the CMB, and gravitational lensing of the CMB, in which the gravity of

intervening structures bends the path of CMB photons as they travel to

us from the early universe. I use data from the Planck satellite to

obtain the first detection of the tSZ -- CMB lensing cross-power

spectrum, a signal which is sensitive to a previously unstudied

population of high-redshift, low-mass groups and clusters. I combine

this measurement with Planck measurements of the tSZ power spectrum to

obtain cosmological and astrophysical constraints, and also

investigate the ability of future tSZ power spectrum measurements to

constrain primordial non-Gaussianity and the sum of the neutrino

masses. In addition to these power spectrum measurements, I also

present new techniques to obtain cosmological and astrophysical

constraints from non-Gaussian statistics of the tSZ signal, starting

with the tSZ skewness and proceeding to consider the entire one-point

PDF of the tSZ field. I apply these methods to data from the Atacama

Cosmology Telescope, yielding some of the tightest constraints yet

achieved on the amplitude of cosmic matter density fluctuations.

Moreover, these methods allow the long-standing degeneracy between

cosmology and ICM physics to be directly broken with tSZ data alone

for the first time.