Cosmology from Secondary Anisotropies of the Cosmic Microwave Background

Abstract

Gravitational lensing and the Sunyaev-Zel'dovich effect introduce new intensity fluctuations, known as secondary anisotropies, into the cosmic microwave background radiation (CMB). These CMB secondary anisotropies encode a wealth of information about the distribution of dark matter and gas throughout our universe. In this thesis, we present novel measurements of CMB lensing and the Sunyaev-Zel'dovich effect in the microwave background and use them to place new constraints on cosmology.

In an early thesis chapter, we describe the first detection of the power spectrum of gravitational lensing of the CMB. The power spectrum is detected at a four sigma significance through a measurement of the four-point correlation function of Atacama Cosmology Telescope (ACT) CMB temperature maps. This first detection gravitationally probes the amplitude of large-scale structure at redshifts ~1-3 to 12% accuracy, and lies at the beginning of an exciting new field of science with the lensing power spectrum.

From this measurement of the CMB lensing power spectrum we extract first cosmological constraints. We explain in detail how the amount of dark energy in our universe affects the amplitude of the lensing signal by modifying both the geometry of the universe and the growth of structure. We then demonstrate that our lensing measurements provide, for the first time, evidence for the existence of dark energy from the CMB alone, at a 3.2 sigma significance.

We use CMB lensing measurements to study the relation of quasars to the underlying distribution of dark matter. Detecting the cross-power of CMB lensing with the spatial distribution of quasars and hence measuring the quasar bias to within 25%, we obtain a measurement of the characteristic dark matter halo mass of these objects.

CMB lensing power spectrum measurements typically require the subtraction of a simulated bias term, which complicates the analysis; we develop new techniques to obviate this bias subtraction.

Finally, we develop a novel method for measuring the Sunyaev-Zel'dovich effect through the skewness it induces in CMB temperature maps. Detecting this skewness in ACT CMB maps for the first time at five sigma significance, we demonstrate how this novel measurement constrains the amplitude of structure in our universe to within 4%.