Colin Hill

New Information in Ancient Photons: Novel Approaches to CMB Secondary Anisotropies

Cosmic microwave background (CMB) experiments have recently entered a new era in which cosmological and astrophysical constraints derived from the secondary anisotropies (due to late-time effects) substantially improve upon those derived from the primary anisotropies alone. In this talk, I will discuss new approaches to extract information from these signals, placed in the broader context of component separation in CMB analysis. I will describe novel methods for studying the thermal Sunyaev-Zel'dovich (SZ) effect --- the inverse-Compton scattering of CMB photons off hot electrons --- using cross-correlations, stacking, and beyond-Gaussian statistics. I will present projections for thermal SZ extraction from Advanced ACT data based on a new component-separation pipeline, as well as new foreground-marginalized forecasts for the all-sky tSZ (and $\mu$) spectral distortion monopole from the proposed PIXIE satellite. I will then present a measurement of the kinematic SZ effect (due to electrons moving with a net bulk velocity along the line-of-sight) with Planck, WMAP, and WISE data using a novel estimator that does not require redshift estimates for individual tracers. This measurement yields the tightest kinematic SZ-derived constraint on the low-redshift baryon fraction to date. The result is consistent with constraints derived from the primary CMB and Big Bang nucleosynthesis, thus resolving the long-standing "missing baryon problem".