Astrophysics

The next frontiers in cosmic microwave background (CMB) science include a detailed mapping of the CMB polarization anisotropy, with goals of detecting the inflationary B-mode signal and reconstructing high-fidelity maps of the matter distribution via CMB lensing, as well as a first detection of CMB spectral distortions.  At this level of precision (~nK), Galactic and extragalactic foregrounds may be the ultimate limiting factor in deriving cosmological constraints.  I will discuss biases due to foregrounds in CMB lensing measurements, including the first calculation of the lensing bias due to the kinematic Sunyaev-Zel’dovich effect, as well as recent progress in developing novel foreground-free CMB lensing estimators.  I will then present methods to extend CMB foreground parameterizations in a systematic, flexible way, with applications to both polarization and spectral distortion measurements.  Using this framework, I will discuss spectral distortion forecasts for CMB spectrometer mission concepts, showing that high-significance measurements of the Compton-y and relativistic thermal Sunyaev-Zel’dovich signals can be expected, as well as a potential detection of the primordial mu-type distortion due to Silk damping of small-scale acoustic modes.

Gravitational lensing of the cosmic microwave background has emerged as a powerful cosmological probe, made possible by the development and characterization of nearly-optimal estimators for extracting the lensing signal from temperature and polarization maps. One can ask whether similar tools can be applied to upcoming "intensity maps" of emission lines at other wavelengths (e.g. 21cm). In this talk, I will present recent work in this direction, focusing in particular on the impact of gravitational nonlinearities on standard quadratic lensing estimators. I will show how these nonlinearities can provide a significant contaminant to lensing reconstruction, even for observations at reionization-era redshifts, but will also describe how this contamination can largely be mitigated by modifying the lensing estimator. Finally, I will present estimates for the detectability of lensing in ongoing and future intensity mapping surveys.