Towards testing CMB anomalies using the kinetic and polarized Sunyaev-Zel’dovich effects

Abstract

Measurements of the cosmic microwave background (CMB) temperature anisotropies on large angular scales have uncovered a number of anomalous features of marginal statistical significance, such as a hemispherical power asymmetry, a lack of power on large angular scales, and features in the power spectrum. Because the primary CMB temperature, the power spectrum has been measured at the cosmic variance limit; determining if these anomalies are hints of new physics as opposed to foregrounds, systematics, or simply statistical flukes requires new observables. In this paper, we highlight the potential contribution that future measurements of the kinetic Sunyaev-Zel'dovich effect (kSZ) and the polarized Sunyaev-Zel'dovich effect (pSZ) could make in determining the physical nature of several CMB anomalies. The kSZ and pSZ effects, temperature, and polarization anisotropies induced by scattering from free electrons in the reionized Universe are the dominant blackbody contribution to the CMB on small angular scales. Using the technique of SZ tomography, measurements of kSZ and pSZ effects can be combined with galaxy surveys to reconstruct the remote CMB dipole and quadrupole fields, providing a three-dimensional probe of large scale modes inside our Hubble volume. Building on previous work, we forecast the additional constraining power that these observables might offer for a representative set of anomaly models in the scenario of idealized next-generation CMB experiments and galaxy surveys. We find that the remote CMB dipole and quadrupole can yield constraints on anomalies models significantly beyond what can be done with CMB temperature and polarization on large scales, and comparable to what is possible with a large photometric galaxy survey. The best constraints are obtained from a multitracer analysis including the primary CMB, remote fields and galaxy survey.

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