Will Kinematic Sunyaev-Zel'dovich Measurements Enhance the Science Return from Galaxy Redshift Surveys?

TL;DR

Future CMB experiments can significantly enhance cosmological constraints by combining kSZ measurements with galaxy surveys, especially when considering anisotropic signals and marginalizing over optical depth uncertainties.

Contribution

This paper demonstrates how to extract and utilize anisotropic kSZ signals from future CMB data to improve measurements of cosmic growth and expansion rates, accounting for optical depth uncertainties.

Findings

Combining kSZ and galaxy data reduces errors on H and f by 50-70%.

Anisotropic kSZ signals contain significant cosmological information.

Marginalizing over optical depth uncertainties is crucial for realistic constraints.

Abstract

Yes. Future CMB experiments such as Advanced ACTPol and CMB-S4 should achieve measurements with S/N of $> 0.1$ for the typical galaxies in redshift surveys. These measurements will provide complementary measurements of the growth rate of large scale structure $f$ and the expansion rate of the Universe $H$ to galaxy clustering measurements. This paper emphasizes that there is significant information in the anisotropy of the relative pairwise kSZ measurements. We expand the relative pairwise kSZ power spectrum in Legendre polynomials and consider up to its octopole. Assuming that the noise in the filtered maps is uncorrelated between the positions of galaxies in the survey, we derive a simple analytic form for the power spectrum covariance of the relative pairwise kSZ temperature in redshift space. While many previous studies have assumed optimistically that the optical depth of the galaxies $\tau_{\rm T}$ in the survey is known, we marginalize over $\tau_{\rm T}$, to compute constraints on the growth rate $f$ and the expansion rate $H$. For realistic sure parameters, we find that combining kSZ and galaxy redshift survey data reduces the marginalized $1$-$\sigma$ errors on $H$ and $f$ by $\sim50$-$70\%$ compared to the galaxy-only analysis.