Relativistic and wide-angle corrections to galaxy power spectra

TL;DR

This paper investigates relativistic and wide-angle effects on galaxy power spectra, demonstrating that combining galaxy populations enhances detection of these signals, with significance levels up to over 15 sigma in future surveys.

Contribution

It provides a comprehensive analysis of relativistic and wide-angle corrections, including their combined effects and detection prospects in upcoming galaxy surveys.

Findings

Relativistic and wide-angle effects can be detected with high significance in future surveys.

Combining two galaxy populations suppresses cosmic variance, improving signal detectability.

Detection significance varies from 5σ to over 15σ depending on line-of-sight configurations.

Abstract

Galaxy surveys contain information on the largest scales via wide-angle and relativistic contributions. By combining two different galaxy populations, we can suppress the strong cosmic variance on ultra-large scales and thus enhance the detectability of the signals. The relativistic Doppler and Sachs-Wolfe effects are of a similar magnitude to the leading wide-angle corrections, so that it is important to treat them together, especially since they can partially cancel. The power spectra depend on the choice of line of sight for each galaxy pair and we present results for a general line of sight. Then we estimate the detection significance of the auto- and cross-power spectra for a variety of cases. We use two futuristic galaxy samples based on a `beyond-DESI' survey and a SKA Phase 2 survey, covering 15,000\,deg$^2$ up to $z=1$. We find a detection significance for the total relativistic wide-angle effects that ranges from $\sim 5\sigma$ to $>15\sigma$, depending on the line-of-sight configuration.