Ironing out primordial temperature fluctuations with polarisation: optimal detection of cosmic structure imprints

TL;DR

This paper introduces a method leveraging CMB polarisation data to improve the detection of primordial temperature fluctuations and the integrated Sachs-Wolfe effect, significantly enhancing signal-to-noise ratios.

Contribution

It presents a novel approach that uses CMB polarisation to reduce primordial fluctuation noise in cross-correlation studies, improving ISW detection sensitivity.

Findings

Achieves a signal-to-noise ratio of up to 8.5 for ISW detection.

Enhances SNR by 23% over standard methods with perfect data.

Improves detection sensitivity by 16% compared to previous methods.

Abstract

Secondary anisotropies of the cosmic microwave background (CMB) can be detected by using the cross-correlation between the large-scale structure (LSS) and the CMB temperature fluctuations. In such studies, chance correlations of primordial CMB fluctuations with the LSS are the main source of uncertainty. We present a method for reducing this noise by exploiting information contained in the polarisation of CMB photons. The method is described in general terms and then applied to our recently proposed optimal method for measuring the integrated Sachs-Wolfe (ISW) effect. We obtain an expected signal-to-noise ratio of up to 8.5. This corresponds to an enhancement of the signal-to-noise by 23 per cent as compared to the standard method for ISW detection, and by 16 per cent w.r.t. our recently proposed method, both for the best-case scenario of having perfect (noiseless) CMB and LSS data.