Biases on the cosmological parameters and thermal SZ residuals

TL;DR

This paper analyzes how ignoring secondary anisotropies, especially residual thermal SZ signals, biases cosmological parameters in CMB data analysis, with implications for the Planck experiment.

Contribution

It derives an exact analytical formula for parameter biases caused by additive signals and applies it to assess residual thermal SZ effects on Planck data.

Findings

Neglecting residual thermal SZ signals biases n_s and tau by multiple sigma.

Biases in Omega_b are also present but smaller.

Analytical method enables precise bias estimation in CMB analyses.

Abstract

We examine the biases induced on cosmological parameters when the presence of secondary anisotropies is not taken into account in Cosmic Microwave Background analyses. We first develop an exact analytical expression for computing the biases on parameters when any additive signal is neglected in the analysis. We then apply it in the context of the forthcoming Planck experiment. For illustration, we investigate the effect of the sole residual thermal Sunyaev--Zel'dovich signal that remains after cluster extraction. We find in particular that analyses neglecting the presence of this contribution introduce on the cosmological parameters n_s and tau biases, at least 6.5 and 2.9 times their one sigma confidence intervals. The Omega_b parameter is also biased to a lesser extent.