Implications of bias evolution on measurements of the integrated Sachs-Wolfe effect: errors and biases in parameter estimation

TL;DR

This paper quantifies how uncertainties and evolution in galaxy bias affect the measurement of the integrated Sachs-Wolfe effect and the estimation of cosmological parameters, highlighting potential biases and degeneracies.

Contribution

It introduces a Fisher-matrix analysis to assess the impact of bias evolution on cosmological parameter estimation from iSW measurements, considering realistic bias models.

Findings

Bias evolution causes significant shifts in parameter estimates.

Ignoring bias evolution leads to underestimating errors.

Bias evolution affects large-scale iSW spectrum measurements.

Abstract

The subject of this paper is a quantification of the impact of uncertainties in bias and bias evolution on the interpretation of measurements of the integrated Sachs-Wolfe effect, in particular on the estimation of cosmological parameters. We carry out a Fisher-matrix analysis for quantifying the degeneracies between the parameters of a dark energy cosmology and bias evolution, for the combination of the PLANCK microwave sky survey with the EUCLID main galaxy sample, where bias evolution b(a)=b_0+(1-a)b_a is modelled with two parameters b_0 and b_a. Using a realistic bias model introduces a characteristic suppression of the iSW-spectrum on large angular scales, due to the altered distance-weighting functions. The errors in estimating cosmological parameters if the data with evolving bias is interpreted in the framework of cosmologies with constant bias is quantified in an extended Fisher-formalism. We find that the best-fit values of all parameters are shifted by an amount comparable to the statistical accuracy: The estimation bias in units of the statistical accuracy amounts to 1.19 for Omega_m, 0.27 for sigma_8, and 0.72 for w for bias evolution with b_a=1. Leaving b_a open as a free parameter deteriorates the statistical accuracy, in particular on Omega_m and w.