Measuring Redshift-Space Distortions using Photometric Surveys

TL;DR

This paper demonstrates how redshift-space distortions can be measured using photometric surveys' angular correlation functions, enabling tests of cosmological models and photometric redshift accuracy.

Contribution

It introduces a method to measure RSD from photometric survey data and assesses its accuracy with simulations, advancing cosmological analysis techniques.

Findings

Dark Energy Survey can measure fσ8 with 17% accuracy in a narrow redshift slice.

Extending measurements over multiple bins can determine the growth index γ with 25% accuracy.

Analytic predictions are validated using mock catalogs from simulations.

Abstract

We outline how redshift-space distortions (RSD) can be measured from the angular correlation function w({\theta}), of galaxies selected from photometric surveys. The natural degeneracy between RSD and galaxy bias can be minimized by comparing results from bins with top-hat galaxy selection in redshift, and bins based on the radial position of galaxy pair centres. This comparison can also be used to test the accuracy of the photometric redshifts. The presence of RSD will be clearly detectable with the next generation of photometric redshift surveys. We show that the Dark Energy Survey (DES) will be able to measure f(z){\sigma}_8(z) to a 1{\sigma} accuracy of (17 {\times} b)%, using galaxies drawn from a single narrow redshift slice centered at z = 1. Here b is the linear bias, and f is the logarithmic rate of change of the linear growth rate with respect to the scale factor. Extending to measurements of w({\theta}) for a series of bins of width 0.02(1 + z) over 0.5 < z < 1.4 will measure {\gamma} to a 1{\sigma} accuracy of 25%, given the model f = {\Omega}_m(z)^{\gamma}, and assuming a linear bias model that evolves such that b = 0.5 + z (and fixing other cosmological parameters). The accuracy of our analytic predictions is confirmed using mock catalogs drawn from simulations conducted by the MICE collaboration.