Testing Dark Matter Clustering with Redshift Space Distortions

TL;DR

This paper investigates how redshift space distortions in galaxy surveys can be used to measure dark matter clustering strength, providing analytic tools and forecasting current and future constraints.

Contribution

It offers a simple, accurate analytic prescription for interpreting growth rate measurements and forecasts the potential constraints on dark matter clustering from upcoming surveys.

Findings

Current data constrains dark matter clustering to 99% of standard

Future surveys could constrain clustering to 28% when marginalizing over parameters

Holding dark energy parameters fixed improves constraints to 4%

Abstract

The growth rate of large scale structure can probe whether dark matter clusters at gravitational strength or deviates from this, e.g. due to self interactions. Measurement of the growth rate through redshift space distortions in galaxy redshift surveys constrains the clustering strength, and its redshift dependence. We compare such effects on growth to those from high redshift deviations (e.g. early dark energy) or modified gravity, and give a simple, highly accurate analytic prescription. Current observations can constrain the dark matter clustering strength to F_{cl}=0.99\pm0.02 of standard, if all other parameters are held fixed, but substantial covariances exist. Future galaxy redshift surveys may constrain an evolving clustering strength to 28%, marginalizing over the other parameters, or 4% if the dark energy parameters are held fixed while fitting for dark matter growth. Tighter constraints on the nature of dark matter could be obtained by combining cosmological and astrophysical probes.