Constraints on the dark matter equation of state with redshift-space distortion

TL;DR

This study constrains the dark matter equation of state using redshift-space distortion data combined with other cosmic observations, finding a value close to zero but with mild preference for nonzero values, and comparing it to the standard Lambda-CDM model.

Contribution

It introduces a model with nonzero dark matter equation of state and constrains it using multiple cosmological datasets, including redshift-space distortion data.

Findings

Dark matter equation of state parameter w_dm is close to zero.

Adding fσ8(z) data tightens constraints.

No significant deviation from Lambda-CDM in 1σ region.

Abstract

In this paper, we study a model which is composed by the cosmological constant and dark matter with nonzero equation of state parameter, which could be called as $\Lambda$wDM. In the synchronous gauge, we obtain the perturbation equations of dark matter, and deduce the evolution equations of growth factor about the dark matter and baryons. Based on the Markov Chain Monte Carlo method, we constrain this model by the recently available cosmic observations which include cosmic microwave background radiation, baryon acoustic oscillation, type Ia supernovae, and $f\sigma_8(z)$ data points from redshift-space distortion. The results present a tighter constraint on the model than the case without $f\sigma_8(z)$ data. In 3$\sigma$ regions, we find the dark matter equation of state parameter $w_{dm}$=$0.000111_{- 0.000701-0.00137-0.00180}^{+0.000688+0.00136+0.00181}$. After an extra model parameter $w_{dm}$ is considered, the difference between the minimum values of $\chi^2$ of our model and standard model is $\Delta\chi^2_{min}=0.598$. Although the currently available cosmic observations mildly favor the nonzero dark matter equation of state parameter, no significant deviation from the $\Lambda$CDM model is found in 1$\sigma$ region.