Improving cosmological constraints from galaxy cluster number counts with CMB-cluster-lensing data: Results from the SPT-SZ survey and forecasts for the future

TL;DR

This paper demonstrates how incorporating CMB-cluster lensing data enhances cosmological constraints from galaxy cluster surveys, notably improving measurements of parameters like sigma_8 and the dark energy equation of state, with forecasts for future surveys.

Contribution

It introduces the use of CMB-cluster lensing measurements to improve cosmological parameter constraints from galaxy cluster data, including forecasts for future surveys.

Findings

Adding CMB-cluster lensing reduces uncertainty in sigma_8 by factors of 2.4 to 3.6.

Combining cluster data with Planck measurements yields sigma_8(Ω_m/0.3)^0.5 = 0.831 ± 0.020.

Future CMB-cluster lensing data can improve constraints on dark energy parameter w by 1.3 times.

Abstract

We show the improvement to cosmological constraints from galaxy cluster surveys with the addition of CMB-cluster lensing data. We explore the cosmological implications of adding mass information from the 3.1$\sigma$ detection of gravitational lensing of the cosmic microwave background (CMB) by galaxy clusters to the Sunyaev-Zel'dovich (SZ) selected galaxy cluster sample from the 2500 deg$^2$ SPT-SZ survey and targeted optical and X-ray followup data. In the $\Lambda$CDM model, the combination of the cluster sample with the Planck power spectrum measurements prefers $\sigma_8 \left(\Omega_m/0.3 \right)^{0.5} = 0.831 \pm 0.020$. Adding the cluster data reduces the uncertainty on this quantity by a factor of 1.4, which is unchanged whether or not the 3.1$\sigma$ CMB-cluster lensing measurement is included. We then forecast the impact of CMB-cluster lensing measurements with future cluster catalogs. Adding CMB-cluster lensing measurements to the SZ cluster catalog of the on-going SPT-3G survey is expected to improve the expected constraint on the dark energy equation of state $w$ by a factor of 1.3 to $\sigma(w) = 0.19$. We find the largest improvements from CMB-cluster lensing measurements to be for $\sigma_8$, where adding CMB-cluster lensing data to the cluster number counts reduces the expected uncertainty on $\sigma_8$ by factors of 2.4 and 3.6 for SPT-3G and CMB-S4 respectively.