Mass calibration of distant SPT galaxy clusters through expanded weak lensing follow-up observations with HST, VLT & Gemini-South

TL;DR

This study presents weak lensing mass measurements for 30 distant galaxy clusters from the SPT-SZ survey, refining mass estimates and the SZ-mass scaling relation, highlighting discrepancies with Planck cosmology.

Contribution

It provides expanded weak lensing measurements for high-redshift clusters, improved calibration methods, and refined constraints on the SZ-mass scaling relation including its redshift evolution.

Findings

Mass scale lower by ~24% compared to Planck cosmology

Refined SZ-mass scaling relation with redshift dependence

Need for larger weak lensing samples to test cosmological models

Abstract

Expanding from previous work we present weak lensing measurements for a total sample of 30 distant ($z_\mathrm{median}=0.93$) massive galaxy clusters from the South Pole Telescope Sunyaev-Zel'dovich (SPT-SZ) Survey, measuring galaxy shapes in Hubble Space Telescope (HST) Advanced Camera for Surveys images. We remove cluster members and preferentially select $z\gtrsim 1.4$ background galaxies via $V-I$ colour, employing deep photometry from VLT/FORS2 and Gemini-South/GMOS. We apply revised calibrations for the weak lensing shape measurements and the source redshift distribution to estimate the cluster masses. In combination with earlier Magellan/Megacam results for lower-redshifts clusters we infer refined constraints on the scaling relation between the SZ detection significance and the cluster mass, in particular regarding its redshift evolution. The mass scale inferred from the weak lensing data is lower by a factor $0.76^{+0.10}_{-0.14}$ (at our pivot redshift $z=0.6$) compared to what would be needed to reconcile a flat Planck $\nu\Lambda$CDM cosmology (in which the sum of the neutrino masses is a free parameter) with the observed SPT-SZ cluster counts. In order to sensitively test the level of (dis-)agreement between SPT clusters and Planck, further expanded weak lensing follow-up samples are needed.