SPT-CL J0546-5345: A Massive z > 1 Galaxy Cluster Selected Via the Sunyaev-Zel'dovich Effect with the South Pole Telescope

TL;DR

This paper reports the spectroscopic confirmation of the most distant galaxy cluster discovered via the Sunyaev-Zel'dovich Effect at z > 1, demonstrating the effectiveness of SZE in identifying massive high-redshift clusters.

Contribution

It presents the first spectroscopic confirmation of a z > 1 galaxy cluster discovered through SZE, establishing a new benchmark for high-redshift cluster detection.

Findings

Cluster at z=1.067 confirmed with 21 members

Velocity dispersion of 1179 km/s indicating high mass

Estimated mass of approximately 8 x 10^{14} Msun

Abstract

We report the spectroscopic confirmation of SPT-CL J0546-5345 at <z> = 1.067. To date this is the most distant cluster to be spectroscopically confirmed from the 2008 South Pole Telescope (SPT) catalog, and indeed the first z > 1 cluster discovered by the Sunyaev-Zel'dovich Effect (SZE). We identify 21 secure spectroscopic members within 0.9 Mpc of the SPT cluster position, 18 of which are quiescent, early-type galaxies. From these quiescent galaxies we obtain a velocity dispersion of 1179^{+232}_{-167} km/s, ranking SPT-CL J0546-5345 as the most dynamically massive cluster yet discovered at z > 1. Assuming that SPT-CL J0546-5345 is virialized, this implies a dynamical mass of M_200 = 1.0^{+0.6}_{-0.4} x 10^{15} Msun, in agreement with the X-ray and SZE mass measurements. Combining masses from several independent measures leads to a best-estimate mass of M_200 = (7.95 +/- 0.92) x 10^{14} Msun. The spectroscopic confirmation of SPT-CL J0546-5345, discovered in the wide-angle, mass-selected SPT cluster survey, marks the onset of the high redshift SZE-selected galaxy cluster era.