SPT-CL J0546-5345: A MASSIVEz>1 GALAXY CLUSTER SELECTED VIA THE SUNYAEV-ZEL'DOVICH EFFECT WITH THE SOUTH POLE TELESCOPE

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^–1, 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 × 10¹⁵ M _☉, 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) × 10¹⁴ M _☉. 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.