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

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 M200 = 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 M200 = (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.