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(-0.4)(+0.6) x 10(15) M(circle dot), 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) M(circle dot). 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.