We report the spectroscopic confirmation of SPT-CL J0546-5345 at \left < z \right > = 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 _ { \mbox { \scriptsize 200 } } = 1.0 ^ { +0.6 } _ { -0.4 } \times 10 ^ { 15 } M _ { \odot } , in agreement with the X-ray and SZE mass measurements .
Combining masses from several independent measures leads to a best-estimate mass of M _ { \mbox { \scriptsize 200 } } = ( 7.95 \pm 0.92 ) \times 10 ^ { 14 } M _ { \odot } .
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 .