| The South Pole Telescope team has recently reported the first 21 galaxy clusters uniformly selected by a blind Sunyaev-Zel'dovich (SZ) survey. Prompt optical imaging has confirmed the existence of red-sequence galaxy overdensities at the SZ locations, and provided first estimates of their redshift and optical richness. We have also followed up a subset spectroscopically. These are some of the most massive clusters in the universe, spanning redshifts from z=0.15 to z>1, with median of 0.74. This remarkable sample serves as proof of concept for SZ cluster surveys, which will provide a new, powerful window on the nature of dark energy. We are attacking the problem of following up many hundreds or thousands of SZ detections in the coming years by developing a real-time photometric calibration tool called Stellar Locus Regression. We also attack it from a hardware standpoint by building PISCO, a simultaneous multiband CCD imager. Optimizing the observing strategy alone using SLR provides a factor of 2 in cluster-confirmation yield over standard methods, and PISCO gives another factor of 3 to 4 for z<1 clusters. Finally, we provide the first sky background characterization in the new CCD y band at Cerro Tololo in Chile, which will be used in next-generation astronomical camera systems and will provide useful additional information. as well as new challenges, for cluster studies such as this. |
