Southern cosmology survey. I. optical cluster detections and predictions for the southern common-area millimeter-wave experiments

We present first results from the Southern Cosmology Survey, a new multiwavelength survey of the southern sky coordinated with the Atacama Cosmology Telescope (ACT), a recently commissioned ground-based millimeter (mm)-band cosmic microwave background (CMB) experiment. This article presents full analysis of archival optical multiband imaging data covering an 8deg ² region near right ascension 23 hr and declination -55°, obtained by the Blanco 4 m telescope and Mosaic-II camera in late 2005. We describe the pipeline we have developed to process this large data volume, obtain accurate photometric redshifts, and detect optical clusters. Our cluster finding process uses the combination of a matched spatial filter, photometric redshift probability distributions, and richness estimation. We present photometric redshifts, richness estimates, luminosities, and masses for eight new optically selected clusters with mass greater than 3 × 10¹⁴ M at redshifts out to 0.7. We also present estimates for the expected Sunyaev-Zel'dovich effect (SZE) signal from these clusters as specific predictions for upcoming observations by ACT, the South Pole Telescope and Atacama Pathfinder Experiment.