2009ApJ...694L.136M

We present the optical and X-ray properties of four clusters recently discovered by the South Pole Telescope (SPT) using the Sunyaev-Zel'dovich effect (SZE). The four clusters are located in one of the common survey areas of the southern sky that is also being targeted by the Atacama Cosmology Telescope (ACT) and imaged by the CTIO Blanco 4 m telescope. Based on publicly available griz optical images and XMM-Newton and ROSAT X-ray observations, we analyze the physical properties of these clusters and obtain photometric redshifts, luminosities, richness, and mass estimates. Each cluster contains a central elliptical whose luminosity is consistent with SDSS cluster studies. Our mass estimates are well above the nominal detection limit of the SPT and ACT; the new SZE clusters are very likely massive systems with M ≳ 5x10¹⁴ M_☉.