J. Tumlinson, C. Thom, J. Werk, J. Prochaska, T. Tripp, D. Weinberg, M. Peeples, J. O'Meara, B. Oppenheimer, J. Meiring and 4 other author(s). (2011)cite arxiv:1111.3980Comment: This paper is part of a set of three papers on circumgalactic gas observed with the Cosmic Origins Spectrograph on HST, to be published in Science, together with related papers by Tripp et al. and Lehner & Howk, in the November 18, 2011 edition. This version has not undergone final copyediting. Please see Science online for the final printed version.