Twenty‐Three High‐Redshift Supernovae from the Institute for Astronomy Deep Survey: Doubling the Supernova Sample atz> 0.7

We present photometric and spectroscopic observations of 23 high redshiftsupernovae spanning a range of z=0.34-1.03, 9 of which are unambiguouslyclassified as Type Ia. These supernovae were discovered during the IfA DeepSurvey, which began in September 2001 and observed a total of 2.5 squaredegrees to a depth of approximately m=25-26 in RIZ over 9-17 visits, typicallyevery 1-3 weeks for nearly 5 months, with additional observations continuinguntil April 2002. We give a brief description of the survey motivations,observational strategy, and reduction process. This sample of 23 high-redshiftsupernovae includes 15 at z>0.7, doubling the published number of objects atthese redshifts, and indicates that the evidence for acceleration of theuniverse is not due to a systematic effect proportional to redshift. Incombination with the recent compilation of Tonry et al. (2003), we calculatecosmological parameter density contours which are consistent with the flatuniverse indicated by the CMB (Spergel et al. 2003). Adopting the constraintthat Omega_total = 1.0, we obtain best-fit values of (Omega_m,Omega_Lambda)=(0.33, 0.67) using 22 SNe from this survey augmented by theliterature compilation. We show that using the empty-beam model forgravitational lensing does not eliminate the need for Omega_Lambda > 0.Experience from this survey indicates great potential for similar large-scalesurveys while also revealing the limitations of performing surveys for z>1 SNefrom the ground.Comment: 67 pages, 12 figures, 12 tables, accepted for publication in the Astrophysical Journa