Twenty‐Three High‐Redshift Supernovae from the Institute for Astronomy Deep Survey: Doubling the Supernova Sample at<i>z</i>&gt; 0.7

Abstract

We present photometric and spectroscopic observations of 23 high-redshift supernovae (SNe) spanning a range of z 0:34 1:03, nine of which are unambiguously classified as Type Ia. These SNe were discovered during the IfA Deep Survey, which began in 2001 September and observed a total of 2.5 deg 2 to a depth of approximately m % 25 26 in RIZ over 9-17 visits, typically every 1-3 weeks for nearly 5 months, with additional observations continuing until 2002 April. We give a brief description of the survey motivations, observational strategy, and reduction process. This sample of 23 high-redshift SNe includes 15 at z ! 0:7, doubling the published number of objects at these redshifts, and indicates that the evidence for acceleration of the universe is not due to a systematic effect proportional to redshift. In combination with the recent compilation of Adopting the constraint that total 1:0, we obtain best-fit values of m ; 0:33; 0:67 using 22 SNe from this survey augmented by the literature compilation. We show that using the empty-beam model for gravitational lensing does not eliminate the need for > 0. Experience from this survey indicates great potential for similar large-scale surveys while also revealing the limitations of performing surveys for z > 1 SNe from the ground.