We present photometric and spectroscopic observations of 23 high redshift supernovae spanning a range of z = 0.34 - 1.03 , 9 of which are unambiguously classified as Type Ia .
These supernovae were discovered during the IfA Deep Survey , which began in September 2001 and observed a total of 2.5 square degrees to a depth of approximately m \approx 25 - 26 in RIZ over 9-17 visits , typically every 1-3 weeks for nearly 5 months , with additional observations continuing until April 2002 .
We give a brief description of the survey motivations , observational strategy , and reduction process .
This sample of 23 high-redshift supernovae includes 15 at z \geq 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 Tonry et al .
( 2003 ) , we calculate cosmological parameter density contours which are consistent with the flat universe indicated by the CMB ( Spergel et al .
2003 ) .
Adopting the constraint that \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 the literature compilation .
We show that using the empty-beam model for gravitational lensing does not eliminate the need for \Omega _ { \Lambda } > 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 .