THE TYPE IA SUPERNOVA RATE AT Z-SIMILAR-TO-0.4

We present the first measurement of the rate of Type Ia supernovae at high redshift. The result is derived by using a large subset of data f rom the Supernova Cosmology Project. Three supernovae were discovered in a surveyed area of 1.7 deg(2). The survey spanned a similar to 3 we ek baseline and used images with 3 sigma limiting magnitudes of R simi lar to 23. We present our methods for estimating the numbers of galaxi es and the number of solar luminosities to which the survey is sensiti ve, as well as the supernova detection efficiency, which is used to de termine the control time, the effective time for which the survey is s ensitive to a Type Ia event. We derive a rest-frame Type Ia supernova detection efficiency, which is used to determine the control time, the effective time for which the survey is sensitive to a Type Ia event. We derive a rest-frame Type Ia supernova (SN) rate at z similar to 0.4 of 0.82(-0.37-0.25)(+0.54+0.37) h(2) SNu (1 SNu = 1 SN per century pe r 10(10)L(B).), where the first uncertainty is statistical and the sec ond includes systematic effects. For the purposes of observers, we als o determine the rate of SNe, per sky area surveyed, to be 4.4(-16.2)(23.9) SNe yr(-1) deg(-2) for SN magnitudes in the range 21.3 < R < 22. 3.