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Description
We present a ground-based, near-infrared search for lensed supernovae behind the massive cluster Abell 1689 at z=0.18, which is one of the most powerful gravitational telescopes that nature provides. Our survey was based on multi-epoch J-band observations with the HAWK-I instrument on VLT, with supporting optical data from the Nordic Optical Telescope. Our search resulted in the discovery of five photometrically classified, core-collapse supernovae with high redshifts of 0.671<z<1.703 and magnifications in the range {DELTA}m=-0.31 to -1.58mag, as calculated from lensing models in the literature. Owing to the power of the lensing cluster, the survey had the sensitivity to detect supernovae up to very high redshifts, z~3, albeit for a limited region of space. We present a study of the core-collapse supernova rates for 0.4<=z<2.9, and find good agreement with previous estimates and predictions from star formation history. During our survey, we also discovered two Type Ia supernovae in A 1689 cluster members, which allowed us to determine the cluster Ia rate to be 0.14+0.19-0.09+/-0.01SNuB*h^2^ (SNuB=10^-12^SNeL_{sun},B_^-1^yr^-1^), where the error bars indicate 1{sigma} confidence intervals, statistical and systematic, respectively. The cluster rate normalized by the stellar mass is 0.10+0.13-0.096+/-0.02 in SNuM*h^2^ (SNuM=10^-12^SNeM_{sun}_^-1^yr^-1^). Furthermore, we explore the optimal future survey for improving the core-collapse supernova rate measurements at z>~2 using gravitational telescopes, and for detections with multiply lensed images, and we find that the planned WFIRST space mission has excellent prospects.
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