Annu. Rev. Astron. Astrophys. 2000. 38: 667-715 Copyright © 2000 by Annual Reviews. All rights reserved

3.1. Supernova events

An estimate of the SN rate at high redshift can provide important constraints on the star-formation history of galaxies and on models for SN progenitors [Pain et al. 1996, Madau et al. 1998, Ruiz-Lapuente & Canal 1998]. [Gilliland & Phillips 1998] took second-epoch WFPC2 observations of the HDF-N field in December 1997 and reported two SN detections, at I = 26.0 and 27.0. [Mannucci & Ferrara 1999] report a very faint detection, at I = 28.5 of an object that brightened by 1 mag in 5 days in the original HDF-N images. The number of SNe expected in a single epoch of HDF-N observations is 0.5-1 [Gilliland et al. 1999], consistent with the number of detections. The advanced camera for surveys (ACS) will provide substantial benefits for future SN searches, because it will have roughly twice the solid angle at five times the sensitivity of WFPC2. Based on the HDF numbers, a survey of 12 ACS fields to HDF I-band depth should identify roughly 25 SNe, and would cost ~ 100 orbits.