Selection of High-z Supernovae Candidates

Deep, ground based, optical wide-field supernova searches are capable of detecting a large number of supernovae over a broad redshift range up to z ∼ 1.5. While it is practically unfeasible to obtain spectroscopic redshifts of all the supernova candidates right after the discovery, we show that the magnitudes and colors of the host galaxies, as well as the supernovae, can be used to select high-z supernova candidates, for subsequent spectroscopic and photometric follow-up. Using Monte-Carlo simulations we construct criteria for selecting galaxies in well-defined redshift bands. For example, with a selection criteria using B − R and R−I colors we are able to pick out potential host galaxies for which z ≥ 0.85 with 80% confidence level and with a selection efficiency of 64–86%. The method was successfully tested using real observations from the HDF. Similarly, we show that that the magnitude and colors of the supernova discovery data can be used to constrain the redshift. With a set of cuts based on V − R and R− I in a search to mI ∼ 25, supernovae at z ∼ 1 can be selected in a redshift interval σz ≤ 0.15. Subject headings: Cosmology: observations—supernovae: general