Program: GS-2008A-DD-2

We have been awarded Priority 1 Cycle 5 time with Spitzer/IRAC to observe three extremely bright Type II SNe ( 2007oc, 2007od, 2007it) as part of a unique detailed study of dust formation of SNe at visible, near- and mid-IR wavelengths. We have proposed to observe all three in 2008B with Gemini/GMOS but we are monitoring only SN 2007it in 2008A because the other two were not discovered until after the deadline. Therefore, we are asking for Director's Time to obtain one set of spectra and images with GMOS for SN 2007oc and 2007od in the period May 15 - June 15. The observations proposed here, together with our proposed observations for 2008B, will bracket the time period during the summer when we expect to obtain our first epoch of Spitzer imaging. Most importantly, the likely time of dust formation begins ~300 days after the SN explosion so the proposed 2008B observations may be obtained after dust formation has already begun. Therefore, these Director's Time observations are vital to our program because they will provide a pre-dust formation template against which to compare our planned observations later in 2008 and in 2009. We have also proposed for HST Cycle 17 imaging of these SNe. Because these SNe are so unusually bright (V ~ 13.5 mag), we should be able to follow their evolution for at least two years (2007-2009). This is very important because dust typically condenses in the SN ejecta approximately 300-600 days after the initial explosion. We have previously shown using Gemini and Spitzer that monitoring the evolution of H-alpha and [O I] emission-line profiles, g'r'i photometry, and IR emission in Type II SNe are very sensitive techniques for detecting new dust forming in the ejecta. We hope that the unique combination of Gemini, Spitzer and HST data all obtained during the dust forming period will answer the perplexing questions concerning when and how much dust is produced by Type II SNe. Using our radiative transfer codes, these observations will allow us to investigate the clumpiness of dust in the ejecta and better estimate the total mass of dust. The results will have important implications for the evolution of dust-rich galaxies at high redshift (z~6) where young high-mass stars may be significant dust producers.