Program: GS-2008B-Q-45

We propose to obtain new Gemini/GMOS images and spectra of three extremely bright Type II SNe (2007it, 2007oc, 2007od) as part of a unique detailed study of dust formation of SNe at visible, near- and mid-IR wavelengths. These new observations will be combined with already approved 2008A Gemini/GMOS (band 1) and Spitzer Cycle 5 (priority 1) programs as well as a proposed joint HST-NOAO program for 2009. Because all three 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. The spectra and images of 2007oc and 2007od will be obtained three times in 2008B at approximately 60-day intervals covering the span of ~300 to 480 days since the explosion, while 2007it will be sampled once at the start of the semester (330 days) and once at the end (500 days). 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. The unusual brightness of these SNe and the sensitivity of Gemini/GMOS will allow us to follow their evolution at regular intervals for up to 700 days. 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.