The Progenitors of Subluminous Type I[CLC]a[/CLC] Supernovae

We find that spectroscopically peculiar subluminous SNe Ia come from an oldpopulation. Of the sixteen subluminous SNe Ia known, ten are found in E/S0galaxies, and the remainder are found in early-type spirals. The probabilitythat this is a chance occurrence is only 0.2%. The finding that subluminous SNeIa are associated with an older stellar population indicates that for asufficiently large lookback time (already accessible in current high redshiftsearches) they will not be found. Due to a scarcity in old populations,hydrogen and helium main sequence stars and He red giant stars that undergoRoche lobe overflow are unlikely to be the progenitors of subluminous SNe Ia.Earlier findings that overluminous SNe Ia (dM15(B) < 0.95) come from a youngprogenitor population are confirmed. The fact that subluminous SNe Ia andoverluminous SNe Ia come from different progenitor populations and also havedifferent properties is a prediction of the CO white dwarf merger progenitorscenario.Comment: 7 pages, 1 figure, Accepted to ApJ Letter