Program: GS-2009A-Q-20

We propose GMOS-S spectroscopy of candidate Wolf-Rayet sources identified in recent VLT images of face-on, star forming spiral galaxies NGC5068 (SBd) and NGC6744 (SABbc). Red supergiants and WR stars are believed to be the immediate progenitors of Type II and Type Ib/c SNe, respectively, yet no progenitors of Type Ib/c SN have been established to date. Distinguishing between massive WR stars - possessing strong emission-line signatures - and lower mass stars in close binaries as progenitors of future Type Ib/c SN is the primary motivation behind this proposal. Specifically, high S/N spectroscopy is required to (i) confirm WR candidate regions and diagnose their stellar content, (ii) verify their super-solar metallicity through standard nebular techniques. Together with GMOS-N spectroscopy of M74 from semester 2008B plus previous VLT spectroscopy, these observations will also enable comparisons of massive stellar populations with evolutionary synthesis predictions for various metallicities.