Program: GN-2010B-Q-44

We propose MOS spectroscopic follow-up to our recent deep GMOS imaging (GN-2009B-Q-9) of the dwarf, irregular Local Group galaxy IC10, which has revealed a number of additional candidate Wolf-Rayet stars. Unique among nearby metal-poor dwarfs, IC10 possesses an unusually large carbon-sequence Wolf-Rayet population (WC subtypes) as deduced from 4m imaging surveys. However, because IC10 lies at a low Galactic latitude, and therefore suffers from large foreground dust absorption, these will be seriously incomplete. We have therefore carried out a comprehensive imaging survey of emission line sources in IC10 using new GMOS narrow-band filters. Despite synthesis models predicting that nitrogen-sequence Wolf-Rayet stars (WN subtypes) should dominate the Wolf-Rayet population at SMC-like metallicities, these stars appear to contribute only a minority of the 26 spectroscopically confirmed WR stars in IC10 (Crowther et al. 2003). A large WC/WN number ratio suggests that either IC10 experienced a global starburst ~5 Myr ago or previous imaging surveys failed to detect the majority of the WN population (Massey & Holmes 2002). MOS spectroscopy of new candidates will finally allow us to discriminate between these two possibilities. New spectroscopic datasets will also enable a calibration of intrinsic properties of individual metal-poor WR stars (Crowther & Hadfield 2006).