Wolf-Rayets in IC10: Probing the Nearest Starburst

Abstract

IC10 is the nearest starburst galaxy, as revealed both by its Halpha surface brightness and the large number of Wolf-Rayet stars (WRs) per unit area. The relative number of known WC- to WN-type WRs has been thought to be unusually high (~2), unexpected for IC10's metallicity. In this Letter we report the first results of a new and deeper survey for WRs in IC10. We sucessfully detected all of the spectroscopically known WRs, and based upon comparisons with a neighboring control field, estimate that the total number of WRs in IC10 is about 100. We present spectroscopic confirmation of two of our WR candidates, both of which are of WN type. Our photometric survey predicts that the actual WC/WN ratio is ~0.3. This makes the WC/WN ratio of IC 10 consistent with that expected for its metallicity, but greatly increases the already unusually high number of WRs, resulting in a surface density that is about 20 times higher than in the LMC. If the majority of these candidates are spectroscopically confirmed, IC10 must have an exceptional population of high mass stars.