IC-10 - A POOR COUSIN RICH IN WOLF-RAYET STARS

We have obtained narrow-band CCD imaging of the Local Group galaxy IC 10 in order to identify and characterize the Wolf-Rayet star population. We have found sixteen "high significance" Wolf-Rayet candidates and obtained verification spectra of four of them. We infer a WC/WN ratio of almost-equal-to O.5 and a surface density of Wolf-Rayet stars in IC 10 considerably larger than in NGC 6822, a galaxy well matched in morphology and composition; the inferred formation rate for massive stars in IC 10 is as high as any other galaxy in the Local Group. This conflicts with the recent comparison by Hodge and Lee of the luminosity functions of the H II regions of these two galaxies. We suggest that the explanation for this conflict is partially due to the absence of gas (H I holes) in IC 10, possibly produced by the influence of massive stars on their environment. We speculate that the distance of IC 10 is about 1.5 Mpc, and that the reddening is somewhat smaller [E(B - V) almost-equal-to 0. 5] than that normally adopted in studies of this galaxy.