The first optical spectra ofWolf-Rayet stars in M101 revealed with Gemini/GMOS

Abstract

Deep narrow-band Hubble Space Telescope (HST) imaging of the iconic spiral galaxy M101 has revealed over a thousand new Wolf-Rayet (WR) candidates. We report spectrographic confirmation of 10 He II-emission line sources hosting 15WR stars.We find WR stars present at both sub- and super-solar metallicities with WC stars favouring more metal-rich regions compared to WN stars. We investigate the association of WR stars with HII regions using archival HST imaging and conclude that the majority of WR stars are in or associated with HII regions. Of the 10 emission lines sources, only one appears to be unassociated with a star-forming region. Our spectroscopic survey provides confidence that our narrow-band photometric candidates are in fact bona fide WR stars, which will allow us to characterize the progenitors of any core-collapse supernovae that erupt in the future in M101.