The first optical spectra of Wolf–Rayet stars in M101 revealed with Gemini/GMOS

Abstract

Deep narrow-band 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 iiemission line sources hosting 15 WR stars. We find WR stars present at both sub-and supersolar metalicities with WC stars favouring more metal-rich regions compared to WN stars. We investigate the association of WR stars with H ii regions using archival HST imaging and conclude that the majority of WR stars are in or associated with H ii 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 bonafide WR stars, which will allow us to characterise the progenitors of any core-collapse supernovae that erupt in the future in M101.

The Wolf–Rayet Content of the Galaxies of the Local Group and Beyond

“…Other surveys have been carried out for WR stars in even more distant systems with the 8-m VLT by Lucy Hadfield, Joanne Bibby and Crowther: IC 4662 (2.3 Mpc) [106], NGC 7793 (3.4 Mpc) [107], NGC 1313 (4.1 Mpc) [108], M83 (4.5 Mpc) [109], NGC 5068 (5-7 Mpc) [110], NGC 6744 (7-11 Mpc) [111]. Most interesting, perhaps, has been their HST study of M101, a large spiral located at a (relatively speaking) modest 6.7 Mpc distance [112,113], with followup spectroscopy with the Gemini 8-m [114]. To these we note the more recent study of the WR content of NGC 625 (3.9 Mpc) [115] by integral field spectroscopy on the VLT by Ana Monreal-Ibero and collaborators.…”