Single or binary origin of Wolf-Rayet stars? Which mode is dominant?

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Project involves exploitation of imaging and spectroscopic optical datasets obtained with the VLT (FORS) and Gemini (GMOS) to identify Wolf-Rayet stars in nearby star forming galaxies such as NGC6946. Wolf-Rayet stars are chemically evolved massive stars whose atmospheres exhibit the products of core H (He, N) and core He (C, O) burning, so arise either via powerful stellar winds from single high mass stars (> 25 Msun in Solar Neighbourhood) or mass exchange in close massive binary sysems (> 8 Msun). Single WR stars will be located within or close to young star forming regions (few Myr, with associated nebulosity) while binary WR stars may be located in significantly older (tens of Myr, lacing nebulosity). We will be able to compare the location of WR stars in face on spiral galaxies with respect to ionized regions to help address this question. Quantitative WR populations of galaxies will exploit upcoming DR2 from GAIA which will provide distances to nearby Milky Way WR stars for the first time - to date this approach has largely been limited to metal poor WR populations in the Magellanic Clouds. It is also not currently established whether Wolf-Rayet stars are the main progenitors to stripped envelope core-collapse supernovae, so comparisons between the spatial location of WR stars and stripped ccSNe will also be made.