Mon. Not. R. Astron. Soc., 447, 2322-2347 (2015/March-1)
Spatial distribution of Galactic Wolf-Rayet stars and implications for the global population.
ROSSLOWE C.K. and CROWTHER P.A.
Abstract (from CDS):
We construct revised near-infrared absolute magnitude calibrations for 126 Galactic Wolf-Rayet (WR) stars at known distances, based in part upon recent large-scale spectroscopic surveys. Application to 246 WR stars located in the field permits us to map their Galactic distribution. As anticipated, WR stars generally lie in the thin disc ( ∼ 40pc half-width at half-maximum) between Galactocentric radii 3.5-10kpc, in accordance with other star formation tracers. We highlight 12 WR stars located at vertical distances of ≥ 300pc from the mid-plane. Analysis of the radial variation in WR subtypes exposes a ubiquitously higher NWC/NWN ratio than predicted by stellar evolutionary models accounting for stellar rotation. Models for non-rotating stars or accounting for close binary evolution are more consistent with observations. We consolidate information acquired about the known WR content of the Milky Way to build a simple model of the complete population. We derive observable quantities over a range of wavelengths, allowing us to estimate a total number of 1900±250 Galactic WR stars, implying an average duration of ∼ 0.4Myr for the WR phase at the current Milky Way star formation rate. Of relevance to future spectroscopic surveys, we use this model WR population to predict follow-up spectroscopy to KS ≃ 17.5 mag will be necessary to identify 95 percent of Galactic WR stars. We anticipate that ESA's Gaia mission will make few additional WR star discoveries via low-resolution spectroscopy, though will significantly refine existing distance determinations. Appendix provides a complete inventory of 322 Galactic WR stars discovered since the VIIth catalogue (313 including Annex), including a revised nomenclature scheme.