Spatial distribution of Galactic Wolf–Rayet stars and implications for the global population

• Published in: Monthly notices of the Royal Astronomical Society 2015-03, Vol.447 (3), p.2322-2322
• Main Authors: Rosslowe, C K, Crowther, P A
• Format: Article
• Language: English
• Subjects: Accounting; Astrophysics; Construction; Evolutionary; Mathematical models; Milky Way; Milky Way Galaxy; Orbits; Spectroscopy; Spectrum analysis; Star & galaxy formation; Stars; Surveys
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stu2525

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 (~40 pc half-width at half-maximum) between Galactocentric radii 3.5-10 kpc, in accordance with other star formation tracers. We highlight 12 WR stars located at vertical distances of greater than or equal to 300 pc from the mid-plane. Analysis of the radial variation in WR subtypes exposes a ubiquitously higher N.../N... 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 plus or minus 250 Galactic WR stars, implying an average duration of ~ 0.4 Myr 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 K... ... 17.5 mag will be necessary to identify 95 per cent 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 A provides a complete inventory of 322 Galactic WR stars discovered since the VIIth catalogue (313 including Annex), including a revised nomenclature scheme. (ProQuest: ... denotes formulae/symbols omitted.)