The Distribution of Wolf-Rayet Stars in the Galaxy

Abstract

The distances of galactic Wolf-Rayet stars are derived and their distribution on the galactic plane is shown. It is found that the various subclasses show differing degrees of concentration towards the galactic centre. All we 9 stars appear to be located within 7 kpc of the galactic centre; WN 6 and WC 7 stars show a concentration to the area within 9 kpc of the galactic centre; other subclasses are concentrated to the area outside 9 kpc of the galactic centre. Since the three subclasses that show concentration to the area within 9 kpc of the galactic centre are missing from, or rare in, the Large Magellanic Cloud we conclude that the stellar population in the Large Magellanic Cloud is very similar to that in the solar neighbourhood but quite unlike that in the inner regions of the Galaxy. Previous rate of star formation is suggested to be the controlling factor. The overall pattern of the Wolf-Rayet distribution suggests spiral arms with inclinations of 3–5°, in qualitative agreement with the theory of a spiral pattern arising from density waves suggested by Lin & Shu (1964, 1966, 1967) and Lin (1967a, b). The Wolf-Rayet stars are strongly concentrated to the inner edges of the H I and OB spiral features in Cygnus and Carina. Consistency with the density wave model is possible if star formation occurs mainly on the inner edges of spiral arms and if the Wolf-Rayet stars are exceedingly young objects.