The distribution of massive stars in the Galaxy. I - The Wolf-Rayet stars

Using spectroscopic parallax, the heliocentric and Galactocentric distances of nearly all of the 157 known Wolf-Rayet stars in the Galaxy were determined. Their distribution both within and perpendicular to the Galactic plane was investigated. The overall distribution within the plane reveals spiral features which are in accord with other determinations of Galactic structure. In addition, it was found that the Galactocentric location of Wolf-Rayet stars is dependent on Wolf-Rayet subtype, with late WC stars strongly confined to regions within the solar circle. However, there is only a marginal variation in the WC/WN number ratio with distance from the Galactic center. The distribution of Wolf-Rayet stars in the direction perpendicular to the plane reveals that these objects are closely confined to, but distributed asymmetrically about, the Galactic plane; the verical scale height of the distribution is about 45 pc. It is found that the sun is located about 15 pc above the plane defined by these extreme Population I objects.