New Estimates of the Solar-Neighborhood Massive Star Birthrate and the Galactic Supernova Rate

The birthrate of stars of masses >=10 M_solar is estimated from a sample of just over 400 O3-B2 dwarfs within 1.5 kpc of the Sun and the result extrapolated to estimate the Galactic supernova rate contributed by such stars. The solar-neighborhood Galactic-plane massive star birthrate is estimated at ~176 stars kpc^-3 Myr^-1. On the basis of a model in which the Galactic stellar density distribution comprises a ``disk+central hole'' like that of the dust infrared emission (as proposed by Drimmel and Spergel), the Galactic supernova rate is estimated at probably not less than ~1 nor more than ~2 per century and the number of O3-B2 dwarfs within the solar circle at ~200,000.