The Spatial Distribution of O–B5 Stars in the Solar Neighborhood as Measured by [ITAL]HIPPARCOS[/ITAL][ITAL]Hipparcos[/ITAL]

Abstract

We have developed a method to calculate the fundamental parameters of the vertical structure of the Galaxy in the solar neighborhood from trigonometric parallaxes alone. The method takes into account Lutz-Kelker-type biases in a self-consistent way and has been applied to a sample of O-B5 stars obtained from the Hipparcos catalog. We find that the Sun is located 24.2+/-1.7 (random)+/-0.4 (systematic) pc above the Galactic plane and that the disk O-B5 stellar population is distributed with a scale height of 34.2+/-0.8 (random)+/-2.5 (systematic) pc and an integrated surface density of [1.62+/-0.04 (random)+/-0.14 (systematic)]×10-3 stars pc-2. A halo component is also detected in the distribution and constitutes at least ~5% of the total O-B5 population. The O-B5 stellar population within ~100 pc of the Sun has an anomalous spatial distribution, with a less than average number density. This local disturbance is probably associated with the expansion of the Gould Belt. Based on data from the Hipparcos astrometry satellite.