THE DISTRIBUTION OF INTERSTELLAR DUST IN THE SOLAR NEIGHBORHOOD

We surveyed the IRAS data base at the positions of the 1808 O6-B9.5 stars in The Bright Star Catalog for extended objects with excess emission at 60 mum, indicating the presence of interstellar dust at the location of the star. Within 400 pc the filling factor of the interstellar medium for dust clouds with a density >0.5 cm-3 is 14.6 +/- 2.4%. Above a density of 1.0 cm-3, the density distribution function appears to follow a power law of index -1.25. When the dust clouds are mapped onto the galactic plane, the sun appears to be located in a low-density region of the interstellar medium of width about 60 pc extending at least 500 pc in the direction of longitudes 80-degrees-260-degrees, a feature we call the ''local trough.''