Self-consistent determinations of the total amount of matter near the sun

Abstract

The combined Poisson-Boltzmann equation for the gravitational potential is solved numerically for detailed Galaxy models whose mass components have been determined previously by a variety of observational techniques. The basic assumption made is that the disk is composed of a finite number of isothermal components. The calculated potential as a function of height above the plane is used to fit the distribution of F stars reported by Hill, Hilditch, and Barnes to a distance of 200 pc. The inferred mass and column densities depend upon the model adopted for the unseen matter. The total mass density at the solar position is 0.185 + or - 0.02 solar mass per cu pc if the distribution of unobserved matter is proportional to the distribution of observed material, the Bahcall and Soneira Galaxy model is adopted, and the isothermal approximation is valid. The corresponding column density is 67 solar mass per sq pc, and the disk mass-to-light ratio is 2.9. The total mass and column densities are computed for a number of other assumptions about the unobserved material and the Galaxy model. The inferred mass and column densities are not sensitive to small contaminations or departures from isothermality in the sample of F stars that was used. The unobservd disk material is at least as large as 50 percent of the total observed disk material in all of the models considered.