The mass of the galactic halo derived from the luminosity function of high-velocity stars

The local luminosity function of high-velocity stars is derived on the basis of a complete sample of stars of large proper motion with trigonometric parallaxes. The fraction of these stars belonging to a roughly spherical galactic halo is deduced by using a kinematical criterion based on space velocities of metal-poor RR Lyrae variables. The local mass density of halo stars is about 1.7 x 10- solar masses per cubic parsec, corresponding to a fractional mass within the Sun's distance from the center of 6 percent, i.e., an order of magnitude lower than that of the massive halo proposed by Ostriker and Peebles. Subject headings: galactic structure - high-velocity stars - luminosity function - proper-motion stars - stellar statistics