Stars of low luminosity

The mass density of stars in the Solar Neighbourhood is a fundamental parameter in' Galactic Structure studies. We have applied the method of photometric parallaxes (the M , (V-I)) relation ) to two complete samples of late-type dwarfs; one selected from an objective prism survey, the other from COSMOS photographic photometry of BVI UK Schmidt Telescope plates. The resultant kinematically unbiased luminosity function shows that the stellar number density peaks at M^ = +13 locally, falling off very steeply thereafter. This result excludes hydrogen burning stars brighter than M^ = +19 as significant contributors to any local missing mass. We have also examined the kinematic selection effects inherent in proper-motion based determinatio-ns of the luminosity function, and show that high velocity halo stars significantly affect results derived by this method. These effects are substantial enough to permit an investigation of the local subdwarf number density, which we find to be """CI. 4 percent that of disk dwarfs. Finally, using UBVRIJHK photometry, we have applied a blackbody fitting technique to derive temperatures and luminosities for low luminosity dwarfs, and conclude that even the least luminous are consistent with their interpretation as main sequence dwarfs