The Distribution of Low-Mass Stars in the Galactic Disc

The complex interdependence of stellar binarity, the stellar mass-luminosity relation, the mass function, the color-magnitude relation, and Galactic disk structure is quantified. A mass-M(V) relation and a model for the change of stellar luminosity with changes in chemical abundance and age are derived. A combination of this with detailed modeling of all astrophysical and observational contributions to the Malmquist scatter makes it possible to model star-count data without approximating Malmquist corrections. It is shown that a single mass function and normalization explain the stellar distribution towards both Galactic poles, as well as the distribution of stars within a distance of 5.2 pc of the sun.