Complete sample of white dwarfs, hot subdwarfs, and quasars

An analysis is made of a complete sample of hot white dwarfs, identified spectroscopically from candidates selected for ultraviolet excess without regard to proper motion. The luminosity function and local space density of hot white dwarfs are derived, giving 1.43 +- .28 per 1000 cubic parsecs for M/sub v/ < 12.75. A model of the local rate of star formation is constructed, which, when combined with white dwarf cooling theory, satisfactorily reproduces the observed luminosity function. The predicted densities at fainter absolute magnitudes also agree with the observations although uncertainties in the data do not allow a determination of the change in star formation rate with time. The model predicts a range of scale heights for hot white dwarfs of 220 to 270 pc, and a total local density of degenerate stars of at least 20 per 1000 cubic parsecs. The assumption of a single population of DA white dwarfs with identical composition is not adequate to explain the observed color--color diagram