Scaleheights of Low Mass Stars from the Luminosity Function of the Local White Dwarfs

Abstract

It is shown that a combination of the observed luminosity function of the local white dwarfs and the theoretical cooling rates of a typical white dwarf suggests an approximately constant rate of formation of the white dwarfs. This rate is found to be about a factor of three lower than the observed birthrate of their immediate progenitors. This discrepancy is here interpreted as a three-fold increase in the scaleheight of the white dwarfs due to dynamical interaction with stars, molecular clouds; an average white dwarf being much more aged than an average progenitor. Since the low mass stars on an average are even slightly more long-lived than these white dwarfs, one can place a lower bound on the scaleheights of the low mass stars to be given by the required scaleheights of the white dwarfs, which is, according to the present work, 660 pc in the solar neighbourhood.