The space distribution of DA white dwarfs

We present a determination of the scaleheight and luminosity function of DA white dwarfs based on a new sample of 41 faint (B < 20.9 mag) white dwarfs, spectroscopically identified as part of the AAT faint QSO survey. Maximum likelihood techniques were used to obtain a value for the scaleheight of $${z}_{0} = 275 \pm50 \text{pc}$$. Assuming such a scaleheight, the local luminosity function, $$\Phi({M}_{V})$$, derived for the AAT sample shows good agreement with that obtained previously for the Palomar Green DA white dwarf sample, particularly in the overall normalization of the luminosity function. We derive a value for the local space density of DA white dwarfs with $${M}_{V}\,\lt\,12.75$$ mag equal to $$0.60\,\pm\,0.09 \,\text{per} \,1000 \,\text{pc}^{3}$$. The combined luminosity function for both samples may be parameterized by a two power-law funcion: $$\Phi(M_V)\propto[10^{{-1.1}{(M_V-M^\ast_V)}}]+10^{{0.1}(M_V-M^\ast_V)}]^{-1}$$ where $$M_{V}^{\ast} = 11.09\,\pm\, 0.20 \,\text{mag}.$$.