Halo white dwarf luminosity function for our fiducial Galactic model. The top panel shows the theoretical white dwarf luminosity function obtained when the cooling sequences incorporating residual hydrogen burning are employed (open circles). We also show, with solid squares, the observed halo luminosity function of Rowell & Hambly (2011). The bottom panel shows the residuals between the observed luminosity function and the theoretical calculations, Δ = 2(N_obs − N_sim) / (N_obs + N_sim).