Distribution of effective temperatures as a function of the white dwarf object number (left axis). The observational values of Goldsbury et al. (2012) are displayed in the gray shaded area, while the results of our Monte Carlo simulations are shown with red lines. The blue dashed lines show the cooling sequence for M_WD = 0.53 M_⊙ of Renedo et al. (2010) for Z = 0.001 under different assumptions. The correction factor of the observed sample of white dwarfs is also displayed (right axis). See the online edition of the journal for a color version of this plot.