A population model of the solar neighbourhood thin disc white dwarfs

Abstract

A B S T R A C T We present a model of the solar neighbourhood (d 6300 K. After determination of the bias owing to a residual incompleteness with cool WDs, we find a corrected value of R6300 of 0.68 (‐0.24). This is in good agreement with our WD population model: its temperature distribution yields R 6300 = 0.77. For a spherical volume around the Sun, with d < 100 pc, our population model suggests a total of about 13 700 WDs (omiting part of the WDs with a binary system origin, an estimated 7 ‐ 2 per cent of the total count). A subsample, limited to magnitude 19.0 (as expected for the European Space Agency mission Gaia), would contain about 7750 WDs of this population model. With a less deep magnitude limit of B = 16.0, more typical of current observed WD samples (SN Ia Progenitor surveY; SPY), the number of objects is reduced to only 1350. We use this specific synthetic subsample to test the completeness of the prospective SPY WD sample, which (with over 50 per cent of the candidates now observed) is already the largest sample of WDs with high-resolution spectra. We find that within d < 100 pc and for B < 16.0 SPY will deliver a fairly complete (almost 80 per cent) sample.