Relatively Dark Matter: The Local Mass Density of Stellar Remnants

Extract

The Palomar-Green Survey produced statistically complete samples of hot white dwarfs and subdwarfs, from which the local mass density of these objects can be determined. The luminosity function of hot hydrogen-atmosphere white dwarfs (DA's) was recently re-determined by Fleming, Liebert, and Green (1985, Ap. J., submitted). The contribution of each of the 353 objects to the local space density was calculated from the ensemble of limiting magnitudes and a spectroscopically or photometrically derived absolute magnitude. The local surface density of white dwarfs with M_V < 12.75 (log L/L⊙ > −3.1; T_E > 9000 K) is 0.32 ± 0.03 pc⁻². Assuming an exponential disk with scale height 250 pc, we derive the differential luminosity function in the figure; the total volume density is 0.65 ± 0.06 per 1000 pc³. He atmosphere degenerates add another 20%.