The mass and luminosity functions and the formation rate of DA white dwarfs in the Sloan Digital Sky Survey^*

¹ Yuanpei Program, Peking University, Beijing, 100871, PR China
² School of Physics, Peking University, Beijing, 100871, PR China
³ Department of Astronomy, Peking University, Beijing, 100871, PR China e-mail: wuxb@bac.pku.edu.cn

Received: 26 August 2006
Accepted: 5 January 2007

Abstract

Aims.The SDSS Data Release 1 includes 1833 DA white dwarfs (WDs) and forms the largest homogeneous sample of WDs. This sample provides the best opportunity to study the statistical properties of WDs.

Methods.We adopt a recently established theoretical model to calculate the mass and distance of each WD using the observational data. Then we adopt a bin-correction method to correct for selection effects and use the weight-factor method to calculate the luminosity function, the continuous mass function and the formation rate of these WDs.

Results.The SDSS DA WD sample is incomplete and suffers seriously from selection effects. After corrections for the selection effects, only 531 WDs remain. From this final sample we derive the most up-to-date luminosity function and mass function, in which we find a broad peak of WD masses centered around 0.58 . The DA WD space density is calculated as 8.8110^-5 pc^-3 and the formation rate is 2.57910^-13 pc^-3 yr^-1.

Conclusions.The statistical properties of the SDSS DA WD sample are generally in good agreement with previous observational and theoretical studies, and provide us information on the formation and evolution of WDs. However, a larger and more complete all-sky WD sample is still needed to explain some subtle disagreements and unresolved issues.