Author/Authors :
Brinkmann، J. نويسنده , , Fukugita، Masataka نويسنده , , Eisenstein، Daniel J. نويسنده , , Lupton، Robert H. نويسنده , , Liebert، James نويسنده , , Munn، Jeffrey A. نويسنده , , Schneider، Donald P. نويسنده , , Winget، D. E. نويسنده , , Kleinman، S. J. نويسنده , , Knapp، G. R. نويسنده , , Nitta، Atsuko نويسنده , , Harris، Hugh C. نويسنده , , Kilic، Mukremin نويسنده , , Williams، Kurtis A. نويسنده , , Hippel، Ted von نويسنده , , Levine، Stephen E. نويسنده , , Monet، David G. نويسنده , , Metcalfe، T. S. نويسنده , , Smith، J. Allyn نويسنده ,
Abstract :
A sample of white dwarfs is selected from the Sloan Digital Sky Survey (SDSS) Data Release 3 using their reduced proper motions, based on improved proper motions from combined SDSS and USNO-B data. Numerous SDSS and follow-up spectra (Kilic and coworkers) are used to quantify completeness and contamination of the sample; kinematics models are used to understand and correct for velocity-dependent selection biases. A luminosity function is constructed covering the range 7 < Mbol < 16, and its sensitivity to various assumptions and selection limits is discussed. The white dwarf luminosity function based on 6000 stars is remarkably smooth and rises nearly monotonically to Mbol = 15.3. It then drops abruptly, although the small number of low-luminosity stars in the sample and their unknown atmospheric composition prevent quantitative conclusions about this decline. Stars are identified that may have high tangential velocities, and a preliminary luminosity function is constructed for them.
