The White Dwarf Luminosity Function from Sloan Digital Sky Survey Imaging Data
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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 Msub-bol 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 Msub-bol 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.