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Title: The luminosity function for white dwarfs in the SuperCOSMOS Sky Survey
Author: Rowell, Nicholas
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2010
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I present a magnitude and proper motion limited catalogue of ~ 10,000 white dwarf candidates, obtained from the SuperCOSMOS Sky Survey by means of reduced proper motion selection. This catalogue extends to R ~ 19.75 and μ ~ 0".05 yr⁻¹, and covers more than three quarters of the sky. Spectroscopic follow-up observations have been obtained for a subsample of objects, and are used to assess the reliability of the selection procedure and contamination of the final catalogue. Photometric parallaxes provide distance estimates accurate to ~ 50%. This catalogue is used to measure the luminosity function (LF) for white dwarfs in the Solar neighbourhood over the range 4 ≤ Mbol ≤ 18. A new technique is devised to separate the LFs for disk and spheroid stars, which allows all stars to contribute to the LF even at tangential velocities where the populations overlap. The disk LF shows a sharp decline at Mbol = 15.75, in agreement with other studies, and extends over a magnitude fainter than previously determined. The spheroid LF has a sharp peak at Mbol = 15.75, then levels out and shows no sign of a drop off at faint magnitudes, as expected for a considerably older population. By simulating white dwarf LFs for stellar populations with a range of star formation histories, I measure the age of the local disk and spheroid. The disk age of 9.13⁺⁰ ⁶⁶₋₀.₆₇ Gyr agrees with that measured in similar studies, and with the basic picture of galaxy formation in a cosmological context. No reliable solution is found for the spheroid age. By integrating the LFs, I investigate the local mass density of spheroid white dwarfs, with particular reference to their contribution to the baryonic dark matter content of the Galaxy. I also place an upper limit on their contribution to the possible MACHO population and the microlensing events observed towards the LMC.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available