Koopmans, L. V. E. and Blandford, R. D. (2002) White Dwarfs: Contributors and Tracers of the Galactic Dark-Matter Halo. In: The Shapes of Galaxies and Their Dark Halos. World Scientific , River Edge, NJ, pp. 150-153. ISBN 978-981-02-4848-2. https://resolver.caltech.edu/CaltechAUTHORS:20190524-123210936
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Abstract
We examine the claim by Oppenheimer et al. (2001) that the local halo density of white dwarfs is an order of magnitude higher than previously thought. As it stands, the observational data support the presence of a kinematically distinct population of halo white dwarfs at the >99% confidence level. A maximum-likelihood analysis gives a radial velocity dispersion of σ h/U = 150^(+80)_(-40) km s^(-1) and an asymmetric drift of v h/α = 176^(+102)_(-80) km s^(-1), for a Schwarzschild velocity distribution function with σU:σV:σW = 1:2/3:1/2. Halo white dwarfs have a local number density of 1.1^(+2.1)_(-0.7) x 10^(-4) pc^(-3), which amounts to 0.8^(+1.6)_(-0.5) per cent of the nominal local dark-matter halo density and is 5.0^(+9.5)_(-3.2) times (90% C.L.) higher and thus only marginally in agreement with previous estimates. We discuss several direct consequences of this white-dwarf population (e.g. microlensing) and postulate a potential mechanism to eject young white dwarfs from the disc to the halo, through the orbital instabilities in triple or multiple stellar systems.
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| Additional Information: | © 2002 World Scientific Publishing Co. We thank Ben Oppenheimer for valuable discussions and sending their tabulated results. We thank David Graff and Andy Gould for pointing out an error in the normalisation of our likelihood function. LVEK thanks Priya Natarajan for organising a productive and well-organised meeting. This research has been supported by NSF AST–9900866 and STScI GO–06543.03–95A. | |||||||||
| Group: | TAPIR | |||||||||
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| Record Number: | CaltechAUTHORS:20190524-123210936 | |||||||||
| Persistent URL: | https://resolver.caltech.edu/CaltechAUTHORS:20190524-123210936 | |||||||||
| Official Citation: | White Dwarfs: Contributors and Tracers of the Galactic Dark-Matter Halo. L. V. E. Koopmans and R. D. Blandford. The Shapes of Galaxies and Their Dark Halos. March 2002, 150-153; doi: 10.1142/9789812778017_0024 | |||||||||
| Usage Policy: | No commercial reproduction, distribution, display or performance rights in this work are provided. | |||||||||
| ID Code: | 95788 | |||||||||
| Collection: | CaltechAUTHORS | |||||||||
| Deposited By: | Tony Diaz | |||||||||
| Deposited On: | 24 May 2019 20:06 | |||||||||
| Last Modified: | 03 Oct 2019 21:16 |
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