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White Dwarfs: Contributors and Tracers of the Galactic Dark-Matter Halo

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.


Item Type:Book Section
Related URLs:
URLURL TypeDescription
https://doi.org/10.1142/9789812778017_0024DOIArticle
https://arxiv.org/abs/astro-ph/0106392arXivDiscussion Paper
ORCID:
AuthorORCID
Koopmans, L. V. E.0000-0003-1840-0312
Blandford, R. D.0000-0002-1854-5506
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
Funders:
Funding AgencyGrant Number
NSFAST-9900866
NASAGO-06543.03-95A
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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