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On the Shape of the Galactic Dark Matter Halo

Published online by Cambridge University Press:  05 March 2013

Amina Helmi
Amina Helmi*
Affiliation:
Astronomical Institute Utrecht, 3508 TA Utrecht, The Netherlands Kapteyn Institute, 9700 AV Groningen, The Netherlands
*
3E-mail: [email protected]
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Abstract

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The confined nature of the debris from the Sagittarius dwarf to a narrow trail on the sky has recently prompted the suggestion that the dark matter halo of our Galaxy should be nearly spherical (Ibata et al. 2001; Majewski et al. 2003). This would seem to be in strong contrast with predictions from cold dark matter (CDM) simulations, where dark halos are found to have typical density axis ratios of 0.6 to 0.8. Here I present numerical simulations of the evolution of a system like the Sagittarius dSph in a set of Galactic potentials with varying degrees of flattening. These simulations show that the Sagittarius streams discovered so far are too young dynamically to be sensitive to the shape of the dark halo of the Milky Way. The data presently available are entirely consistent with a Galactic dark matter halo that could either be oblate or prolate, with density axis ratios c/a that range from 0.6 to 1.6 within the region of the halo probed by the orbit of the Sagittarius dwarf.

Keywords

dark mattergalaxies: halos, shapesGalaxy: halo, dynamics, structure
Type
Research Article
Information
Publications of the Astronomical Society of Australia , Volume 21 , Issue 2: The Fifth Workshop on Galactic Chemodynamics , 2004 , pp. 212 - 215
Copyright
Copyright © Astronomical Society of Australia 2004

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