Clumps and streams in the local dark matter distribution

In cold dark matter cosmological models, structures form and grow through the merging of smaller units. Numerical simulations have shown that such merging is incomplete; the inner cores of haloes survive and orbit as 'subhaloes' within their hosts. Here we report a simulation that resolves...

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Bibliographic Details
Published in:Nature 2008-08, Vol.454 (7205), p.735-738
Main Authors: Diemand, J, Kuhlen, M, Madau, P, Zemp, M, Moore, B, Potter, D, Stadel, J
Format: Article
Language:English
Subjects:
Astronomy
Cosmic rays
Cosmology
Dark matter
Dark matter (Astronomy)
Dark matter (stellar, interstellar, galactic, and cosmological)
Earth, ocean, space
Exact sciences and technology
Fundamental astronomy and astrophysics. Instrumentation, techniques, and astronomical observations
Gravity effects
Humanities and Social Sciences
letter
Milky Way
multidisciplinary
Science
Science & Technology - Other Topics
Stars & galaxies
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Summary:In cold dark matter cosmological models, structures form and grow through the merging of smaller units. Numerical simulations have shown that such merging is incomplete; the inner cores of haloes survive and orbit as 'subhaloes' within their hosts. Here we report a simulation that resolves such substructure even in the very inner regions of the Galactic halo. We find hundreds of very concentrated dark matter clumps surviving near the solar circle, as well as numerous cold streams. The simulation also reveals the fractal nature of dark matter clustering: isolated haloes and subhaloes contain the same relative amount of substructure and both have cusped inner density profiles. The inner mass and phase-space densities of subhaloes match those of recently discovered faint, dark-matter-dominated dwarf satellite galaxies, and the overall amount of substructure can explain the anomalous flux ratios seen in strong gravitational lenses. Subhaloes boost -ray production from dark matter annihilation by factors of 4 to 15 relative to smooth galactic models. Local cosmic ray production is also enhanced, typically by a factor of 1.4 but by a factor of more than 10 in one per cent of locations lying sufficiently close to a large subhalo. (These estimates assume that the gravitational effects of baryons on dark matter substructure are small.)
ISSN:0028-0836
1476-4687
1476-4679
DOI:10.1038/nature07153