Cold dark matter microhalo survival in the Milky Way

Journal article

Authors/Editors

Angus, Garry

Research Areas

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Publication Details

Author list: Angus GW, Zhao HS

Publisher: Oxford University Press

Place: OXFORD

Publication year: 2007

Journal: Monthly Notices of the Royal Astronomical Society (0035-8711)

Journal acronym: MON NOT R ASTRON SOC

Volume number: 375

Issue number: 4

Start page: 1146

End page: 1156

Number of pages: 11

ISSN: 0035-8711

eISSN: 1365-2966

Languages: English-Great Britain (EN-GB)

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Abstract

A special purpose N-body simulation has been built to understand the tidal heating of the smallest dark matter substructures (10(-6) M. and 0.01 pc) from the grainy potential of the Milky Way due to individual stars in the disc and the bulge. To test the method, we first run simulations of single encounters of microhaloes with an isolated star, and compare with analytical predictions of the dark particle bound fraction as a function of impact parameter. We then follow the orbits of a set of microhaloes in a realistic flattened Milky Way potential. We concentrate on (detectable) microhaloes passing near the Sun with a range of pericentre and apocentre. Stellar perturbers near the orbital path of a microhalo would exert stochastic impulses, which we apply in a Monte Carlo fashion according to the Besancon model for the distribution of stars of different masses and ages in our Galaxy. Also incorporated are the usual pericentre tidal heating and disc shocking. We give a detailed diagnosis of typical microhaloes and find microhaloes with internal tangential anisotropy are slightly more robust than the ones with radial anisotropy. In addition, the dark particles generally go through of a random walk in velocity space and diffuse out of the microhaloes. We show that the typical destruction time-scales are strongly correlated with the stellar density averaged along a microhalo's orbit over the age of the stellar disc. We also present the morphology of a microhalo at several epochs which may hold the key to dark matter detections. We checked our results against different choices of microhalo mass, virial radius and anisotropy.

Keywords

Dark matter, Galaxy : kinematics and dynamics

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