Journal Article

Corrective effect of many-body interactions in dynamical friction

Shigeki Inoue

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 416, issue 2, pages 1181-1190
Published in print September 2011 | ISSN: 0035-8711
Published online September 2011 | e-ISSN: 1365-2966 | DOI:
Corrective effect of many-body interactions in dynamical friction

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Dynamical friction is a fundamental and important phenomenon in astrophysics. The Chandrasekhar formula is a well-known analytical estimation of the effect. However, current astrophysicists have realized that the formula is not correct in some cases because of several approximations used in the formulation and/or complex non-linearities in the real Universe. For example, it has been indicated that dynamical friction does not work in cored density profiles (constant density in the central region) despite the Chandrasekhar formula predicting drag force even for constant densities. In the first half of this paper, I show by N-body simulations that many-body interactions are also important in actual dynamical friction though derivation of the Chandrasekhar formula is based on the assumption of two-body interaction. In the simulation, the many-body interactions are caused by a very small number of field particles corotating with a perturber. However, the contribution from the many-body interactions accounts for a non-negligible fraction of the actual dynamical friction. In the second half of the paper, I discuss why the cored profiles suppress the dynamical friction. One possible explanation is that the corrective effect of the many-body interactions drives orbital motion of the perturber. The cessation of dynamical friction by this corrective effect would be feasible even in shallow cusp density profiles although the shallow cusp may evolve into a constant density.

Keywords: galaxies: dwarf; galaxies: haloes; galaxies: kinematics and dynamics; galaxies: star clusters: general

Journal Article.  7260 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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