Journal Article

Dynamics of the Magellanic Clouds in a Lambda cold dark matter universe

Michael Boylan-Kolchin, Gurtina Besla and Lars Hernquist

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 414, issue 2, pages 1560-1572
Published in print June 2011 | ISSN: 0035-8711
Published online June 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.18495.x
Dynamics of the Magellanic Clouds in a Lambda cold dark matter universe

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We examine Milky Way–Magellanic Cloud systems selected from the Millennium-II Simulation in order to place the orbits of the Magellanic Clouds in a cosmological context. Our analysis shows that satellites massive enough to be LMC analogues are typically accreted at late times. Moreover, those that are accreted at early times and survive to the present have orbital properties that are discrepant with those observed for the LMC. The high velocity of the LMC, coupled with the dearth of unbound orbits seen in the simulation, argues that the mass of the MW’s halo is unlikely to be less than 2 × 1012 M. This conclusion is further supported by statistics of haloes hosting satellites with masses, velocities and separations comparable to those of the LMC. We further show that: (1) LMC and SMC-mass objects are not particularly uncommon in MW-mass haloes; (2) the apparently high angular momentum of the LMC is not cosmologically unusual; and (3) it is rare for a MW halo to host a LMC–SMC binary system at z= 0, but high speed binary pairs accreted at late times are possible. Based on these results, we conclude that the LMC was accreted within the past four Gyr and is currently making its first pericentric passage about the MW.

Keywords: Galaxy: formation; Galaxy: fundamental parameters; galaxies: formation; galaxies: kinematics and dynamics; Magellanic Clouds

Journal Article.  9838 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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