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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 709823.0, MPI für Astronomie / Publikationen_mpia
A thousand shadows of Andromeda: Rotating planes of satellites in the Millennium-II cosmological Simulation
Authors:Ibata, R. A.; Ibata, N. G.; Lewis, G. F.; Martin, N. F.; Conn, A.; Elahi, P.; Arias, V.; Fernando, N.
Date of Publication (YYYY-MM-DD):2014
Title of Journal:The Astrophysical Journal Letters
Issue / Number:1
Start Page:id. L6 (5 pp)
Audience:Not Specified
Abstract / Description:In a recent contribution, Bahl & Baumgardt investigated the incidence of planar alignments of satellite galaxies in the Millennium-II simulation and concluded that vast, thin planes of dwarf galaxies, similar to that observed in the Andromeda galaxy (M31), occur frequently by chance in Lambda-cold dark matter cosmology. However, their analysis did not capture the essential fact that the observed alignment is simultaneously radially extended, yet thin, and kinematically unusual. With the caveat that the Millennium-II simulation may not have sufficient mass resolution to identify confidently simulacra of low-luminosity dwarf galaxies, we re-examine that simulation for planar structures, using the same method as employed by Ibata et al. on the real M31 satellites. We find that 0.04% of host galaxies display satellite alignments that are at least as extreme as the observations, when we consider their extent, thickness, and number of members rotating in the same sense. We further investigate the angular momentum properties of the co-planar satellites, and find that the median of the specific angular momentum derived from the line-of-sight velocities in the real M31 structure (1.3 × 104 km s-1 kpc) is very high compared to systems drawn from the simulations. This analysis confirms that it is highly unlikely that the observed structure around the Andromeda galaxy is due to a chance occurrence. Interestingly, the few extreme systems that are similar to M31 arise from the accretion of a massive sub-halo with its own spatially concentrated entourage of orphan satellites.
Free Keywords:dark matter; galaxies: halos; galaxies: individual: M31
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:ISSN:0004-637X %R 10.1088/2041-8205/784/1/L6
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