Local Group timing in Milgromian dynamics

Context. Local Group (LG) timing is one of the first historical probes of the so-called missing mass problem. Whilst modern cosmological probes indicate that pure baryonic dynamics is not sufficient on the largest scales, nearby galaxies and small galaxy groups persistently obey Milgrom’s MOND law,...

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Bibliographic Details
Published in:Astronomy and astrophysics (Berlin) 2013-09, Vol.557
Main Authors: Zhao, H., Famaey, B., Lüghausen, F., Kroupa, P.
Format: Article
Language:English
Subjects:
Astrophysics
galaxies: groups: individual: Local Group
Galaxy: evolution
gravitation
Sciences of the Universe
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Summary:Context. Local Group (LG) timing is one of the first historical probes of the so-called missing mass problem. Whilst modern cosmological probes indicate that pure baryonic dynamics is not sufficient on the largest scales, nearby galaxies and small galaxy groups persistently obey Milgrom’s MOND law, which implies that dynamics at small scales is possibly entirely predicted by the baryons. Aims. Here, we investigate LG timing in this context of Milgromian dynamics. Methods. We used the latest measured proper motions and radial velocities for Andromeda and the Magellanic clouds, and we integrated their orbits backwards by making use of the Milgromian two-body equation of motion. Results. With the currently measured proper motions and radial velocity of M31, we find that MOND would imply that the Milky Way (MW) and M31 first moved apart via Hubble expansion after birth, but then necessarily were attracted again by the Milgromian gravitational attraction, and had a past fly-by encounter before coming to their present positions. This encounter would most probably have happened 7 to 11 Gyr ago (0.8 
ISSN:0004-6361
1432-0746
1432-0746
DOI:10.1051/0004-6361/201321879