29.01.2019 15:15

Modified Gravity in Plane Sight

Indranil Banik, St. Andrews / Bonn


The satellite galaxies of the Milky Way and Andromeda mostly lie within thin planes. This strongly suggests a violent formation mechanism whereby galactic interactions(s) formed tidal tails from the outer disks of these galaxies. These tidal features could later coalesce into the observed satellite planes, a process known to occur and feasible in the ΛCDM standard cosmological paradigm (Newtonian gravity + dark matter). However, it implies that the satellites should be free of dark matter and thus have very low internal velocity dispersions, contrary to observations.

Thus, I will present a reasonable model for the satellite galaxies using an empirical acceleration-based modification to gravity. This theory (MOND) can explain internal dynamics of galaxies without dark matter and in fact with very little freedom. In MOND, the Milky Way and Andromeda flew past each other ~9 Gyr ago, with most of their satellites forming from tidal debris during this interaction. In recently published restricted N-body simulations of this flyby (MNRAS, 477,4768), it is possible to reproduce the large-scale geometry of both satellite planes as wll as the age and thickness of the Milky Ways's thick disk, an old structure which formed rapidly with an associated starburst around the expected time of the interaction. Some models can also get counter-rotating satellites around the Milky Way (analogues to Sculptor) but not around Andromenda, where there is no evidence for counter-rotators. I will finish with future work in this area and other possible test of MOND.

Kategorie: HISKP News, Kolloquium, News