Are Disks of Satellites Comprised of Tidal Dwarf Galaxies?

Abstract

It was found that satellites of nearby galaxies can form flattened co-rotating structures called disks of satellites or planes of satellites. Their existence is not expected by the current galaxy formation simulations in the standard dark matter-based cosmology. On the contrary, modified gravity offers a promising alternative: the objects in the disks of satellites are tidal dwarf galaxies, that is, small galaxies that form from tidal tails of interacting galaxies. After introducing the topic, we review here our work on simulating the formation of the disks of satellites of the Milky Way and Andromeda galaxies. The initial conditions of the simulation were tuned to reproduce the observed positions, velocities and disk orientations of the galaxies. The simulation showed that the galaxies had a close flyby 6.8 Gyr ago. One of the tidal tails produced by the Milky Way was captured by Andromeda. It formed a cloud of particles resembling the disk of satellites at Andromeda by its size, orientation, rotation and mass. A hint of a disk of satellites was formed at the Milky Way too. In addition, the encounter induced a warp in the disk of the simulated Milky Way that resembles the real warp by its magnitude and orientation. We present here, for the first time, the proper motions of the members of the disk of satellites of Andromeda predicted by our simulation. Finally, we point out some of the remaining open questions which this hypothesis, for the formation of disks of satellites, brings up.

Dark sector domain walls could explain the observed planes of satellites

“…If several TDGs form from a single tidal tail, they would approximately share the same orbital plane and direction. This has been proffered as a potential origin for the observed planes of satellites [29,33,[64][65][66][67][68][69]. Indeed, TDGs have been observed to form in external galaxies (e.g.…”

Dark sector domain walls could explain the observed planes of satellites

“…If several TDGs form from a single tidal tail, they would approximately share the same orbital plane and direction. This has been proffered as a potential origin for the observed planes of satellites [29,33,[65][66][67][68][69][70]. Indeed, TDGs have been observed to form in external galaxies (e.g.…”

The Relevance of Dynamical Friction for the MW/LMC/SMC Triple System

“…The solutions for those satellite galaxies for which proper motions were available imply tension with the existence of DM halos since no infall solutions were found. In contrast, without the DM component, the satellite galaxies would be orbiting about the MW, having been most likely born as tidal dwarf galaxies during the MW-Andromeda encounter about 10 Gyr ago [25,26,33]. A further test for the presence of the DM component applying dynamical friction was achieved by Roshan et al [34], who found the observed bars of disk galaxies to be too long and rotating too fast in comparison with the theoretically expected bars in the presence of DM halos that absorb the bar's angular momentum.…”