The Magellanic Group and the Seven Dwarfs

TL;DR

This paper proposes a theory that the Magellanic Clouds and associated dwarf galaxies entered the Milky Way as a group, explaining their distribution, dynamics, and recent discoveries of dwarf associations.

Contribution

It introduces a novel group infall model for dwarf galaxies, addressing orbital configurations, velocity distributions, and dwarf associations in the Milky Way.

Findings

Explains the planar orbital configuration of some MW dwarf spheroidals.

Provides a mechanism for the luminosity and velocity distribution of MW satellites.

Predicts most dwarfs are found in associations, supported by recent discoveries.

Abstract

The Magellanic Clouds were the largest members of a group of dwarf galaxies that entered the Milky Way (MW) halo at late times. This group, dominated by the LMC, contained ~4% of the mass of the Milky Way prior to its accretion and tidal disruption, but ~70% of the known dwarfs orbiting the MW. Our theory addresses many outstanding problems in galaxy formation associated with dwarf galaxies. First, it can explain the planar orbital configuration populated by some dSphs in the MW. Second, it provides a mechanism for lighting up a subset of dwarf galaxies to reproduce the cumulative circular velocity distribution of the satellites in the MW. Finally, our model predicts that most dwarfs will be found in association with other dwarfs. The recent discovery of Leo V (Belokurov et al. 2008), a dwarf spheroidal companion of Leo IV, and the nearby dwarf associations supports our hypothesis.