Leo IV & V - A possible dwarf galaxy pair ?
  The last few years have seen the discovery of many faint and ultra-faint
dwarf spheroidal galaxies around the Milky Way. Among these is a pair of
satellites called Leo IV and Leo V. This pair is found at large distances from
the Milky Way (154 and 175 kpc respectively). The rather small difference in
radial distance, and the fact that they also show a close projected distance on
the sky, has led to the idea that we might be seeing a new pair of bound
galaxies - like the Magellanic Clouds. In this paper we investigate this
speculation by means of a simple integration code (confirming the results with
full N-body simulations). As the luminous mass of both faint dwarfs is far too
low to allow them to be bound, we simulate the pair assuming extended dark
matter haloes. Our results show that the minimum dark matter mass required for
the pair to be bound is rather high - ranging from 1.6 x 10^10 Msun to 5.4 x
10^10 Msun (within the virial radii). Computing the mass of dark matter within
a commonly adopted radius of 300 pc shows that our models are well within the
predicted range of dark matter content for satellites so faint. We therefore
conclude that it could be possible that the two galaxies constitute a bound
pair.
