Searching for the lost Unicorn: a prominent feature in the radial
  velocity distribution of stars in Vela from Gaia DR2 data
  Stellar streams are ubiquitous in the Galactic halo and they can be used to
improve our understanding of the formation and evolution of the Milky Way as a
whole. The so-called Monoceros Ring might have been the result of satellite
accretion. Guglielmo et al. have used N-body simulations to search for the
progenitor of this structure. Their analysis shows that, if the Ring has a
dwarf galaxy progenitor, it might be found in the background of one out of
eight specific areas in the sky. Here, we use Gaia DR2 data to perform a
systematic exploration aimed at confirming or rejecting this remarkable
prediction. Focusing on the values of the radial velocity to uncover possible
multimodal spreads, we identify a bimodal Gaussian distribution towards
Galactic coordinates (l, b) = (271, +2) degrees in Vela, which is one of the
locations of the progenitor proposed by Guglielmo et al. This prominent feature
with central values 60+/-7 km/s and 97+/-10 km/s, may signal the presence of
the long sought progenitor of the Monoceros Ring, but the data might also be
compatible with the existence of an unrelated, previously unknown,
kinematically coherent structure.
