Tidal Dwarf Galaxies and missing baryons
  Tidal dwarf galaxies form during the interaction, collision or merger of
massive spiral galaxies. They can resemble "normal" dwarf galaxies in terms of
mass, size, and become dwarf satellites orbiting around their massive
progenitor. They nevertheless keep some signatures from their origin, making
them interesting targets for cosmological studies. In particular, they should
be free from dark matter from a spheroidal halo. Flat rotation curves and high
dynamical masses may then indicate the presence of an unseen component, and
constrain the properties of the "missing baryons", known to exist but not
directly observed. The number of dwarf galaxies in the Universe is another
cosmological problem that can be significantly impacted if tidal dwarf galaxies
formed frequently at high redshift, when the merger rate was high, and many of
them survived until today.
