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.
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