Tidal origin of dark-matter free dwarf galaxies in the NGC 1052 group

Abstract

Discovery of dark-matter (DM) free dwarf galaxies in the NGC 1052 neighborhood has had a considerable impact on modern cosmology. They have been explained through a dwarf--dwarf head-on collision that is a rare event. We find that they could alternatively be associated with a head-on, 1:1 merger after it has been tuned to generate the E4 morphology of NGC 1052. Our simulations show that such mergers produce long-lived tidal features, associated with the remnant galaxy, and in the form of large tidal tails including tidal dwarf galaxies (TDGs). We underline that such tidal features are predicted by the hierarchical scenario in which massive galaxies are formed by galaxy mergers. The latter can reproduce both the tidal features in the NGC1052 outskirts and the observed dwarf galaxies. The simulated TDGs have similar sizes to those observed, while they are ten times smaller in the dwarf bullet scenario. However, we cannot reproduce the luminous globular cluster systems due to resolution limitations. Resolving the radial distance between the DM-free dwarfs is necessary to identify the scenario of their formation. We suggest that there should be many other examples of DM-free dwarf galaxies in the neighborhood of local massive galaxies and galaxy groups.