Collision-induced formation of dark-matter-deficient galaxies

The standard galaxy formation model predicts that galaxies form within a Cold Dark Matter (CDM) halo and that galaxies are dominated by dark matter. However, recent observations have discovered dark-matter-deficient galaxies with much less dark matter mass than theoretical predictions, and the process of their formation has been discussed. Here, we investigate the physical processes of galaxy formation by collisions between gas-rich dark matter subhalos within the context of the CDM paradigm. We investigate the formation process of dark-matter-deficient galaxies by running three-dimensional simulations of the collision process between dark matter subhalos (DMSHs) with the same mass of 109M⊙ colliding the velocity of 100 km s−1. We then compared the effect of different supernova feedback models, the subgrid physics of the simulation, on the collision-induced formation of galaxies. The results show that the strong feedback model ejects gas out of the system more efficiently than the weak feedback model, leading to lower star formation rates and the formation of a more extended galaxy. Finally, dark-matter-deficient galaxies with stellar masses of ∼ 107M⊙ and ∼ 108M⊙ are formed in the weak and strong feedback models, respectively.