Dark Matter Deficient Galaxies and Their Member Star Clusters Form Simultaneously during High-velocity Galaxy Collisions

The discovery of diffuse dwarf galaxies that are deficient in dark matter challenged the conventional structure formation theory in the Lambda-Cold Dark Matter cosmology (van Dokkum et al. 2018, 2019). The so-called dark matter deficient galaxies (DMDGs) also exhibit abnormally luminous member globular clusters. To address the formation of the DMDGs within the current cosmological paradigm, a high-velocity collision of dwarf galaxies, a "mini-Bullet Cluster-like" event, was suggested as a mechanism that separates collisionless dark matter and stars from the interstellar gas along with severe shock compression (Silk 2019). In this work, we present a suite of idealized high-resolution galaxy collision simulations using a hydrodynamical N-body code, which demonstrates that high-velocity galaxy collisions with a relative velocity of ∼300 km/s induce the formation of multiple DMDGs and their massive member star clusters simultaneously along the trail of the colliding galaxies. The produced DMDGs and star clusters reproduce some properties from the observation while making some predictions as well. In particular, the comparison to the observation may hint at a novel method of constraining dark matter self-scattering cross section in the collision velocity scale of ~100 km/s.