Dark Matter Deficient Galaxies Produced Via High-velocity Galaxy Collisions In High-resolution Numerical Simulations

TL;DR

This study uses high-resolution simulations to explore whether high-velocity galaxy collisions can produce dark matter deficient galaxies, finding that such collisions can separate dark matter from gas and potentially form DMDGs, but resolution is critical.

Contribution

The paper demonstrates that high-velocity galaxy collisions can produce dark matter deficient galaxies in simulations, highlighting the importance of resolution for this formation pathway.

Findings

DMDGs can form from high-velocity galaxy collisions separating dark matter from gas.

Simulations show shock and tidal interactions compress gas to form stars in DMDGs.

No DMDGs formed in the IllustrisTNG simulation due to resolution limits.

Abstract

The recent discovery of diffuse dwarf galaxies that are deficient in dark matter appears to challenge the current paradigm of structure formation in our Universe. We describe the numerical experiments to determine if the so-called dark matter deficient galaxies (DMDGs) could be produced when two gas-rich, dwarf-sized galaxies collide with a high relative velocity of $\sim 300\,{\rm kms^{-1}}$. Using idealized high-resolution simulations with both mesh-based and particle-based gravito-hydrodynamics codes, we find that DMDGs can form as high-velocity galaxy collisions separate dark matter from the warm disk gas which subsequently is compressed by shock and tidal interaction to form stars. Then using a large simulated universe IllustrisTNG, we discover a number of high-velocity galaxy collision events in which DMDGs are expected to form. However, we did not find evidence that these types of collisions actually produced DMDGs in the TNG100-1 run. We argue that the resolution of the numerical experiment is critical to realize the "collision-induced" DMDG formation scenario. Our results demonstrate one of many routes in which galaxies could form with unconventional dark matter fractions.