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