Dark Matter Deficient Galaxies and Their Member Star Clusters Form Simultaneously during High-velocity Galaxy Collisions in 1.25 pc Resolution Simulations

Abstract

How diffuse dwarf galaxies that are deficient in dark matter—such as NGC1052-DF2 and NGC1052-DF4—formed remains a mystery. Along with their luminous member globular clusters (GCs), the so-called dark matter deficient galaxies (DMDGs) have challenged observers and theorists alike. Here we report a suite of galaxy collision simulations using the adaptive mesh refinement code Enzo with 1.25 pc resolution, which demonstrates that high-velocity galaxy collisions induce the formation of DMDGs and their star clusters (SCs) simultaneously. With a numerical resolution that is significantly better than our previous study, we resolve the dynamical structure of the produced DMDGs and the detailed formation history of their SCs, which are possible progenitors of the DMDG’s member GCs. In particular, we show that a galaxy collision with a high relative velocity of ∼300 km s −1 , invoking severe shock compression, spawns multiple massive SCs M ⋆ ≳ 10 6 M ⊙ in <150 Myr after the collision. At the end of the ∼800 Myr evolution in our fiducial run, the resulting DMDG of M ⋆ ≃ 3.5 × 10 8 M ⊙ hosts 10 luminous M V ≲ −8.5 mag, gravitationally bound SCs with a line-of-sight velocity dispersion 11.2 km s −1 . Our study suggests that DMDGs and their luminous member SCs could form simultaneously in high-velocity galaxy collisions while being in line with the key observed properties of NGC1052-DF2 and NGC1052-DF4.