Zooming in on a Simulated Milky Way-Sagittarius Analog Collision

Dwarf galaxies – low-mass galaxies distinct from star clusters by the presence of a dark matter halo – are some of the most intriguing objects in our universe. Interactions between larger host galaxies such as our Milky Way and their dwarf galaxy satellites are thought to play a key role in the evolution of the satellites – affecting everything from stellar structure to star formation. However, simulations of these collisions have thus far been either too low in resolution to study the impact on the dwarf in sufficient detail, or have been idealized – lacking the important effects of large-scale structure possible only in a cosmological simulation. By performing particle-splitting on a FIRE (Feedback In Realistic Environments) cosmological zoom-in simulation of a Milky Way-Sagittarius analog collision, we can achieve higher resolution locally around the collision site, and study in more detail than ever before what effects mergers like these might have on the dwarf galaxy and its own “ultra-faint” satellite galaxies. This project involves developing a particle counting algorithm that determines how many star, gas, and dark matter particles from the host galaxy come within a certain radius of the satellite. We present the number of interacting particles for various threshold radii in a FIRE dwarf-dwarf merger simulation as a test case for our particle counting algorithm, as well as initial results for a Milky Way-Sagittarius analog merger. Future work will include determining how far we can feasibly increase the collision-site resolution, and identifying the appropriate simulation parameters to run the simulation with particle-splitting.