Energy transfer between dark matter and gas during collisions

Abstract

Using the simulation code GIZMO, two different configurations of dark matter and gas were collided at three different resolutions in order to study the energy transfer between the dark matter and gas. The first configuration is of two dark matter halos offset from a central gas distribution. Energy was transferred from the dark matter into the gas, and an increase in the gas temperature and kinetic energy occurred. The second configuration is of two mixed gas and dark matter halos offset from each other. This collision sees a spike in temperature initially, and then an adiabatic expansion and cooling that leaves the gas cooler then it was initially, while also seeing an increase in kinetic energy. When normalized by taking the energy values as a ratio of the initial total energy, the energy transfer from the dark matter to the gas ended up being roughly the same value ( 0.025) for the two collisions, at the highest resolutions.