Unravelling the interplay between SIDM and baryons in MW haloes: defining where baryons dictate heat transfer

We present a new set of cosmological zoom-in simulations of a Milky Way (MW)-like galaxy that for the first time include elastic velocity-dependent self-interacting dark matter (SIDM) and IllustrisTNG physics. With these simulations, we investigate the interaction between SIDM and baryons and its effects on the galaxy evolution process. We also introduce a novel set of modified dark matter-only simulations that can reasonably replicate the effects of fully realized hydrodynamics on the DM halo while simplifying the analysis and lowering the computational cost. We find that baryons change the thermal structure of the central region of the halo to a greater extent than the SIDM scatterings for MW-like galaxies. Additionally, we find that the new thermal structure of the MW-like halo causes SIDM to create cuspier central densities rather than cores because the SIDM scatterings remove the thermal support by transferring heat away from the centre of the galaxy. We find that this effect, caused by baryon contraction, begins to affect galaxies with a stellar mass of 10(8) M-circle dot and increases in strength to the MW-mass scale.

Automated summary

We use cosmological zoom-in simulations to study the interaction between self-interacting dark matter (SIDM) and baryons, and its effects on the evolution of Milky Way-like galaxies. We also propose modified dark matter-only simulations that can approximate the effects of hydrodynamics on the dark matter halo while simplifying the analysis. Our findings indicate that baryons have a greater impact on the thermal structure of the central region of the halo compared to SIDM scatterings. Furthermore, the new thermal structure caused by baryon contraction leads to cuspier central densities in the Milky Way-like halo due to the removal of thermal support by SIDM scatterings.