Cosmological baryon transfer in the SIMBA simulations

Understand

We present a framework for characterizing the large scale movement of baryons relative to dark matter in cosmological simulations, requiring only the initial conditions and final state of the simulation.

• This is performed using the spread metric which quantifies the distance in the final conditions between initially neighbouring particles, and by analysing the baryonic content of final haloes relative to that of the initial Lagrangian regions defined by their dark matter component.
• Applying this framework to the SIMBA cosmological simulations, we show that 40% (10%) of cosmological baryons have moved $> 1h^{-1}~ {\rm Mpc}^{-1}$ ($3h^{-1}~ {\rm Mpc}^{-1}$) by $z=0$, due primarily to entrainment of gas by jets powered by AGN, with baryons moving up to $12h^{-1}~ {\rm Mpc}^{-1}$ away in extreme cases.
• Baryons decouple from the dynamics of the dark matter component due to hydrodynamic forces, radiative cooling, and feedback processes.