The impact of baryonic physics on the abundance, clustering, and concentration of halos

Understand

We examine the impact of baryonic physics on the halo distribution in hydrodynamic simulations (Illustris, IllustrisTNG, and EAGLE), particularly with regards to how it differs from that in dark matter only (DMO) simulations.

• We find that, in general, DMO simulations produce halo mass functions (HMF) that are shifted to higher halo masses than their hydrodynamic counterparts, due to the lack of baryonic physics.
• However, the exact nature of this mass shift is a complex function of mass, halo definition, redshift, and larger-scale environment, and it also depends on the specifics of the baryonic physics implemented in the simulation.
• We present fitting formulae for the corrections one would need to apply to each DMO halo catalogue in order to reproduce the HMF found in its hydrodynamic counterpart.