How to Zoom: Bias, Contamination, and Lagrange Volumes in Multimass Cosmological Simulations

Understand

We perform a suite of multimass cosmological zoom simulations of individual dark matter halos and explore how to best select Lagrangian regions for resimulation without contaminating the halo of interest with low-resolution particles.

• Such contamination can lead to significant errors in the gas distribution of hydrodynamical simulations, as we show.
• For a fixed Lagrange volume, we find that the chance of contamination increases systematically with the level of zoom.
• In order to avoid contamination, the Lagrangian volume selected for resimulation must increase monotonically with the resolution difference between parent box and the zoom region.