The EAGLE simulations of galaxy formation: calibration of subgrid physics and model variations

TLDR

The study explores the parameter space of the EAGLE cosmological simulation project by running thirteen simulations. Thirteen periodic‑box simulations were run, with four varying subgrid energetic feedback models calibrated to match the z≈0.1 galaxy stellar mass function, and a reference model injecting more energy into high‑density gas to reduce radiative losses; the remaining nine simulations varied individual parameters of the reference model. The reference model successfully reproduces observed galaxy sizes and scaling relations, whereas three simulations fail to form extended discs due to numerical radiative losses, and varying single parameters demonstrates their impact on galaxy properties.

Abstract

We present results from thirteen cosmological simulations that explore the parameter space of the "Evolution and Assembly of GaLaxies and their Environments" (EAGLE) simulation project. Four of the simulations follow the evolution of a periodic cube L = 50 cMpc on a side, and each employs a different subgrid model of the energetic feedback associated with star formation. The relevant parameters were adjusted so that the simulations each reproduce the observed galaxy stellar mass function at z = 0.1. Three of the simulations fail to form disc galaxies as extended as observed, and we show analytically that this is a consequence of numerical radiative losses that reduce the efficiency of stellar feedback in high-density gas. Such losses are greatly reduced in the fourth simulation - the EAGLE reference model - by injecting more energy in higher density gas. This model produces galaxies with the observed size distribution, and also reproduces many galaxy scaling relations. In the remaining nine simulations, a single parameter or process of the reference model was varied at a time. We find that the properties of galaxies with stellar mass