Non-parametric Morphologies of Galaxies in the EAGLE Simulation

TL;DR

This study compares the optical morphologies of galaxies in the EAGLE simulation with observations, finding good agreement overall but noting differences in asymmetry and resolution effects, and exploring correlations with kinematic properties.

Contribution

It provides a detailed comparison of non-parametric galaxy morphologies in EAGLE with observational data and other simulations, highlighting strengths and limitations of the simulation.

Findings

EAGLE galaxies' morphologies largely match observations.

Asymmetry values are higher in simulated galaxies.

Gini and Asymmetry are affected by spatial resolution.

Abstract

We study the optical morphology of galaxies in a large-scale hydrodynamic cosmological simulation, the EAGLE simulation. Galaxy morphologies were characterized using non-parametric statistics (Gini, $M_{20}$, Concentration and Asymmetry) derived from mock images computed using a 3D radiative transfer technique and post-processed to approximate observational surveys. The resulting morphologies were contrasted to observational results from a sample of $\log_{10}(M_{*}/M_\odot) > 10$ galaxies at $z \sim 0.05$ in the GAMA survey. We find that the morphologies of EAGLE galaxies reproduce observations, except for asymmetry values which are larger in the simulated galaxies. Additionally, we study the effect of spatial resolution in the computation of non-parametric morphologies, finding that Gini and Asymmetry values are systematically reduced with decreasing spatial resolution. Gini values for lower mass galaxies are especially affected. Comparing against other large scale simulations, the non-parametric statistics of EAGLE galaxies largely agree with those found in IllustrisTNG. Additionally, EAGLE galaxies mostly reproduce observed trends between morphology and star formation rate and galaxy size. Finally, We also find a significant correlation between optical and kinematic estimators of morphologies, although galaxy classification based on an optical or a kinematic criteria results in different galaxy subsets. The correlation between optical and kinematic morphologies is stronger in central galaxies than in satellites, indicating differences in morphological evolution.