Exploring the Angular Momentum -- Atomic Gas Content Connection with EAGLE and IllustrisTNG

TL;DR

This study uses EAGLE and IllustrisTNG simulations to explore the relationship between angular momentum, baryonic mass, and atomic gas fraction in galaxies, finding strong agreement between simulations and observations at higher gas fractions.

Contribution

It demonstrates the consistency of EAGLE and TNG simulations with observational data and highlights potential deviations at low gas fractions, suggesting complex galaxy evolution processes.

Findings

Simulations agree well with observations for gas fractions > 0.01.

Discrepancies exist between models and observations at low gas fractions.

A possible disconnect between angular momentum and gas content in gas-poor galaxies.

Abstract

We use the EAGLE (Evolution and Assembly of GaLaxies and their Environments) and IllustrisTNG (The Next Generation) cosmological simulations to investigate the properties of the baryonic specific angular momentum (j), baryonic mass (M) and atomic gas fraction ($f_{\rm{atm}}$) plane for nearby galaxies. We find EAGLE and TNG to be in excellent agreement with each other. These simulations are also consistent with the results obtained with xGASS (eXtended GALEX Arecibo SDSS Survey) for gas fractions greater than 0.01. This implies that the disagreements previously identified between xGASS and predictions from simple analytical disc stability arguments also holds true for EAGLE and TNG. For lower gas fraction (the regime currently unconstrained by observations), both simulations deviate from the plane but still maintain good agreement with each other. Despite the challenges posed by resolution limits at low gas fractions, our findings suggest a potential disconnect between angular momentum and gas fraction in the gas-poor regime, implying that not all gas-poor galaxies have low specific angular momentum.