Validating the CROCODILE model within the AGORA galaxy simulation framework

TL;DR

This paper validates the GADGET4-OSAKA galaxy simulation code within the AGORA framework, demonstrating improvements in modeling stellar feedback and circumgalactic medium, and contributing a new simulation data point for galaxy evolution studies.

Contribution

It provides a systematic comparison and validation of GADGET4-OSAKA against its predecessor, highlighting the importance of specific feedback models and contributing to the AGORA CosmoRun suite.

Findings

Mechanical momentum injection suppresses gas fragmentation and regulates star formation.

Stochastic thermal heating creates a multiphase circumgalactic medium.

The validated simulation matches observed stellar mass growth history.

Abstract

Numerical galaxy formation simulations are sensitive to numerical methods and sub-grid physics models, making code comparison projects essential for quantifying uncertainties. Here, we evaluate GADGET4-OSAKA within the AGORA project framework by conducting a systematic comparison with its predecessor. We perform an isolated disk galaxy and a cosmological zoom-in run of a Milky Way-mass halo, following the multi-step AGORA calibration procedure. By systematically deconstructing the updated stellar feedback model, we demonstrate that mechanical momentum injection is necessary to suppress unphysical gas fragmentation and regulate star formation, yielding agreement with the Kennicutt-Schmidt relation. Meanwhile, stochastic thermal heating is essential for driving a hot, metal-enriched gaseous halo, thereby creating a multiphase circumgalactic medium that is absent in the predecessor code. In the cosmological context, we calibrate the simulation to match the stellar mass growth history targeted by the AGORA collaboration. The validated GADGET4-OSAKA simulation has been contributed to the AGORA CosmoRun suite, providing a new data point for understanding the impact of numerical and physical modeling choices on galaxy evolution.