ARCHITECTS I: Impact of subgrid physics on the simulated properties of the circumgalactic medium

TL;DR

This study compares three different subgrid feedback models in galaxy simulations, revealing that despite similar stellar masses, they produce significantly different circumgalactic medium properties, highlighting the importance of model choice.

Contribution

It systematically analyzes how different subgrid physics models affect the CGM in galaxy simulations, emphasizing the need for careful model selection.

Findings

Delayed cooling leads to ejective feedback and high burstiness.

Mechanical feedback retains most baryons and produces different metal distributions.

Hybrid feedback results in intermediate baryon retention and metal distribution.

Abstract

Galaxy evolution is shaped by star formation and stellar feedback at scales unresolved by current high-resolution cosmological simulations. Precise subgrid models are thus necessary, and different approaches have been developed. However, they are degenerate and often primarily calibrated to reproduce stellar masses from observations. To explore these degeneracies, we perform three cosmological zoom-in radiation-hydrodynamics simulations of the same galaxy within a $5\times10^{11}\rm\ M_\odot$ dark matter halo at $z\sim1$, each with a different subgrid model: mechanical feedback, a combination of mechanical feedback and thermal feedback, and delayed cooling. We calibrate the simulations to match in stellar mass, isolating the effect of the models on the circumgalactic medium (CGM). Our findings demonstrate that despite producing galaxies with comparable stellar masses, the three models lead to distinct feedback modes, resulting in notable variations in the CGM properties. The delayed cooling run is dominated by ejective feedback and exhibits high burstiness, whereas mechanical and the hybrid models primarily feature preventive feedback, respectively acting at the galaxy and halo scales. Delayed cooling reduces the baryon mass to half the universal baryon fraction while mechanical feedback retains most baryons, with the hybrid model standing in between. Delayed cooling also ejects significantly more metals into the CGM than both other models. While for delayed cooling and mechanical feedback metals are almost evenly distributed in the CGM, they are concentrated around satellites in the hybrid model. These discrepancies emphasize the need to design an appropriate subgrid model to understand how stellar feedback regulates galaxy growth.