Rhea-RT: Dynamical impact of Central Molecular Zone conditions on ISM properties and stellar feedback coupling

TL;DR

This study uses radiation MHD simulations to explore how the unique conditions of the Central Molecular Zone affect star formation, feedback, and molecular cloud evolution, revealing the importance of orbital dynamics and shear.

Contribution

It provides the first detailed simulation-based analysis of the impact of CMZ conditions on ISM properties and stellar feedback coupling in a Milky Way-like galaxy.

Findings

Star formation regulation differs due to short orbital times and shear in the CMZ.

Stellar feedback acts as a turbulence background rather than disrupting molecular clouds.

Young stellar associations are quickly sheared apart, affecting feedback processes.

Abstract

The Central Molecular Zone (CMZ) is an extreme star formation environment, characterized by higher density, higher turbulence, stronger orbital shear, and stronger magnetic field strength than the Solar neighborhood. Whether classical theories of star formation hold within this extreme environment is still debated. In order to assess the impact of these different conditions on the interstellar medium (ISM) and on star formation, we present radiation MHD arepo simulations of a Milky Way-type galaxy. We set up a high-resolution ($M_{\rm cell}=20$ M$_\odot$) region in a ring around the Solar radius, as well as in the barred region of the Galaxy to have a coherent comparison between the CMZ and the Solar neighborhood. Although the high densities and strong levels of turbulence influence star formation and feedback, we find that a key difference in the regulation of star formation between the two environments comes from the short orbital times and the strong shear present in the CMZ. In particular, we highlight the role of the quick dynamical decoupling of stars and gas that leads to periodic re-embedding events in the early lifetimes of radiating O stars. Young stellar associations get efficiently sheared apart such that the ISM is deprived of the compounding effect of radiation and supernovae in disrupting molecular clouds. This changes dramatically the evolution of giant molecular clouds and how feedback can regulate star formation in the CMZ. Stellar feedback is no longer directly coupled to the molecular cloud from which they formed and no strong and disruptive superbubbles can develop. Instead, the feedback rather acts as a background source of turbulence.