Simulations of the star-forming molecular gas in an interacting M51-like galaxy

TL;DR

This study uses high-resolution simulations of an M51-like galaxy to explore how galaxy interactions influence molecular cloud formation and star formation, emphasizing the dominant role of feedback in small-scale ISM regulation.

Contribution

It presents the first detailed simulation of GMCs in an interacting galaxy with self-consistent chemistry, star formation, and feedback at sub-parsec resolution.

Findings

Galaxy interaction induces large-scale gas flows and spiral arms.

Gas fractions in ISM phases are mainly unaffected by interactions.

Small-scale GMC behavior is governed by feedback self-regulation.

Abstract

We present here the first of a series of papers aimed at better understanding the evolution and properties of giant molecular clouds (GMCs) in a galactic context. We perform high resolution, three-dimensional {\sc arepo} simulations of an interacting galaxy inspired by the well-observed M51 galaxy. Our fiducial simulations include a non-equilibrium, time-dependent, chemical network that follows the evolution of atomic and molecular hydrogen as well as carbon and oxygen self-consistently. Our calculations also treat gas self-gravity and subsequent star formation (described by sink particles), and coupled supernova feedback. In the densest parts of the simulated interstellar medium (ISM) we reach sub-parsec resolution, granting us the ability to resolve individual GMCs and their formation and destruction self-consistently throughout the galaxy. In this initial work we focus on the general properties of the ISM with a particular focus on the cold star-forming gas. We discuss the role of the interaction with the companion galaxy in generating cold molecular gas and controlling stellar birth. We find that while the interaction drives large-scale gas flows and induces spiral arms in the galaxy, it is of secondary importance in determining gas fractions in the different ISM phases and the overall star-formation rate. The behaviour of the gas on small GMC scales instead is mostly controlled by the self-regulating property of the ISM driven by coupled feedback.