Cloud angular momentum and effective viscosity in global SPH simulations with feedback

TL;DR

This study uses global SPH simulations of isolated galaxies to analyze how feedback influences molecular cloud formation, evolution, and interactions, revealing feedback's role in turbulence, cloud destruction, and angular momentum distribution.

Contribution

It provides new insights into how feedback affects cloud dynamics, interactions, and the viscous time-scale, challenging previous estimates and highlighting the importance of feedback in galaxy simulations.

Findings

Feedback leads to younger, less massive clouds with more retrograde rotation.

Cloud interactions' effects on angular momentum depend on feedback presence.

Viscous time-scale increases with feedback strength, but remains much shorter than previous estimates.

Abstract

We examine simulations of isolated galaxies to analyse the effects of localised feedback on the formation and evolution of molecular clouds. Feedback contributes to turbulence and the destruction of clouds, leading to a population of clouds that is younger, less massive, and with more retrograde rotation. We investigate the evolution of clouds as they interact with each other and the diffuse ISM, and determine that the role of cloud interactions differs strongly with the presence of feedback: in models without feedback, scattering events dramatically increase the retrograde fraction, but in models with feedback, mergers between clouds may slightly increase the prograde fraction. We also produce an estimate of the viscous time-scale due to cloud-cloud collisions, which increases with increasing strength of feedback (~20 Gyr vs ~10 Gyr), but is still much smaller than previous estimates (~1000 Gyr); although collisions become more frequent with feedback, less energy is lost in each collision than in the models without feedback.