The properties, origin and evolution of stellar clusters in galaxy simulations and observations

TL;DR

This study compares the properties and evolution of stellar clusters in galaxy simulations with observations, revealing insights into cluster formation, dispersal, and the influence of galactic environment, with some limitations in modeling realism.

Contribution

It introduces a novel approach to model clusters with multiple particles in galaxy simulations and compares their properties with observational data.

Findings

Older stars and clusters are more associated with spiral structures in simulations.

Simulated cluster evolution closely follows their natal gas clouds.

Most clusters disperse quickly, aligning with observational evidence.

Abstract

We investigate the properties and evolution of star particles in two simulations of isolated spiral galaxies, and two galaxies from cosmological simulations. Unlike previous numerical work, where typically each star particle represents one `cluster', for the isolated galaxies we are able to model features we term `clusters' with groups of particles. We compute the spatial distribution of stars with different ages, and cluster mass distributions, comparing our findings with observations including the recent LEGUS survey. We find that spiral structure tends to be present in older (100s Myrs) stars and clusters in the simulations compared to the observations. This likely reflects differences in the numbers of stars or clusters, the strength of spiral arms, and whether the clusters are allowed to evolve. Where we model clusters with multiple particles, we are able to study their evolution. The evolution of simulated clusters tends to follow that of their natal gas clouds. Massive, dense, long-lived clouds host massive clusters, whilst short-lived clouds host smaller clusters which readily disperse. Most clusters appear to disperse fairly quickly, in basic agreement with observational findings. We note that embedded clusters may be less inclined to disperse in simulations in a galactic environment with continuous accretion of gas onto the clouds than isolated clouds and correspondingly, massive young clusters which are no longer associated with gas tend not to occur in the simulations. Caveats of our models include that the cluster densities are lower than realistic clusters, and the simplistic implementation of stellar feedback.