Formation of stellar clusters

TL;DR

This paper explores how star formation is triggered in molecular clouds passing through spiral shocks, leading to the formation and evolution of stellar clusters with detailed properties and growth mechanisms.

Contribution

It introduces a gravitational potential based cluster finding algorithm and provides new insights into cluster formation, mass distribution, and hierarchical merging processes.

Findings

Clusters form along spiral shock ridges every 5-10 pc.

Final cluster masses range from 1,000 to 30,000 solar masses.

More massive clusters grow via hierarchical merging and gas accretion.

Abstract

We investigate the triggering of star formation and the formation of stellar clusters in molecular clouds that form as the ISM passes through spiral shocks. The spiral shock compresses gas into $\sim$100 pc long main star formation ridge, where clusters forming every 5-10 pc along the merger ridge. We use a gravitational potential based cluster finding algorithm, which extracts individual clusters, calculates their physical properties and traces cluster evolution over multiple time steps. Final cluster masses at the end of simulation range between 1000 and 30000 M$_{\odot}$ with their characteristic half-mass radii between 0.1 pc and 2 pc. These clusters form by gathering material from 10-20 pc size scales. Clusters also show a mass - specific angular momentum relation, where more massive clusters have larger specific angular momentum due to the larger size scales, and hence angular momentum from which they gather their mass. The evolution shows that more massive clusters experiences hierarchical merging process, which increases stellar age spreads up to 2-3 Myr. Less massive clusters appear to grow by gathering nearby recently formed sinks, while more massive clusters with their large global gravitational potentials are increasing their mass growth from gas accretion.