Evolution of star clusters with initial bulk rotation via N-body simulations

TL;DR

This study uses N-body simulations to explore how initial bulk rotation influences the early evolution, morphology, and angular momentum transport in star clusters with primordial binaries, providing synthetic observations for future comparison.

Contribution

It is the first detailed simulation-based analysis of how initial bulk rotation affects star cluster evolution, morphology, and angular momentum dynamics with primordial binaries.

Findings

Rapid rotation leads to core collapse and elongated structures.

Angular momentum is transported outward over time.

Bulk rotation effects diminish over two-body relaxation times.

Abstract

Young star clusters can inherit bulk rotation from the molecular clouds from which they have formed. This rotation can affect the long-term evolution of a star cluster and its constituent stellar populations. In this study, we aim to characterize the effects of different degrees of initial rotation on star clusters with primordial binaries. The simulations are performed using NBODY6++GPU. We find that initial rotation strongly affects the early evolution of star clusters. Rapidly rotating clusters show angular momentum transport from the inner parts to the outskirts, resulting in a core collapse. Angular momentum transport is accompanied by a highly elongated bar-like structure morphology. The effects of bulk rotation are reduced on the timescale of two-body relaxation. Rotating and non-rotating clusters experience changes in the direction of angular momentum near the dissolution and early evolution due to the tidal field, respectively. We present synthetic observations of simulated clusters for comparison with future observations in filters of Gaia, CSST, and HST. This work shows the effects of bulk rotation on systems with primordial binaries and could be used for the identification of rotation signatures in observed open clusters.