Extremely rapid star cluster disruption in high-shear circumnuclear starburst rings: the unusual case of NGC 7742

TL;DR

This study reveals that the high-shear environment in NGC 7742's starburst ring causes rapid disruption of young star clusters, leading to a lognormal mass distribution similar to old globular clusters, contrary to typical power-law distributions.

Contribution

It demonstrates that extreme environmental conditions can accelerate star cluster disruption, resulting in a lognormal mass function at very young ages, a novel finding in star cluster evolution.

Findings

Star cluster mass functions are lognormal at all ages, including <15 Myr.

High-shear conditions may significantly speed up cluster disruption.

Disruption may be driven by high density and shear from counterrotating gas disk.

Abstract

All known mass distributions of recently formed star cluster populations resemble a "universal" power-law function. Here we assess the impact of the extremely disruptive environment in NGC 7742's circumnuclear starburst ring on the early evolution of the galaxy's high-mass (~10^5-10^7 Msun) star cluster population. Surprisingly, and contrary to expectations, at all ages -- including the youngest, <15 Myr -- the cluster mass functions are robustly and verifiably represented by lognormal distributions that resemble those commonly found only for old, evolved globular cluster systems in the local Universe. This suggests that the high-shear conditions in the NGC 7742 starburst ring may significantly speed up dynamical star cluster destruction. This enhanced mass-dependent disruption rate at very young ages might be caused by a combination of the starburst ring's high density and the shear caused by the counterrotating gas disk in the galaxy's inner region.