Evidence for Environmentally Dependent Cluster Disruption in M83

TL;DR

This study uses Hubble Space Telescope imaging to analyze stellar cluster populations in M83, revealing that environmental conditions significantly influence cluster disruption and age distributions, challenging the idea of universal cluster properties.

Contribution

It provides empirical evidence that cluster disruption and age distributions depend on local galactic environment, contrasting with previous assumptions of universality.

Findings

Outer clusters are generally older by tens of Myr than inner clusters.

Many automated detections are associations, not true clusters, dispersing within tens of Myr.

Environmental factors significantly affect cluster age and mass distributions.

Abstract

Using multi-wavelength imaging from the Wide Field Camera 3 on the Hubble Space Telescope we study the stellar cluster populations of two adjacent fields in the nearby face-on spiral galaxy, M83. The observations cover the galactic centre and reach out to ~6 kpc, thereby spanning a large range of environmental conditions, ideal for testing empirical laws of cluster disruption. The clusters are selected by visual inspection to be centrally concentrated, symmetric, and resolved on the images. We find that a large fraction of objects detected by automated algorithms (e.g. SExtractor or Daofind) are not clusters, but rather are associations. These are likely to disperse into the field on timescales of tens of Myr due to their lower stellar densities and not due to gas expulsion (i.e. they were never gravitationally bound). We split the sample into two discrete fields (inner and outer regions of the galaxy) and search for evidence of environmentally dependent cluster disruption. Colour-colour diagrams of the clusters, when compared to simple stellar population models, already indicate that a much larger fraction of the clusters in the outer field are older by tens of Myr than in the inner field. This impression is quantified by estimating each cluster's properties (age, mass, and extinction) and comparing the age/mass distributions between the two fields. Our results are inconsistent with "universal" age and mass distributions of clusters, and instead show that the ambient environment strongly affects the observed populations.