PHANGS: Constraining Star Formation Timescales Using the Spatial Correlations of Star Clusters and Giant Molecular Clouds

TL;DR

This study investigates the spatial relationship between young star clusters and giant molecular clouds across various galaxy environments, revealing how star formation structures evolve and dissolve within 4-10 million years.

Contribution

It combines high-resolution data from PHANGS-ALMA and PHANGS-HST to analyze the spatial correlations of star clusters and GMCs across multiple galaxies, providing new insights into star formation timescales.

Findings

Star clusters lose association with gas clouds after 4-6 Myr.

Young star clusters show stronger spatial autocorrelation than older populations.

Hierarchical star formation structures dissolve over 10 Myr.

Abstract

In the hierarchical view of star formation, giant molecular gas clouds (GMCs) undergo fragmentation to form small-scale structures made up of stars and star clusters. Here we study the connection between young star clusters and cold gas across a range of extragalactic environments by combining the high resolution (1") PHANGS-ALMA catalogue of GMCs with the star cluster catalogues from PHANGS-HST. The star clusters are spatially matched with the GMCs across a sample of 11 nearby star-forming galaxies with a range of galactic environments (centres, bars, spiral arms, etc.). We find that after 4-6 Myr the star clusters are no longer associated with any gas clouds. Additionally, we measure the autocorrelation of the star clusters and GMCs as well as their cross-correlation to quantify the fractal nature of hierarchical star formation. Young ($\leq$ 10 Myr) star clusters are more strongly autocorrelated on kpc and smaller spatial scales than the >10 Myr stellar populations, indicating that the hierarchical structure dissolves over time.