Local Star Formation Density Weakly Predicts Young Star Cluster Radii Across Four Galaxies
What Was Observed (Empirical Data)
Researchers cross-matched 325 young star clusters (<10 Myr) from the LEGUS catalog with H-alpha aperture photometry from PHANGS-MUSE across four shared galaxies to measure local star formation rate surface density (Sigma_SFR). Controlling for cluster mass and age, local Sigma_SFR shows a statistically significant correlation with effective cluster radius (beta = 0.079, p = 2 x 10^-4), whereas galaxy-wide specific star formation rate shows no predictive power (p = 0.40). This local environmental effect persists even when accounting for galaxy fixed effects (beta = 0.068, p = 0.001).
The Reality Check (Anti-Hype Analysis)
While statistically significant, the full model including local star formation density, mass, and age explains only 6.1% of the variance in cluster radii under cross-validation (CV R^2 = 0.061), leaving the vast majority of scatter in the mass-radius relation unexplained. Furthermore, the analysis is constrained to a sample of just 325 clusters across four galaxies, meaning local H-alpha surface density is only a minor contributor to cluster structural scatter rather than a definitive predictor.
PRIMARY SOURCE:
arXiv Astrophysics (astro-ph)