Mass Functions of Giant Molecular Clouds and Young Star Clusters in Six Nearby Galaxies

Angus Mok; Rupali Chandar; S. Michael Fall

doi:10.3847/1538-4357/ab7a14

paper

Mass Functions of Giant Molecular Clouds and Young Star Clusters in Six Nearby Galaxies

arXiv:2004.02698 · doi:10.3847/1538-4357/ab7a14

Abstract

We compare the mass functions of young star clusters (ages $\leq 10$ Myr) and giant molecular clouds (GMCs) in six galaxies that cover a large range in mass, metallicity, and star formation rate (LMC, M83, M51, NGC 3627, the Antennae, and NGC 3256). We perform maximum-likelihood fits of the Schechter function, $ψ (M) = d N / d M \propto M^{β} exp (- M / M_{*})$ , to both populations. We find that most of the GMC and cluster mass functions in our sample are consistent with a pure power-law distribution ( $M_{*} \to \infty$ ). M51 is the only galaxy that shows some evidence for an upper cutoff ( $M_{*}$ ) in both populations. Therefore, physical upper mass cutoffs in populations of both GMCs and clusters may be the exception rather than the rule. When we perform power-law fits, we find a range of indices $β_{PL} = - 2.3 \pm 0.3$ for our GMC sample and $β_{PL} = - 2.0 \pm 0.3$ for the cluster sample. This result, that $β_{Clusters} \approx β_{GMC} \approx - 2$ , is consistent with theoretical predictions for cluster formation and suggests that the star-formation efficiency is largely independent of mass in the GMCs.

26 pages, 10 figures; accepted for publication in the Astrophysical Journal

Mass Functions of Giant Molecular Clouds and Young Star Clusters in Six Nearby Galaxies

Abstract

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