Mass Functions of Giant Molecular Clouds and Young Star Clusters in Six Nearby Galaxies
Angus Mok, Rupali Chandar, S. Michael Fall
Abstract
Abstract We compare the mass functions of young star clusters (ages ≤ 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, , 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 ( ). 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 relatively small range of indices β PL = −2.3 ± 0.3 for our GMC sample and β PL = −2.0 ± 0.3 for the cluster sample. This result, that , is consistent with theoretical predictions for cluster formation and suggests that the star formation efficiency is largely independent of mass in the GMCs.