The NGC 7742 star cluster luminosity function: A population analysis revisited

TL;DR

This study revisits the star cluster luminosity function in NGC 7742's starburst ring, confirming a turnover in luminosity distribution especially among the youngest clusters, highlighting unusual population characteristics.

Contribution

It provides a luminosity-based analysis confirming a turnover in the cluster luminosity function, challenging previous mass-based assessments and emphasizing the unique nature of this cluster population.

Findings

Confirmed a turnover in the luminosity function above the completeness limit.

Youngest clusters show the most significant deviation from typical power-law distributions.

Highlights the importance of using luminosities over masses for population analysis.

Abstract

We re-examine the properties of the star cluster population in the circumnuclear starburst ring in the face-on spiral galaxy NGC 7742, whose young cluster mass function has been reported to exhibit significant deviations from the canonical power law. We base our reassessment on the clusters' luminosities (an observational quantity) rather than their masses (a derived quantity), and confirm conclusively that the galaxy's starburst-ring clusters---and particularly the youngest subsample, $\log(t \mbox{ yr}^{-1}) \le 7.2$---show evidence of a turnover in the cluster luminosity function well above the 90\% completeness limit adopted to ensure the reliability of our results. This confirmation emphasises the unique conundrum posed by this unusual cluster population.