Star Cluster Formation and Destruction in the Merging Galaxy NGC 3256

TL;DR

This study analyzes young star clusters in the merging galaxy NGC 3256, revealing their power-law luminosity and mass functions, rapid disruption rates, and comparing cluster formation efficiency with other galaxies.

Contribution

It provides the first detailed analysis of cluster properties in NGC 3256 and compares cluster formation efficiency metrics across galaxies with varying star formation rates.

Findings

Cluster luminosity and mass functions follow power laws similar to quiescent galaxies.

Approximately 80% of clusters are disrupted each decade in age.

The CMF/SFR statistic aligns with galaxies of lower star formation rates.

Abstract

We use the Advanced Camera for Surveys on the Hubble Space Telescope to study the rich population of young massive star clusters in the main body of NGC 3256, a merging pair of galaxies with a high star formation rate (SFR) and SFR per unit area ($\Sigma_{\rm{SFR}}$). These clusters have luminosity and mass functions that follow power laws, $dN/dL \propto L^{\alpha}$ with $\alpha = -2.23 \pm 0.07$, and $dN/dM \propto M^{\beta}$ with $\beta = -1.86 \pm 0.34$ for $\tau < 10$ Myr clusters, similar to those found in more quiescent galaxies. The age distribution can be described by $dN/d\tau \propto \tau ^ \gamma$, with $\gamma \approx -0.67 \pm 0.08$ for clusters younger than about a few hundred million years, with no obvious dependence on cluster mass. This is consistent with a picture where $\sim 80 \%$ of the clusters are disrupted each decade in time. We investigate the claim that galaxies with high $\Sigma_{\rm{SFR}}$ form clusters more efficiently than quiescent systems by determining the fraction of stars in bound clusters ($\Gamma$) and the CMF/SFR statistic (CMF is the cluster mass function) for NGC 3256 and comparing the results with those for other galaxies. We find that the CMF/SFR statistic for NGC 3256 agrees well with that found for galaxies with $\Sigma_{\rm{SFR}}$ and SFRs that are lower by $1-3$ orders of magnitude, but that estimates for $\Gamma$ are only robust when the same sets of assumptions are applied. Currently, $\Gamma$ values available in the literature have used different sets of assumptions, making it more difficult to compare the results between galaxies.