Structural analysis of disk super star clusters of M82: size and profile shape at intermediate ages

TL;DR

This study analyzes the structural parameters of 99 super star clusters in M82, revealing their size and profile shape distributions, and compares these with clusters in other galaxies to understand their evolution.

Contribution

It provides the first detailed characterization of SSC profiles in M82 using HST data and compares these with clusters in LMC and M83 to explore environmental effects.

Findings

Most SSC profiles are best fitted by the Moffat-EFF model.

Core radii follow a log-normal distribution centered at 1.73 pc.

Gamma distribution is also log-normal with a center at 2.88.

Abstract

We present the structural parameters of 99 Super Star Clusters (SSCs) in the Disk of M82. Moffat-EFF, King and Wilson models were fitted using a chi^2 minimisation method to background-subtracted Surface Brightness Profiles (SBPs) in F435W (B), F555W (V), and F814W (I) bands of the Advanced Camera for Surveys (ACS) of the Hubble Space Telescope (HST). The majority of the SSC profiles is best-fitted by the Moffat-EFF profile. The scale parameter rd and the shape parameter gamma in the three filters are identical within the measurement errors. The analysed sample is big enough to allow characterisation of the distributions of core radii Rc and gamma. The obtained distribution of Rc follows a log-normal form, with center and sigma(log(Rc/pc)) being 1.73 pc and 0.25, respectively. The gamma distribution is also log-normal with center and sigma(log(gamma)) being 2.88 and 0.08, respectively. M82 is well-known for the absence of current star formation in its disk, with all disk SSCs older than 50 Myr and hardly any cluster older than ~300 Myr. The derived distributions compare very well with the distributions for intermediate-age clusters in the Large Magellanic Cloud (LMC), which is also a low-mass late-type galaxy similar to M82. On the other hand, the distributions of Rc in both these galaxies are shifted towards larger values as compared to SSCs of similar age in the giant spiral galaxy M83. M82 and LMC also span a narrower range of gamma values as compared to that in M83.