The Formation and Evolution of Massive Stellar Clusters in IC 4662

TL;DR

This study investigates the formation, properties, and feedback effects of massive stellar clusters in IC 4662 using multiwavelength data, revealing details about their ages, masses, extinction, and dust-gas interactions.

Contribution

It provides a detailed multiwavelength analysis of embedded massive star clusters in IC 4662, highlighting their properties and challenging the view of them as single super star clusters.

Findings

Clusters are ~4 million years old with masses around 3 x 10^5 solar masses.

Clusters exhibit high extinction with A_V ~ 20-25 mag.

Dust is well-mixed with gas, not in a foreground screen.

Abstract

We present a multiwavelength study of the formation of massive stellar clusters, their emergence from cocoons of gas and dust, and their feedback on surrounding matter. Using data that span from radio to optical wavelengths, including Spitzer and Hubble ACS observations, we examine the population of young star clusters in the central starburst region of the irregular Wolf-Rayet galaxy IC 4662. We model the radio-to-IR spectral energy distributions of embedded clusters to determine the properties of their HII regions and dust cocoons (sizes, masses, densities, temperatures), and use near-IR and optical data with mid-IR spectroscopy to constrain the properties of the embedded clusters themselves (mass, age, extinction, excitation, abundance). The two massive star-formation regions in IC 4662 are excited by stellar populations with ages of ~ 4 million years and masses of ~ 3 x 10^5 M_sun (assuming a Kroupa IMF). They have high excitation and sub-solar abundances, and they may actually be comprised of several massive clusters rather than the single monolithic massive compact objects known as Super Star Clusters (SSCs). Mid-IR spectra reveal that these clusters have very high extinctions, A_V ~ 20-25 mag, and that the dust in IC 4662 is well-mixed with the emitting gas, not in a foreground screen.