Multiwavelength Observations of Massive Stellar Cluster Candidates in the Galaxy

TL;DR

This study uses multiwavelength observations, including radio and infrared data, to characterize six candidate massive stellar clusters in the Galaxy, revealing they are likely intermediate-mass clusters rather than the most massive ones.

Contribution

It provides detailed physical characterization of six cluster candidates using combined radio and infrared observations, enhancing understanding of their nature and mass.

Findings

Candidates have less powerful Lyman ionizing fluxes.

They ionize less H II mass than known massive clusters.

Candidates are consistent with intermediate-mass clusters.

Abstract

The Galaxy appears to be richer in young, massive stellar clusters than previously known, due to advances in infrared surveys which have uncovered deeply embedded regions of star formation. Young, massive clusters can significantly impact the surrounding interstellar medium (ISM) and hence radio observations can also be an important tracer of their activity. Several hundred cluster candidates are now known by examining survey data. Here we report on multiwavelength observations of six of these candidates in the Galaxy. We carried out 4.9 and 8.5 GHz VLA observations of the radio emission associated with these clusters to obtain the physical characteristics of the surrounding gas, including the Lyman continuum photon flux and ionized gas mass. Spitzer Infrared Array Camera observations were also made of these regions, and provide details on the stellar population as well as the dust continuum and polycyclic aromatic hydrocarbon emission. When compared to the known young, massive clusters in the Galaxy, the six cluster candidates have less powerful Lyman ionizing fluxes and ionize less of the H II mass in the surrounding ISM. Therefore, these cluster candidates appear to be more consistent with intermediate-mass clusters (10^3-10^4 Msun).