Massive stars in the Cl 1813-178 Cluster. An episode of massive star formation in the W33 complex

TL;DR

This paper reports the discovery and analysis of a new young massive stellar cluster in the W33 complex, revealing a diverse population of evolved massive stars and providing insights into massive star formation in the Galaxy.

Contribution

First detailed study of the Cl 1813-178 cluster, identifying its stellar content and linking it to the W33 complex, advancing understanding of massive star formation.

Findings

Detected a variety of massive stars including Wolf-Rayet and luminous blue variable.

Estimated the cluster's age at 4-4.5 million years and mass around 10,000 solar masses.

Identified the cluster as the first in the W33 complex, with associated supernova remnants.

Abstract

Young massive (M >10^4 Msun) stellar clusters are a good laboratory to study the evolution of massive stars. Only a dozen of such clusters are known in the Galaxy. Here we report about a new young massive stellar cluster in the Milky Way. Near-infrared medium-resolution spectroscopy with UIST on the UKIRT telescope and NIRSPEC on the Keck telescope, and X-ray observations with the Chandra and XMM satellites, of the Cl 1813-178 cluster confirm a large number of massive stars. We detected 1 red supergiant, 2 Wolf-Rayet stars, 1 candidate luminous blue variable, 2 OIf, and 19 OB stars. Among the latter, twelve are likely supergiants, four giants, and the faintest three dwarf stars. We detected post-main sequence stars with masses between 25 and 100 Msun. A population with age of 4-4.5 Myr and a mass of ~10000 Msun can reproduce such a mixture of massive evolved stars. This massive stellar cluster is the first detection of a cluster in the W33 complex. Six supernova remnants and several other candidate clusters are found in the direction of the same complex.