Masgomas-4: Physical characterization of a double-core obscured cluster with a massive and very young stellar population

TL;DR

This paper characterizes Masgomas-4, a newly discovered double-core obscured star cluster in the Milky Way, revealing its physical parameters, young massive stellar population, and ongoing star formation activity.

Contribution

It provides the first detailed physical characterization of Masgomas-4, including distance, size, mass, age, and stellar content, using near-IR photometry and spectroscopy.

Findings

Cluster distance estimated at ~1.9 kpc

Presence of a very young, massive stellar population

Detection of pre-main-sequence Herbig Ae/Be stars

Abstract

The discovery of new, obscured massive star clusters has changed our understanding of the Milky Way star-forming activity from a passive to a very active star-forming machine. The search for these obscured clusters is strongly supported by the use of all-sky, near-IR surveys. The main goal of the MASGOMAS project is to search for and study unknown, young, and massive star clusters in the Milky Way, using near-IR data. Here we try to determine the main physical parameters (distance, size, total mass, and age) of Masgomas-4, a new double-core obscured cluster. Using near-IR photometry ($J$, $H$, and $K_S$) we selected a total of 21 stars as OB-type star candidates. Multi-object, near-IR follow-up spectroscopy allowed us to carry out the spectral classification of the OB-type candidates. Of the 21 spectroscopically observed stars, ten are classified as OB-type stars, eight as F- to early G-type dwarf stars, and three as late-type giant stars. Spectroscopically estimated distances indicate that the OB-type stars belong to the same cluster, located at a distance of $1.90^{+1.28}_{-0.90}$ kpc. Our spectrophotometric data confirm a very young and massive stellar population, with a clear concentration of pre-main-sequence massive candidates (Herbig Ae/Be) around one of the cluster cores. The presence of a surrounding HII cloud and the Herbig Ae/Be candidates indicate an upper age limit of 5 Myr.