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

S. Ramírez Alegría (1,2), A. Marín-Franch (3), & A. Herrero (4,5)

(1) The Millennium Institute of Astrophysics (MAS), Santiago, Chile; (2) Instituto de Astrofísica, Universidad de Valparaíso, Valparaíso, Chile; (3) Centro de Estudios de Física del Cosmos de Aragón (CEFCA), Teruel, Spain; (4) Instituto de Astrofísica de Canarias, Tenerife, Spain; (5) Departamento de Astrofísica, Universidad de La Laguna, Tenerife, Spain.

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 Ks) 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 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.

Reference: A&A, accepted (05/09/14 )
Status: Manuscript has been accepted