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