Triggered massive star formation associated with the bubble HII region
  Sh2-39 (N5)
  Aiming at studying the physical properties of Galactic IR bubbles and to
explore their impact in triggering massive star formation, we perform a
multiwavelength analysis of the bubble HII region Sh2-39 (N5) and its environs.
To analyze the molecular gas we use CO(3-2) and HCO+(4-3) line data obtained
with the ASTE telescope. To study the physical characteristics of the dust, we
make use of archival data from ATLASGAL, Herschel, and MSX, while the ionized
gas was studied making use of NVSS data. We use public IR point source catalogs
to search for candidate YSOs in the region. To investigate the stellar cluster
[BDS2003]6 we use IR spectroscopic data obtained with the ARCoIRIS
spectrograph, and new available IR Ks band observations from VVVX survey. The
new ASTE observations allowed the molecular gas component in the velocity range
from 30 km/s to 46 km/s, associated with Sh2-39, to be studied in detail. We
have identified four molecular clumps, that were likely formed by the expansion
of the ionization front, and determined some of their physical and dynamical
properties. Clumps having HCO+ and 870 micron counterparts show evidence of
gravitational collapse. We identified several candidate YSOs across the
molecular component. Their spatial distribution, as well as the fragmentation
time derived for the collected layers of the molecular gas, suggest that
massive star formation might have been triggered by the expansion of the nebula
via the collect and collapse mechanism. The spectroscopical distance obtained
for the stellar cluster [BDS2003]6, placed over one of the collapsing clumps,
reveals that this cluster is physically associated with the neabula and gives
more support to the triggered massive star formation scenario. A radio
continuum data analysis indicates that the nebula is older and expands at lower
velocity than typical Galactic IR bubbles.
