Triggered star formation around mid-infrared bubbles in G8.14+0.23 H II
  region
  Mid-infrared (MIR) shells or bubbles around expanding H II regions have
received much attention due to their ability to initiate a new generation of
star formation. We present multi-wavelength observations around two bubbles
associated with a southern massive star-forming (MSF) region G8.14+0.23, to
investigate the triggered star formation signature on the edges of the bubbles
by the expansion of the H II region. We have found observational signatures of
the collected molecular and cold dust material along the bubbles and the
12CO(J=3-2) velocity map reveals that the molecular gas in the bubbles is
physically associated around the G8.14+0.23 region. We have detected 244 young
stellar objects (YSOs) in the region and about 37% of these YSOs occur in
clusters. Interestingly, these YSO clusters are associated with the collected
material on the edges of the bubbles. We have found good agreement between the
dynamical age of the H II region and the kinematical time scale of bubbles
(from the 12CO(J=3-2) line data) with the fragmentation time of the accumulated
molecular materials to explain possible "collect-and-collapse" process around
the G8.14+0.23 region. However, one can not entirely rule out the possibility
of triggered star formation by compression of the pre-existing dense clumps by
the shock wave. We have also found two massive embedded YSOs (about 10 and 22
Msolar) which are associated with the dense fragmented clump at the interface
of the bubbles. We conclude that the expansion of the H II region is also
leading to the formation of these two young massive embedded YSOs in the
G8.14+0.23 region.
