TRIGGERED STAR FORMATION AROUND MID-INFRARED BUBBLES IN THE G8.14+0.23 H ii REGION

Mid-infrared 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 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 timescale 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 cannot 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 M☉) 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.