Multi-wavelength study of triggered star formation around 25 H II
  regions
  We have investigated 25 H II regions with bubble morphology in 13CO(1-0) and
infrared data, to search the quantitative evidence for the triggering star
formation by collect and collapse (CC) and radiatively driven implosion (RDI)
models. These H II regions display the morphology of the complete or partial
bubble at 8 um, which all are associated with the surrounding molecular clouds.
We obtained that the electron temperature ranges from 5627 K to 6839 K in these
H II regions, and the averaged electron temperature is 6083 K. The age of these
H II regions is from 3.0\times10^{5} yr to 1.7\times10^{6} yr, and the mean age
is 7.7\times10^{5} yr. Based on the morphology of the associated molecular
clouds, we divided these H II regions into three groups, which may support CC
and RDI models. We selected 23 young IRAS sources with the infrared luminosity
of >10^{3}L_{\odot} in 19 H II regions. In addition, we identified some young
stellar objects (including Class I sources), which are concentrated only in H
II regions G29.007+0.076, G44.339-0.827, and G47.028+0.232. The polycyclic
aromatic hydrocarbons (PAHs) emission of the three H II regions all show the
cometary globule. Comparing the age of each H II region with the characteristic
timescales for star formation, we suggest that the three H II regions can
trigger the clustered star formation by RDI process. In addition, we for the
first time detected seven molecular outflows in the five H II regions. These
outflow sources may be triggered by the corresponding H II regions.
