摘要
We investigate 25 H II regions that show bubble morphology in 13CO（1-0） and infrared data, to search for quantitative evidence of triggered star formation by processes described by the collect and collapse （CC） and radiatively driven implosion （RDI） models. These H II regions display the morphology of a complete or partial bubble at 8 μm, and are all associated with the molecular clouds that surround them. We found that the electron temperature ranges from 5627 K to 6839 K in these H II regions, and the average electron temperature is 6083 K. The age of these H II regions is from 3.0× 10^5 yr to 1.7 × 10^6 yr, and the mean age is 7.7 × 10^5 yr. Based on the mor- phology of the associated molecular clouds, we divide these H II regions into three groups, which may support CC and RDI models. We select 23 young IRAS sources which have an infrared luminosity of 〉 10^3 Lo in 19 H II regions. In addition, we iden- tify some young stellar objects （including Class I sources）, which are only concen- trated in H II regions G29.007＋0.076, G44.339-0.827 and G47.028＋0.232. The poly- cyclic aromatic hydrocarbon emissions of the three H II regions all show a 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 clustered star forma- tion by an RDI process. In addition, we detect seven molecular outflows in the five H II regions for the first time. These outflow sources may be triggered by the corresponding H II regions.
We investigate 25 H II regions that show bubble morphology in 13CO（1-0） and infrared data, to search for quantitative evidence of triggered star formation by processes described by the collect and collapse （CC） and radiatively driven implosion （RDI） models. These H II regions display the morphology of a complete or partial bubble at 8 μm, and are all associated with the molecular clouds that surround them. We found that the electron temperature ranges from 5627 K to 6839 K in these H II regions, and the average electron temperature is 6083 K. The age of these H II regions is from 3.0× 10^5 yr to 1.7 × 10^6 yr, and the mean age is 7.7 × 10^5 yr. Based on the mor- phology of the associated molecular clouds, we divide these H II regions into three groups, which may support CC and RDI models. We select 23 young IRAS sources which have an infrared luminosity of 〉 10^3 Lo in 19 H II regions. In addition, we iden- tify some young stellar objects （including Class I sources）, which are only concen- trated in H II regions G29.007＋0.076, G44.339-0.827 and G47.028＋0.232. The poly- cyclic aromatic hydrocarbon emissions of the three H II regions all show a 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 clustered star forma- tion by an RDI process. In addition, we detect seven molecular outflows in the five H II regions for the first time. These outflow sources may be triggered by the corresponding H II regions.
基金
Supported by the National Natural Science Foundation of China
