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| Paper: |
Kinematic Perspective on the Formation Process of OB Associations |
| Volume: |
536, The Twelfth Pacific Rim Conference on Stellar Astrophysics |
| Page: |
3 |
| Authors: |
Lim, B. |
| Abstract: |
OB associations are the prime sites of star formation in galaxies, providing clues to the star formation process. We perform a survey of Galactic OB associations to unveil the star formation process taking place on several hundreds of parsec scales in the context of three theoretical models, e.g., the expansion of stellar clusters after rapid gas expulsion, structure formation in turbulent molecular clouds, and feedback- driven star formation. In this survey, the internal structure and stellar kinematics of six OB associations are investigated using Gaia data and high-resolution spectroscopy. These associations have different levels of substructures. Most of the stellar clusters found in such associations show a pattern of expansion, which is related to the origin of low-density stellar haloes around them. On the other hand, several stellar groups are found at the border of H II bubbles. Some of them show receding motions away from ionizing sources. Also, they appear to be younger than stellar clusters hosting the ionizing sources. These observational findings suggest the signature of feedback-driven star formation. The other groups do not show such systematic motions from ionizing sources. It implies that these groups might have spontaneously formed in their current location. In conclusion, our comprehensive results suggest that OB associations may form through two or all of the three processes proposed by the theoretical models, with different contributions. |
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