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The effect of photoionisation feedback on star formation in giant molecular clouds
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| Title: | The effect of photoionisation feedback on star formation in giant molecular clouds |
| Other Titles: | 分子雲における輻射が星形成に与える影響 |
| Authors: | 島, 和宏1 Browse this author |
| Authors(alt): | Shima, Kazuhiro1 |
| Issue Date: | 22-Mar-2018 |
| Publisher: | Hokkaido University |
| Abstract: | Stars form from collapsing cold molecular clouds (GMCs) and can change the physical state of the parent cloud by emitting energy into its surrounding environment. The energy will stop or improve the future star formation by destroying the cloud or triggering stars. Understanding the processes of star formation and the interplay with the parent cloud is therefore very important in astrophysics. The star formation and the effect of feedback should depend on the cloud internal properties. Clouds are turbulent and not uniform gas distributions which leads to multiple star formation sites. The local conditions of the gas around the star formation site can play a key role in determining the star formation. High-density regions that could not be dispersed are then heated by feedback to increase the Jeans mass and lead to more massive star formation. Alternatively, lower density regions could be blown out by feedback, ending the star formation. I focused on how the feedback effect depends on the initial cloud structures. I considered idealised and non-idealised sets of initial conditions and investigated the total effect of feedback on the star formation history. [1] Does feedback help or hinder star formation? The effect of photoionization on star formation in giant molecular clouds (Shima et al. 2017a) I investigated the effect of photoionising feedback both inside idealised and inside more realistic cloud structures extracted from a global galaxy simulation. I showed that feedback can both promote and suppress star formation in the idealised case. On the other hands, star formation is suppressed by feedback in the extracted case because the gas has fragmented into small dense cores by global galaxy tidal interactions and the structures are unaffected by the injection of radiation energy. Instead, the collapse was slowed to reduce the star formation efficiency. [2] The effect of photoionizing feedback on star formation in isolated and colliding clouds (Shima et al. 2017b) I perfomed hydrodynamical simulations of self-gravitating turbulent gas including photoionising feedback and investigate star formation occurring in giant molecular clouds, comparing structures that evolve in isolation versus those produced during a cloud collision. Observational evidence strongly suggests that colliding objects promote the production of massive stars in a short timescale by compressing gas at the interface of the two colliding clouds. Two different collision speeds are investigated and the impact of photoionising radiation from the stars is determined. I find that a colliding system leads to more massive star formation both with and without the addition of feedback, raising overall star formation efficiencies (SFE) by a factor of 10 and steepening the high-mass end of the stellar mass function. This rise in SFE is due to increased turbulent compression during the cloud collision. While feedback can both promote and hinder star formation in the isolated system, it increases the SFE by approximately 1.5 times in the colliding case when the thermal speed of the resulting H II regions matches the shock propagation speed in the collision. |
| Conffering University: | 北海道大学 |
| Degree Report Number: | 甲第13130号 |
| Degree Level: | 博士 |
| Degree Discipline: | 理学 |
| Examination Committee Members: | (主査) 客員准教授 エリザベス・タスカー, 特任教授 羽部 朝男, 特任教授 小笹 隆司, 教授 小林 達夫, 講師 岡本 崇 |
| Degree Affiliation: | 理学院（宇宙理学専攻） |
| Type: | theses (doctoral) |
| URI: | http://hdl.handle.net/2115/73153 |
| Appears in Collections: | 課程博士 (Doctorate by way of Advanced Course) > 理学院(Graduate School of Science)
学位論文 (Theses) > 博士 （理学）
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