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The effect of radiation pressure from massive stars and black holes in the dusty interstellar medium
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| Title: | The effect of radiation pressure from massive stars and black holes in the dusty interstellar medium |
| Other Titles: | ダスト存在下での大質量星やブラックホールからの輻射圧の影響 |
| Authors: | 一色, 翔平 Browse this author |
| Issue Date: | 25-Mar-2020 |
| Publisher: | Hokkaido University |
| Abstract: | Dust is one of the important elements in astrophysics. Radiation pressure on dust grains affects the gas dynamics in star formation and black hole growth. We develop the numerical radiation hydrodynamic code to reveal the effect of radiation pressure from massive stars and black holes in the dusty interstellar medium. The results are as follows:
[1] Radiation feedback in dusty clouds (Ishiki & Okamoto 2017)
We have investigated the impact of photoionization and radiation pressure on a dusty star-forming cloud using one-dimensional radiation hydrodynamic simulations, which include absorption and re-emission of photons by dust. We find that, in a cloud of mass 105 M⊙ and radius 17 pc, the effect of radiation pressure is negligible when star formation efficiency is 2 %. The importance of radiation pressure increases with increasing star formation efficiency or an increasing dust-to-gas mass ratio. The net effect of radiation feedback, however, becomes smaller with the increasing dust-to-gas mass ratio, since the absorption of ultra-violet photons by dust grains suppresses photoionization and hence photoheating.
[2] The effect of radiation pressure on spatial distribution of dust inside HII regions (Ishiki et al. 2018)
We investigate the impact of radiation pressure on spatial dust distribution inside Hii regions using one-dimensional radiation hydrodynamic simulations, which include absorption and re-emission of photons by dust. In order to investigate grain size effects as well, we introduce two additional fluid components describing large and small dust grains in the simulations. Relative velocity between dust and gas strongly depends on the drag force. We include collisional drag force and coulomb drag force. We fjnd that, in a compact Hii region, a dust cavity region is formed by radiation pressure. Resulting dust cavity sizes (～ 0.2 pc) agree with observational estimates reasonably well. In addition, in a cloud of mass 105 M⊙, we find that the radiation pressure changes the grain size distribution inside Hii regions. Since large (0.1 ㎛ ) dust grains are accelerated more efficiently than small (0.01 ㎛) grains, the large to small grain mass ratio becomes smaller by an order of magnitude compared with the initial one.
[3] Growth of massive black holes in dusty clouds: impacts of relative velocity between dust and gas
We investigate the impacts of the relative motions between dust and gas on the accretion rate onto Intermediate Mass Black Holes (IMBHs) by using one-dimensional radiation hydrodynamic simulations. To investigate the effect of grain size on the gas accretion, we introduce two additional fluid components to gas, which describe large (0.1 ㎛) and small (0.01 ㎛) dust grains in the simulations. We find that the accretion rate is reduced due to the radiation force compared with dust free case. We also find that the dust-to-gas mass ratio significantly changes within Hii regions because of the relative motions of dust and gas. The decoupling of dust from gas alleviates the suppression of black hole growth compared with the complete coupling case. This effect may allow moderate growth of black holes even in dusty clouds. In addition, relative motion between dust and gas affects the spectral energy distribution (SED) owing to dust re-emission at wavelength
λ～10 ㎛. |
| Conffering University: | 北海道大学 |
| Degree Report Number: | 甲第13907号 |
| Degree Level: | 博士 |
| Degree Discipline: | 理学 |
| Examination Committee Members: | (主査) 准教授 徂徠 和夫, 教授 小林 達夫, 教授 倉本 圭, 講師 岡本 崇 |
| Degree Affiliation: | 理学院（宇宙理学専攻） |
| Type: | theses (doctoral) |
| URI: | http://hdl.handle.net/2115/78439 |
| 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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