| Project/Area Number |
17540217
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Astronomy
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| Research Institution | Kobe University |
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Principal Investigator |
NAKAGAWA Yoshitsugu Kobe University, Faculty of Science, Professor, 理学部, 教授 (30172282)
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| Co-Investigator(Kenkyū-buntansha) |
MATSUDA Takuya Kobe University, Faculty of Science, Emeritus Professor, 理学部, 名誉教授 (20026206)
AIKAWA Yuri Kobe University, Faculty of Science, Research Associate, 理学部, 助手 (40324909)
野村 英子 神戸大学, 大学院自然科学研究科, COE研究員 (20397821)
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| Project Period (FY) |
2005 – 2006
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| Project Status |
Completed (Fiscal Year 2006)
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| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 2006: ¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 2005: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Keywords | Origin of Solar System / Planetary Formation / Exo-solar Planets / Solar System / Extra-solar Planets / Planetary Cosmogony |
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| Research Abstract |
Detailed models for the density and temperature profiles of gas and dust in protoplanetary disks are constructed by taking into account X-ray and UV irradiation from a central T Tauri star, as well as dust size growth and settling toward the disk midplane. The spatial and size distributions of dust grains are numerically computed by solving the coagulation equation for settling dust particles, with the result that the mass and total surface area of dust grains per unit volume of the gas in the disks are very small, except at the midplane. The H_2 level populations and line emission are calculated using the derived physical structure of the disks. X-ray irradiation is the dominant heating source of the gas in the inner disk and in the surface layer, while the UV heating dominates otherwise. If the central star has strong X-ray and weak UV radiation, the H_2 level populations are controlled by X-ray pumping, and the X-ray-induced transition lines could be observable. If the UV irradiation is strong, the level populations are controlled by thermal collisions or UV pumping, depending on the dust properties. As the dust particles evolve in the disks, the gas temperature at the disk surface drops because the grain photoelectric heating becomes less efficient. This makes the level populations change from LTE to non-LTE distributions, which results in changes to the line ratios. Our results suggest that dust evolution in protoplanetary disks could be observable through the H_2 line ratios. The emission lines are strong from disks irradiated by strong UV and X-rays and possessing small dust grains ; such disks will be good targets in which to observe H_2 emission.
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