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The Subaru Seminar is usually held in Room 104 of the Hilo Base Facility, adjacent to the main lobby. Everyone is welcome to attend. If you are interested in giving a seminar, please contact Subaru seminar organizers (Tomonori Usuda, Kumiko S. Usuda, Masayuki Akiyama) by email : (please change"_at" to @).

November 26, Monday at 11:00 am

" Molecular Hydrogen Emission from Protoplanetary Disks "

Hideko Nomura (Queen's University, UK)

Thanks to recent high spectral resolution and high sensitivity observations, it has become possible to detect molecular hydrogen line emission from protoplanetary disks. Now, it is believed that in the disks dust particles stick each other and grow in size, as well as settle towards the disk midplane. As these processes are thought to be the first step of planet formation, it is of great interest to find observational evidence of the dust evolution in the disk.
In this work we have constructed a detailed disk model, taking into account heating of gas and dust via irradiation from a central star, as well as the dust coagulation and settling in the disk. In addition, we have calculated the level populations of molecular hydrogen and the line emission from the disk. Our results show that as the dust particles evolve in the disks, the gas temperature at the disk surface drops because of inefficient grain photoelectric heating, which leads to a change in the dominant H2 excitation mechanism from thermal to UV fluorescent. Therefore, our model calculations suggest that the dust evolution in protoplanetary disks could be observable through the H2 line ratios.

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