7月21日（火）13：30～15：00 太陽系小天体セミナー zoom
Jul 21 Tue Solar System Minor Body Seminar
7月21日（火）15：00～17：00 Final Defense for the doctoral thesis of the Department of Astronomical Science, SOKENDAI
Jul 21 Tue zoom
7月22日（水）13：30～15：00 NAOJ Science Colloquium zoom
Jul 22 Wed
7月22日（水）15：00～16：00 ALMA-J seminar zoom
Jul 22 Wed
Jul 22 Wed
詳細は以下をご覧下さい。
7月21日（火）
- キャンパス
- 三鷹
- セミナー名
- 太陽系小天体セミナー
- 定例・臨時の別
- 定例
- 日時
- 7月21日（火曜日）13時30分～15時
- 場所
- zoom
- 講演者
- 匠あさみ
- 連絡先
- 名前：渡部潤一
- 備考
- テレビ会議またはスカイプによる参加も可
7月21日（火）
- Campus
- Mitaka
- Seminar
- Final Defense for the doctoral thesis of the Department of Astronomical Science, SOKENDAI
- Regularly Scheduled/Sporadic
- Sporadic
- Date and time
- 21 July, 15:00～17:00
- Place
- Mitaka seminar room and Zoom
- Speaker
- Yuhang Zhao
- Affiliation
- Department of Astronomical Science, The Graduate University for Advanced Studies, SOKENDAI
- Title
- Development of a frequency dependent squeezed vacuum source for broadband quantum noise reduction in advanced gravitational-wave detectors
- Facilitator
- -Name：Graduate Student Affairs Unit, Research Promotion Group
7月22日（水）
- Campus
- Mitaka
- Seminar
- NAOJ Science Colloquium
- Regularly Scheduled/Sporadic
- Every Wednesday
- Date
- 2020 July 22
- Time
- 13:30-15:00
- Place
- Zoom
- Speaker
- Carol Kwok (Univ. of Tokyo, *Student talk)
- Title
- Planetesimal dynamics in the presence of a giant planet
- Abstract
- The standard models of planet formation describe how planets form in axisymmetric, unperturbed disks in single star systems. When there is a massive companion perturbing the disk while planetary bodies start to form, however, the story might alter. For example, it is possible that giant planets could have already formed when other planetary embryos start to grow. In this case, the early evolution of planetesimals can be affected by strong perturbations from the massive planets in the system, an d thus deviate from the standard scenario. Using N-body simulations, we investigate the dynamics of planetesimals, including the distribution an d evolution of their orbital elements, in a system with the presence of nebular gas an d a giant planet perturber at 5.2 AU. We aim at finding out the impact of the perturber on the formation of giant planet cores exterior to the orbit of the perturber. While confirming the results from Kortenkamp & Wetherill (2000), who studied the effect of the perturbation on the orbits of planetesimals interior to the perturber, we find that the orbits of particles distributed in ? 9 ? 15 AU, except for the MMR locations, are generally aligned, an d the typical velocity dispersions of identical-mass particles are on the order of ? 10 m/s in this disk region. As a follow-up of our previous work on the same topic, we narrowed the mass range of particles in order to minimize the effect of self-gravity of planetesimals. Meanwhile, we performed the simulations on a much longer timescale to cover the effect of gas drag on particles with larger masses. With long enough time (t >~ tau_gas), the particles of neighboring mass on the larger end on the mass spectrum become better aligned, resulting in lower encounter velocities among them. Within a reasonable degree of approximation and uncertainty, our results show that the dynamical features of planetesimals displayed in certain parts of the disk makes them ”accretion-friendly” regions where planetary growth is accelerated.
Read more - Facilitator
- -Name：Akimasa Kataoka
7月22日（水）
- Campus
- Mitaka
- Seminar
- ALMA-J seminar
- Regularly Scheduled/Sporadic
- Every Wednesday
- Date and Time
- 2020 July 22 15:00-16:00
- Place
- Zoom
- Speaker
- SORAHANA, Satoko
- Affiliation
- ALMA project, NAOJ
- Title
- Study of brown dwarf atmospheres using near-infrared data
- Abstract
-
I would like to introduce a part of my research on brown dwarfs using near-infrared data in this seminar.
Brown dwarfs are objects of intermediate mass and temperature between stars and planets. The brown dwarf atmospheres are dominated by molecules and dust, which is composed of heavy elements. Therefore, the spectra characterized by the molecules and the dust are very complex and difficult to understand. Previous studies have shown that existing static atmospheric model, which is assuming local thermodynamical equilibrium and solar element abundances, do not fully explain the observed spectrum. In contrast, we have investigated the possibility of deviations of elemental abundances from the solar composition and atmospheric structure out of radiative-convective equilibrium. By incorporating them into the atmospheric model, UCM, we have been able to better reproduce the observed spectra of several brown dwarfs. On the other hand, it was found that there are some objects that cannot be reproduced. In our current study, we focus on the size of the heavy element dusts (iron, MgSiO3, Al2O3), and investigate the dependence of dust size on atmospheric structure (temperature-pressure structure) and spectral shape. As a result, we find that the difference in the opacity of the dust size causes a change in the atmospheric structure and the observed spectra of some objects are better explained by models with larger dust sizes than those we have applied so far. On the other hand, there are some objects whose observational spectra cannot be explained even with model with a large dust size.
If time allows, I would like to introduce my other research on the exploration of brown dwarfs and their distribution in the Galaxy using HSC data also. - Facilitator
- -name: Masumi Shimojo