7月10日（火）13:30～14:30 理論コロキウム 講義室
Jul 10 Tue DTA colloquium Lecture-room
7月10日（火）15:00～16:00 太陽系小天体セミナー 南棟２階会議室
Jul 10 Tue Solar System Minor Body Seminar Conference Room, South Bldg.2F
7月11日（水）10:30～12:00 総研大コロキウム 講義室
Jul 11 Wed SOKENDAI colloquium Lecture Room
詳細は以下をご覧下さい。
7月10日（火）
- Campus
- Mitaka
- Seminar
- DTA colloquium
- Regularly Scheduled/Sporadic
- Regularly Scheduled
- Date and time
- July 10, 2018, 13:30-14:30
- Place
- Lecture room
- Speaker
- Riouhei Nakatani
- Affiliation
- University of Tokyo
- Title
- Radiation Hydrodynamics Simulations of Photoevaporation of Protoplanetary Disks: Metallicity Dependence of UV and X-Ray Photoevaporation
- Abstract
- Protoplanetary disks are thought to have lifetimes of several million yr in the solar neighborhood, but recent observations suggest that the disk lifetimes are shorter in a low-metallicity environment. We perform a suite of radiation hydrodynamics simulations of photoevaporating disks with varying the metallicity to study their long-term evolution and the metallicity dependence of mass-loss rates. Our simulations follow hydrodynamics, radiative transfer, and nonequilibrium chemistry in a self-consistent manner. Dust-grain temperatures are also calculated consistently by solving the radiative transfer of the stellar irradiation and grain (re-) emission. In the fiducial case with solar metallicity, including the X-ray effects does not significantly increase the photoevaporation rate when compared to the case with ultra-violet (UV) radiation only. At sub-solar metallicities in the range of Z ? 10^{-1.5} Zsun, the photoevaporation rate increases as metallicity decreases owing to the reduced opacity of the disk medium. The result is consistent with the observational trend that disk lifetimes are shorter in low metallicity environments. Contrastingly, the photoevaporation rate decreases at even lower metallicities of Z ? 10^{-1.5} Zsun, because dust-gas collisional cooling remains efficient compared to far UV photoelectric heating whose efficiency depends on metallicity. The net cooling in the interior of the disk suppresses the photoevaporation. However, adding X-ray radiation significantly increases the photoevaporation rate, especially at Z ~ 10^{-2} Zsun. Although the X-ray radiation itself does not drive strong photoevaporative flows, X-rays penetrate deep into the neutral region in the disk, increase the ionization degree there, and reduce positive charges of grains. Consequently, the effect of photoelectric heating by far UV radiation is strengthened by the X-rays and enhances the disk photoevaporation.
- Facilitator
- -Name：Tomoya Takiwaki
- Comment
- in English
7月10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10日（火曜日）15時～16時
- 場所
- 南棟２階会議室
- 講演者
- 片岡章雅
- 所属
- 理論研究部
- タイトル
- ミリ波偏光観測で探る惑星形成
- Abstract
- 惑星形成の現場である原始惑星系円盤は、特にALMAを中心とした観測
機器の発達により詳細な構造がわかってきた。では、このような円盤内での固体
の合体成長はどのように観測・検証すればよいのか。本講演では、ミリ波偏光観
測を用いた固体の合体成長の観測的検証について理論・観測両面から議論する。 - 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11日（水）
- Campus
- Mitaka
- Seminar
- SOKENDAI colloquium
- Regularly Scheduled/Sporadic
- Regular
- Date and time
- July 11, 2018, 10:30 -12:00
- Place
- Lecture Room
- Speaker
- Misako Tatsuuma
- Affiliation
- University of Tokyo D1(Supervisor: Eiichiro Kokubo,,)
- Title
- Tensile Strength of Porous Dust Aggregates
- Abstract
- (optional)
- Speaker
- Hiroyuki Tako ISHIKAWA
- Affiliation
- SOKENDAI 3rd year (D1)(Supervisor: Tomonori Usuda,Saeko Hayashi,Takayuki Kotani)
- Title
- Review of High-Resolution Near-IR Spectroscopy of M-dwarfs with CARMENES
- Abstract
- I am now attempting to establish the abundance analysis of late-M dwarfs by using Subaru-IRD data. In Europe, the CARMENES group also performs the high-resolution near-infrared spectroscopy on M dwarfs in search of exoplanets. In this talk, I will review the papers written by the CARMENES group, especially those related to the stellar characterization (mainly, V. M. Passegger et al. 2018, A&A).
Please note that the presenter information posted here is not necessarily listed in order of presentation. - Facilitator
- -Name：Yoshiki Hatta
- Comment
- TV conference system is available connecting from Nobeyama, Hawaii, Mizusawa, and Okayama.