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Abstract: In the Local Group, there are several tens of dwarf galaxies, which have sub-solar metallicity. They provide us a great opportunity to constitute a basic template to study faint low-metallicity galaxies, such as those at high redshift. Because metallicity is an important parameter which significantly affects gas-phase and grain surface chemistry, chemical compositions of molecular clouds in low-metallicity dwarf galaxies are of great interest. To investigate the chemical composition in low-metallicity environments, we have conducted spectral line survey observation in the 3 mm band (85-116 GHz) toward low-metallicity dwarf galaxies, the Large Magellanic Cloud, IC10, and NGC6822. The lines of CCH, HCN, HCO+, HNC, CS, SO, 13CO, and 12CO have been detected. The spectral intensity patterns are found to be similar among three dwarf galaxies. Compared with solar-metallicity environments, the chemical compositions of dwarf galaxies are characterized by deficient nitrogen-bearing molecules, as a direct effect of the lower elemental abundance of nitrogen, and abundant CCH and deficient CH3OH, as an effect of extended photon dominated regions in cloud peripheries due to the lower abundance of dust grains.
Language: TBD
Abstract: Constraining the grain size in protoplanetary disks is a key to understand the first stage of planet formation. The grain size has been estimated by measuring the spectral index at millimeter wavelengths, while it has huge uncertainties. Here, we propose that millimeter-wave polarization is another method to constrain the grain size. We show that thermal dust emission is scattered off of other dust grains and the residual polarization is up to 2.5 %, which is detectable with ALMA. This self-scattering polarization is efficient only if the maximum grain size is comparable to the wavelengths. Therefore, we can constrain the grain size from millimeter-wave polarization of protoplanetary disks. Furthermore, we have observed the protoplanetary disk around HD 142527 with ALMA polarization mode, and found the evidence of the self-scattering plays a role in the protoplanetary disk.
Language: TBD
東京大学・天文学教育研究センターでは2003年4月から, 院生コロキウムに引き続き, 談話会を開いています. 第一線で活躍されている研究者の方々を講師にお招きし, 最先端の研究成果をお話しいただきます. 講師の方には, 大学院生の参加者のことも考慮し, レビュー的な側面も含めた上で, ご自身の研究紹介をお願いしています.
| 13:30-14:30 | 院生コロキウム | 講義室 |
| 15:30-16:30 | 談話会 | 講義室 |
| 16:30- | お茶の時間 | 講義室横のお茶部屋~講師の方を交えて~ |
please replace _at_ to @
| # | Date | Speaker | Title | Chair |
| 301 | 2017/4/13 (Thu) 15:30 - 16:30 | Tao WANG (IoA/U.Tokyo (4月から)) | New insights into the formation of the most massive galaxies at high redshifts | KK |
| 302 | 2017/4/20 (Thu) 15:30 - 16:30 | Matthew W. Johns (U. Arizona) | The Magellan Experience - Building a 6.5 Meter Optical/Infrared Telescope | TT |
| 303 | 2017/4/27 (Thu) 15:30 - 16:30 | 滝脇知也 (国立天文台 理論部) | 重力崩壊型超新星の爆発機構 | MY |
| 304 | 2017/5/11 (Thu) 15:30 - 16:30 | 樫山和己 (東京大学 物理学専攻) | A FRB in a bottle | MY |
| 305 | 2017/5/25 (Thu) 15:30 - 16:30 | 西村優里 (天文学教育研究センター (4月から)) | 低重元素量の矮小銀河における分子雲の化学組成 | KK |
| 306 | 2017/6/1 (Thu) 15:30 - 16:30 | 片岡章雅 (国立天文台フェロー (4月から)) | Millimeter-wave polarization as a tool of investigating the planet formation | KK |
| 307 | 2017/6/15 (Thu) 15:30 - 16:30 | 端山和大 (東京大学 宇宙線研) | TBA | MT |
| 308 | 2017/6/22 (Thu) 15:30 - 16:30 | 福島登志夫 (国立天文台) | 宇宙人存在問題 Question on Alien Civilization Existence | |
| 309 | 2017/7/13 (Thu) 15:30 - 16:30 | Ryan M. Lau (Caltech/JPL) | TBA | KK |
| 310 | 2017/7/20 (Thu) 15:30 - 16:30 | 木坂将大 (青山学院大学) | TBA | MY |
| 311 | 2017/7/27 (Thu) 15:30 - 16:30 | 馬場彩 (東京大学 物理学専攻) | TBA | MY |
詳細はこちら: 平成29 (2017) 年度談話会
| # | Date | Speaker | Title | Chair |
| 301 | 2017/4/13 (Thu) 15:30 - 16:30 | Tao WANG (IoA/U.Tokyo (4月から)) | New insights into the formation of the most massive galaxies at high redshifts | KK |
| 302 | 2017/4/20 (Thu) 15:30 - 16:30 | Matthew W. Johns (U. Arizona) | The Magellan Experience - Building a 6.5 Meter Optical/Infrared Telescope | TT |
| 303 | 2017/4/27 (Thu) 15:30 - 16:30 | 滝脇知也 (国立天文台 理論部) | 重力崩壊型超新星の爆発機構 | MY |
| 304 | 2017/5/11 (Thu) 15:30 - 16:30 | 樫山和己 (東京大学 物理学専攻) | A FRB in a bottle | MY |
