#author("2020-10-02T06:56:47+00:00","default:wwwadm","wwwadm")
#author("2020-10-03T05:51:47+00:00","default:wwwadm","wwwadm")
*IoA Seminar 2020 / 令和2年度/2020年度・東京大学・天文学教育研究センター・談話会 [#t8e79eca]

#contents

* Upcoming Seminars [#ebd6a62d]


** No. 359: 8 October 2020 (Thu) 15:30 - 16:30 [#q46a6504]
*** Speaker: Dr. WU, Po-Feng 吳柏鋒 (East Asian Core Observatory Association Fellow) [#ee2536f5]
*** Title: The blind men and the elephant: Multiple evolutionary paths from star-forming galaxies to quiescence [#o9ee6295]

Abstract: 
One of the big unsolved questions in galaxy evolution is how the star-formation activity in galaxies stop and the transformation of morphologies, and how this process and governing mechanisms evolve in cosmic time. 

This talk will focus on z=1 and later, the period that the cosmic star-formation rate density drops rapidly. I will introduce our recent large spectroscopic campaign, the LEGA-C survey, which obtains 3000 ultra-deep optical spectra of galaxies z~1 using 100 nights of the Very Large Telescope. The high-S/N spectra probe the ages and the assembly histories of galaxies through stellar continua. Combing the structural parameters from HST images, I will demonstrate that there is no one simple mechanism that can explain the complex correlation between the formation histories and structures of galaxies. The majority of galaxies likely went through a gentle process that shuts down star-formation slowly without altering the structure, while some galaxies are experiencing rapid change in both star-formation rate and structural at the same time. 

I will further show follow-up studies on post-starburst galaxies, those undergo the rapid decline of star-formation rates, to investigate the driving mechanisms. Various pieces of evidence suggest that post-starburst galaxies had a centrally-concentrated starburst event before the star-formation activity halts. 


Note: we will provide a zoom link, so you can join the seminar remotely. 

** No. 360: 15 October 2020 (Thu) 15:30 - 16:30 [#zb727807]
*** Speaker: NAMEKATA, Kousuke 行方 宏介 (Kyoto University 京都大学) [#n8039b62]
*** Speaker: NAMEKATA, Kosuke 行方 宏介 (Kyoto University 京都大学) [#n8039b62]
*** Title: Stellar superflares on late-type stars - recent results by 3.8-m Seimei telescope - (京大3.8mせいめい望遠鏡で迫る恒星スーパーフレア) [#zd1c2e20]

Abstract: 
Solar flares are explosive phenomena on the solar surface. They often 
produce high XUV radiations, high energy particles, and mass ejections 
which have potential risks to damage human technologies. On other stars, 
such as M dwarfs and young stars, larger ‘superflares’ (more than ten 
times larger than the most energetic solar flares) are known to 
frequently occur, severely affecting the exoplanet habitability. 
Recently, there is an increasing interest in the questions “How do the 
stellar magnetic activities on central stars affect the planetary 
environment?”, and therefore the properties of stellar superflares 
becomes more and more important. Optical spectroscopic observations can 
be a good way to reveal properties of superflares, but the detection has 
been very difficult due to the low occurrence frequency. We have 
conducted optical spectroscopic observations of stellar superflares on 
M-/G-dwarfs with the 3.8-m Seimei telescope since 2019. We have 
succeeded in detecting optical spectra of the rare stellar superflares 
with very high time-cadence and high quality. We found a very dynamic 
change in optical spectra during a superflare as evidence of strong 
injections of high-energy particles to the stellar atmosphere (Namekata 
et al. 2020b). Moreover, we detected the first, conclusive evidence of 
stellar mass ejection, which revealed the mechanism of mass ejection and 
would enable us to estimate its direct impact on exoplanets (Namekata et 
al. submitted). In this talk, I will talk about the recent results by 
the Seimei telescope.
Solar flares are explosive phenomena on the solar surface. They often produce high XUV radiations, high energy particles, and mass ejections which have potential risks to damage human technologies. On other stars, such as M dwarfs and young stars, larger ‘superflares’ (more than ten times larger than the most energetic solar flares) are known to frequently occur, severely affecting the exoplanet habitability. Recently, there is an increasing interest in the question “How do the stellar magnetic activities on central stars affect the planetary environment?”, and therefore the properties of stellar superflares become more and more important. Optical spectroscopic observations have a potential to reveal the properties of superflares, but the detections of ssuperflares have been very rare due to its low occurrence frequency. We have conducted optical spectroscopic observations of stellar superflares on M-/G-dwarfs with the 3.8-m Seimei telescope since 2019. We have succeeded in detecting optical spectra of the rare stellar superflares with very high time-cadence and high quality. We found a very dynamic change in optical spectra during a superflare as evidence of strong injections of high-energy particles to the stellar atmosphere (Namekata et al. 2020b). Moreover, we detected the first, conclusive evidence of stellar mass ejection, which revealed the mechanism of mass ejections and would enable us to estimate its direct impact on exoplanets (Namekata et al. submitted). In this talk, I will talk about the recent results by the Seimei telescope. 




---------------------------------------------------------

* 本談話会について [#c1b638ff]

** 趣旨 [#d48cd456]

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:http://www.ioa.s.u-tokyo.ac.jp/colloquium/wiki/]]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.

**日時 [#ve668db6]
-木曜日
-15:30-16:30

**場所 [#j9cedf34]
-天文センター講義室

**標準タイムテーブル [#b66015f3]
|13:30-14:30|[[院生コロキウム:http://www.ioa.s.u-tokyo.ac.jp/colloquium/wiki/]]|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~|

**世話人 [#q8bd3108]

ML: semiadm _at_ ioa.s.u-tokyo.ac.jp 

please replace _at_ to @

- TANAKA, Masuo 田中培生 mtanaka _at_ ioa.s.u-tokyo.ac.jp 
- MOROKUMA, Tomoki 諸隈智貴 tmorokuma _at_ ioa.s.u-tokyo.ac.jp
- TAKEKOSHI, Tatsuya 竹腰達哉 tatsuya.takekoshi _at_ ioa.s.u-tokyo.ac.jp
- SAMESHIMA, Hiroaki 鮫島寛明 hsameshima _at_ ioa.s.u-tokyo.ac.jp




** Schedule [#ac94b97b]
|BGCOLOR(cyan):#|BGCOLOR(cyan): Date|BGCOLOR(cyan):Speaker|BGCOLOR(cyan):Title|BGCOLOR(cyan):Chair|
|359|2020/10/08(Thu) 15:30 - 16:30 | 吳柏鋒 Wu, Po-Feng (EACOA Fellow/NAOJ) | The blind men and the elephant: Multiple evolutionary paths from star-forming galaxies to quiescence | TT |
|360|2020/10/15(Thu) 15:30 - 16:30 | 行方宏介 Namekata, Kousuke (京都大学) | Stellar superflares on late-type stars - recent results by 3.8-m Seimei telescope  | TM |
|360|2020/10/15(Thu) 15:30 - 16:30 | 行方宏介 Namekata, Kosuke (京都大学) | Stellar superflares on late-type stars - recent results by 3.8-m Seimei telescope  | TM |




**終了した談話会(2019年度) [#h9b1f387]
詳細はこちら: [[平成31(2019)年度談話会]]
|BGCOLOR(cyan):#|BGCOLOR(cyan): Date|BGCOLOR(cyan):Speaker|BGCOLOR(cyan):Title|BGCOLOR(cyan):Chair|
|345|2019/04/01(Mon) 15:30 - 16:30 | J. Xavier Prochaska (UCO/Lick Observatory) | The Wolfe Disk: ALMA Discoveries of Distant, HI-selected Galaxies | KK |
|346|2019/06/27(Thu) 15:30 - 16:30 | Yuu NIINO (IoA/Univ. of Tokyo) | The origin of short and intense explosions in the universe | KK |
|347|2019/07/02(Tue) 16:00 - 17:00 | Wakiko ISHIBASHI (University of Zurich) | How AGN radiative feedback may shape black hole-galaxy co-evolution | KK |
|348|2019/07/04(Thu) 15:30 - 16:30 | Hidenobu YAJIMA (Univ. of Tsukuba) | Cosmological simulations of galaxy formation at the epoch of reionization | KK |
|349|2019/07/11(Thu) 15:30 - 16:30 | Fumihiko USUI (Kobe University) | 近赤外線分光観測による小惑星の含水鉱物探査 | RO |
|350|2019/08/26(Mon.) 15:30 - 16:30 | Glenn Orton (NASA/JPL) | The Exploration of Jupiter by the Juno Mission | RO |
|351|2019/10/2(Wed) 13:15 - 14:15 | 吉田健二 Kenji Yoshida (芝浦工業大学) | Correlations between Optical/Infrared and Gamma-ray Variability in Bright Well-Monitored Blazars 2008-2017 | YN|
|352|2019/10/24(Thu) 15:30 - 16:30 | 橋本哲也 Tetsuya Hashimoto (台湾国立清華大学) | Recent three discoveries from NTHU cosmology group | YN |
|353|2019/10/28(Mon) 13:00 - 14:-0 | Kevin Fogarty (Caltech) | Cooling and Condensation in Cool-Core Galaxy Clusters: the Case of MACS 1931.8-2635 | KK |
|354|2019/10/31(Thu) 15:30 - 16:30 | 徳田一起 Kazuki Tokuda (Osaka Prefecture University) | ALMAによる大小マゼラン雲とM33の巨大分子雲観測 ALMA observations of GMCs in the Large/Small Magellanic Clouds and M33 | KK |
|355|2019/11/07(Thu) 15:30 - 16:30 | 高倉理 Satoru Takakura (IPMU/U.Tokyo) | A measurement of the degree-scale CMB polarization with POLARBEAR | KK  |
|356|2019/11/14(Thu) 14:30 - 15:30 | Ewine van Dishoeck (Leiden Univ.) | Molecules from clouds to disks and planets | KK |
|357|2019/12/05(Thu) 15:30 - 16:30 | 鮫島寛明 Hiroaki Sameshima (IoA/U.Tokyo) | Spectroscopic studies on quasars and stars | YN |
|358|2019/12/12(Thu) 15:30 - 16:30 | 坂野正明 Masaaki Sakano (Wise Babel) | 英語の『数』を考える — 冠詞、単数複数、非可算 | KK |

**これまでの談話会 [#e657f394]
-[[平成31(2019)年度談話会]]
-[[平成30 (2018) 年度談話会]]
-[[平成29 (2017) 年度談話会]]
-[[平成28 (2016) 年度談話会]]
-[[平成27 (2015) 年度談話会]]
-[[平成26 (2014) 年度談話会]]
-[[平成25 (2013) 年度談話会]]
-[[平成24 (2012) 年度談話会]]
-[[平成23 (2011) 年度談話会]]
-[[平成22 (2010) 年度談話会:http://www.ioa.s.u-tokyo.ac.jp/danwakai//past/danwakai_H22.html]]
-[[平成21 (2009) 年度談話会:http://www.ioa.s.u-tokyo.ac.jp/danwakai//past/danwakai_H21.html]]
-[[平成20 (2008) 年度談話会:http://www.ioa.s.u-tokyo.ac.jp/danwakai//past/danwakai_H20.html]]
-[[平成19 (2007) 年度談話会:http://www.ioa.s.u-tokyo.ac.jp/danwakai//past/danwakai_H19.html]]
-[[平成18 (2006) 年度談話会:http://www.ioa.s.u-tokyo.ac.jp/danwakai//past/danwakai_H18.html]]
-[[平成17 (2005) 年度談話会:http://www.ioa.s.u-tokyo.ac.jp/danwakai//past/danwakai_H17.html]]
-[[平成16 (2004) 年度談話会:http://www.ioa.s.u-tokyo.ac.jp/danwakai//past/danwakai_H16.html]]
-[[平成15 (2003) 年度談話会:http://www.ioa.s.u-tokyo.ac.jp/danwakai//past/danwakai_H15.html]]
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