国立天文台 セミナー情報 / Seminar Information
国立天文台で翌週に開催されるセミナーの情報をとりまとめ、webとE-mail(semiinfo)でご案内しています。 台内の研究教育活動の情報交換や、台外との研究交流の促進等にご活用ください。 Each week we use this web site and the (semiinfo) email list to announce seminars to be held at NAOJ campuses in the upcoming week. Please inform us of your research and educational meetings so that we can include them.
Solar and Space Plasma (SSP) Seminar
Apr. 10 Mon 15:00-16:30 Solar and Space Plasma Seminar Zoom / Insei Seminar Room (hybrid)
Apr. 11 Tue 10:00-11:30 太陽系小天体セミナー Zoom
Apr. 12 Wed 15:30-17:00 NAOJ Science Colloquium Zoom / the large seminar room (hybrid)
Apr. 14 Fri 16:00-17:00 NAOJ Seminar Zoom / Large Seminar Room (hybrid)
詳細は下記からご覧ください。
“2023.4.10-2023.4.16” の続きを読むFeb. 27 Mon 15:30-17:00 Solar and Space Plasma Seminar Zoom
Feb. 28 Tue 10:00-11:30 太陽系小天体セミナー Zoom
Feb. 28 Tue 16:00-17:00 NAOJ Seminar Zoom/Lecture Room(hybrid)
Mar. 1 Wed 14:30-15:30 ALMA-J Seminar Zoom/ALMA building #102 (hybrid)
Mar. 1 Wed 15:30-17:00 NAOJ Science Colloquium Zoom / Instrument Development Bldg. 3 (hybrid)
詳細は下記からご覧ください。
=============== Feb 27 Mon ===============
Campus： Mitaka
Seminar： Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic： Scheduled
Date and time：2月27日 (月), 15:30-17:00
Place： Zoom
Speaker：永岡賢一
Affiliation：核融合科学研究所
Title：シアがある系の乱流輸送実験研究ートーラスプラズマと電気対流乱流からの話題提供－
Abstract：乱流輸送は自然界に普遍的にみられる現象であるが、その統計的性質は複雑を極め、いくつかの例外を除いて普遍的性質を見いだせていない。磁場閉じ込め核融合プラズマを目指す研究では、乱流中にゾーナルフローと呼ばれるメソスケール構造が自発的に形成され、乱流輸送を大きく制限し、系のダイナミクスにも影響することがわかってきた。最近、我々はこの非線形過程に支配されるゾーナルフローを外部から制御することに挑戦し、磁場の測地曲率により乱流輸送を制御できることを示した。この実験について紹介し、乱流とシアの関係について、議論する。もう一つは、電気対流乱流を用いた実験では、平行平板間を流れる液晶の乱流実験を紹介する。流れを駆動することは、エネルギー注入スケールのシアを系に導入することになるため、その影響を調べることができる。シアによる乱対流の非対称化と乱流による乱流の等方化の競合状態で、双山の速度分布関数のが見つかった。現象論的なモデルにより、乱流、対流、シアの競合状態の結果として、双山の速度分布関数を再現できた。速度分布関数の計測から系の競合状態の診断可能性を指摘した。時間が許せば、対流不安定、対流安定境界に観測される特徴的な輸送現象についても紹介する。
Facilitator
-Name：Takayoshi oba
-Comment：in English
=============== Feb 28 Tue ===============
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：2月28日（火曜日）10時00分～11時30分
場所：zoom
講演者：春日敏測
タイトル：2017年 京都火球と潜在的に危険な地球接近二重小惑星 2003 YT1
Abstract：We present a fireball detected in the night sky over Kyoto,
Japan on UT 2017 April 28 at 15h 58m 19s by the SonotaCo Network. The
absolute visual magnitude is Mv=−4.10±0.42mag. Luminous light curves
obtain a meteoroid mass m=29±1g, corresponding to the size
a_s=2.7±0.1cm. Orbital similarity assessed by D-criterions (cf.
D_SH=0.0079) has identified a likely parent, the binary near-Earth
asteroid (164121) 2003 YT1. The suggested binary formation process is
a YORP-driven rotational disintegration. The asynchronous state
indicates the age of < 1e4yr, near or shorter than the upper limit to
meteoroid stream lifetime. We examine potential dust production
mechanisms for the asteroid, including rotational instability,
resurfacing, impact, photoionization, radiation pressure sweeping,
thermal fracture and sublimation of ice. We find some of them capable of
producing the meteoroid-scale particles. Rotational instability is
presumed to cause mass shedding, in consideration of the recent
precedents, possibly releasing mm-cm scale dust particles. Impacts by
micrometeorites with size≃1mm could be a trigger for ejecting the
cm-sized particles. Radiation pressure can sweep out the mm-sized dust
particles, while not sufficient for the cm-sized. For the other
mechanisms, unprovable or unidentified. The feasibility in the parental
aspect of 2003 YT1 is somewhat reconciled with the fireball observation,
yielding an insight into how we approach potentially hazardous objects.
Kasuga, Sato, Ueda, Fujiwara, Tsuchiya and Watanabe (2020), AJ, 159, 47
https://iopscience.iop.org/article/10.3847/1538-3881/ab4e1b
https://www.nao.ac.jp/news/science/2020/20200115-prc.html
世話人の連絡先
名前：渡部潤一
=============== Feb 28 Tue ===============
Campus：Mitaka
Seminar：NAOJ Seminar
Regularly Scheduled/Sporadic：Sporadic
Date and time：2023 February 28, 16:00-17:00
Place： Zoom/Lecture Room(hybrid)
Speaker:Shi Dai
Affiliation：Western Sydney University
Title：Magnetic Field Reversal around
an Active Fast RadioBurst
Abstract：The environment of actively repeating fast radio bursts (FRBs) has been shown to be complex and varying. The recently localized FRB 20190520B is extremely active, has the largest confirmed host dispersion measure (DM), and is only the second FRB source associated with a compact, persistent radio source (PRS). The main tracer of the magneto-ionic environments is the rotation measure (RM), a path-integral of the line-of-sight component of magnetic field strength (B) and electron density, which does not allow a direct probe of the B-field configuration. Here we report direct evidence for a B-field reversal based on the observed sign change and extreme variation of FRB 20190520B’s RM, which changed from +10000 rad/m^2 to -16000 rad/m^2 between June 2021 and January 2022. Such extreme RM reversal has never been observed before in any FRB nor in any astronomical object. The implied short-term change of the B-field configuration in or around the FRB could be due to the vicinity of massive black holes, a magnetized companion star in binary systems, or a young supernova remnant along the line of sight.
Facilitator
-Name：Fujii, Yuka
=============== Mar 1 Wed ===============
Campus：Mitaka,
Seminar：ALMA-J seminar
Regularly Scheduled/Sporadic： Every Wednesday
Date and time： March 1, 2023 (Wed), 14:30 – 15:30
Place： ALMA building #102 / Zoom (hybrid)
Speaker : Hanae Inami and Hiddo Algera
Affiliation: Hiroshima University and NAOJ/Hiroshima University
Title: An ALMA Systematic Survey of Distant Galaxies: Obscured Star Formation at z~7
Abstract:
In recent years, many massive galaxies have been discovered when the Universe was only 1Gyr old or younger. This raises the question of how so much mass was assembled in such a short time. In particular, some of these galaxies are dust rich, suggesting that dust is also being produced in a rapid manner in the early universe. Taking advantage of ALMA’s capability of efficient spectroscopic searches for galaxies at z > 6.5, we have conducted an ALMA Cycle-7 Large Program, REBELS (Reionization Era Bright Emission Line Survey) to perform a systematic study of the interstellar medium (ISM) in 40 UV-selected galaxies at z > 6.5. The design of this survey has allowed us to spectroscopically confirm 23 galaxies in the Epoch of Reionization, as well as detect dust continuum in 14 galaxies, increasing the number of known dusty galaxies at z > 6.5 by a factor of three. In this talk, we will first present an outline of the REBELS program and then focus on discussing recent results from the dust continuum detections. We will present 1) the typical fraction of obscured star formation in UV-selected galaxies at z~7, and 2) new constraints on the dust-obscured cosmic star formation rate density in the epoch of reionization. In addition, we have conducted follow-up observations with ALMA to cover shorter wavelengths in several REBELS galaxies. We will present recent results on the shape of the infrared spectral energy distribution in three z~7 galaxies, and discuss their dust temperatures, masses and ISM properties in the context of the known high-redshift population.
Facilitator: Shun Ishii, Jorge Zavala
=============== Mar 1 Wed ===============
Campus：Mitaka
Seminar：NAOJ Science Colloquium
Regularly Scheduled/Sporadic：Every Wednesday
Date and time：2023 March 1, 15:30-17:00
Place：zoom / Instrument Development Bldg. 3 (hybrid)
Speaker：Mizutani Yohsuke
Affiliation：NAOJ (M2)
Title：TBD
Abstract：TBD
Speaker：Hatano Shun
Affiliation：NAOJ (M1)
Title：TBD
Abstract：TBD
Facilitator
-Name：Akimasa Kataoka
-Comment：English
Feb. 13 Mon 15:00-16:30 Solar and Space Plasma Seminar Zoom/Central Ridge (North) / 310(hybrid)
Feb. 14 Tue 10:00-11:30 太陽系小天体セミナー Zoom
Feb. 15 Wed 15:30-17:00 NAOJ Science Colloquium Zoom
Feb. 17 Fri 16:00-17:00 NAOJ Seminar Zoom/Large Seminar Room(hybrid)
詳細は下記からご覧ください。
=============== Feb 13 Tue ===============
Campus： Mitaka
Seminar： Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic： Scheduled
Date and time：13th Feb (Mon), 15:00-16:30
Place： hybrid; Central Ridge (North) / 310 or Zoom
Speaker：Andy Shu Ho To
Affiliation：University College London
Title：Coronal Plasma Composition Evolution and Solar Activity
Abstract：Composition of plasma in the solar corona is a tracer of the flow of plasma and energy from the solar interior. A complete understanding of coronal abundances not only provides us another perspective to look at complex processes such as wave propagation, wave absorption, convection, reconnection, and reconfiguration of magnetic fields and coronal heating, but it also has significant implications for solar-like stars. The method to parameterise and study coronal elemental abundances, is to use the first ionisation potential (FIP) bias, defined as taking the ratio of an element’s coronal to photospheric abundance with respect to H. In this seminar, we introduce FIP bias as a proxy to understand processes in different solar structures, ranging from small brightenings to active regions, using a wide range of techniques such as extreme-ultraviolet and radio imaging, and spectroscopy to study to the evolution of these solar structures, and interpret the physical processes underneath.
Facilitator
-Name：Takayoshi oba
-Comment：in English
=============== Feb 14 Wed ===============
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：2月14日（火曜日）10時00分～11時30分
場所：zoom
講演者：紅山仁
所属：東大天文センター
タイトル：微小地球接近小惑星2010 XC15の観測キャンペーン
Abstract：近日点距離が1.3 au 未満の小惑星を地球接近小惑星(Near-Earth Asteroids,
以下NEA)という。NEA
の多くは火星、木星間のメインベルト小惑星が軌道進化した天体であると考えられている。地球の水・生命の起源に関する仮説の中で小惑星による物質輸送は有力な説の一つであり、その検証において
NEA
の軌道進化の解明は必須である。太陽輻射による小天体の軌道進化の度合い(ヤルコフスキ効果の強さ)は天体のサイズや表面状態(アルベド、粒子サイズ分布、ラフネスなど)に依存する。よって
NEA
の軌道進化を明らかにするためには小惑星の表面状態を知る必要がある。一般に空間分解して観測することが難しい小惑星の表面状態の推定例は、小惑星探査機の探査先小惑星を含む極一部に限られる。
2022年12月下旬に微小小惑星2010 XC15(推定直径 100–200
m)が地球に対して地球、月間距離の二倍の距離まで接近した。この期間に NEA である2010
XC15の太陽位相角は60度から100度まで大きく変化した。我々は2010
XC15の幾何アルベド、表面粒子サイズの推定を最大の目的として国内4つの望遠鏡を用いた観測キャンペーン(測光、分光、偏光)を実施した。京都大学岡山天文台のせいめい3.8
m 望遠鏡を用いた測光観測から、2010 XC15の可視スペクトルは太陽に似ており、自転周期は数時間であると推定した。北海道大学の
Pirka 1.5 m 望遠鏡、兵庫県立大学のなゆた2.0 m 望遠鏡を用いた偏光観測から、2010
XC15の偏光度は高位相角でも数パーセントであることがわかった。2010 XC15の低い偏光度は2017年に行われた
Spitzer
宇宙望遠鏡の熱観測に基づく幾何アルベド推定値(~0.35)と整合的である。本講演では測光観測、偏光観測の詳細と現状の結果を紹介する。(微小小惑星の表面状態に関して多くの方に議論していただけますと幸いです。)
世話人の連絡先
名前：渡部潤一
=============== Feb 15 Wed ===============
Campus：Mitaka
Seminar：NAOJ Science Colloquium
Regularly Scheduled/Sporadic：Every Wednesday
Date and time：2023 Feb.15, 15:30-17:00
Place：zoom
Speaker：Nishigaki Moka
Affiliation：NAOJ (M2)
Title：Early Galaxy Formation Near and Far Probed with SDSS and JWST Data
Abstract：Extremely metal poor galaxies (EMPGs), which are defined by the gas-phase metallicity of < 0.1 Zsun, are important to understand the early phase of galaxy formation. Although EMPGs are actively investigated over decades, there are no EMPGs with metallicities below < 0.01 Zsun found so far, which is called the metallicity floor. In addition, the physical origin of EMPGs in the local universe are not fully understood. We search for the metal-poor galaxy candidates in the local universe below the known possible metallicity floor of < 0.01 Zsun, selecting photometric candidates by broadband color excess and machine-learning techniques with the SDSS photometric data. We remove stellar contaminants from the photometric candidates by shallow spectroscopy with Seimei and Nayuta telescopes. We then conduct deep spectroscopy with Magellan/MagE for faint [OIII]4363 lines and confirm that three candidates are EMPGs with 0.05-0.1 Zsun. We also discuss the physical origin of EMPGs from their clustering and chemical properties. Extending the broadband color excess technique to a high-z EMPG search, we select 17 candidates of z ~ 4–5 EMPGs with the deep near-infrared JWST/NIRCam images obtained by Early Release Observations (ERO) and Early Release Science (ERS) programs. We find galaxy candidates with negligible [OIII]4959,5007 emission weaker than the local EMPGs and known high-z galaxies, suggesting that some of these candidates may fall in 0–0.01 Zsun, which potentially break the lowest metallicity limit known to date.
Speaker：Watanabe Kuria
Affiliation：NAOJ (M1)
Title：Elemental Abundance Ratios and Origin of Very High (Fe/O) in Extremely Metal-Poor Galaxies
Abstract：Extreme metal-poor galaxies (EMPGs) are low metallicity, and young.
Elemental abundance ratios of EMPGs provide insight into star formation in the early stages of galaxy formation. Although the metallicity of EMPGs is less than 10 % of solar, several EMPGs with [Fe/O] as large as the solar abundance are reported.
Since EMPG is a young galaxy, type Ia supernovae have probably not yet occurred.
Therefore, we investigate the possibility that pair-instability supernovae (PISN) and hypernovae (HN) with high explosion energy produced rich iron. Using our initial mass function and the yields of previous studies, we develop the models of the chemical evolution of galaxies and compare them to observations. We focus on S and Ar, which are abundant in PISN. Since the [S/O] and [Ar/O] in EMPG are smaller than in the PISN model, we suggest that the origin of Fe in EMPG is not PISN.
We also study the effects of the supernova explosion energy and the mixing & fallback model (Umeda & Nomoto 2002). We calculate the yields of CCSN and HN using the yield calculation code for the core-collapse supernova (CCSN) model. Using the yield with varying effects of the mixing & fallback model, we develop a model of the chemical evolution of galaxies and introduce the results compared to observations.
Facilitator
-Name：Akimasa Kataoka
=============== Feb 10 Fri ===============
Campus：Mitaka
Seminar：NAOJ Seminar
Regularly Scheduled/Sporadic：Regular
Date and time：2023 February 17, 16:00-17:00
Place： Zoom/Large Seminar Room(hybrid)
Speaker：木内 等/ Hitoshi Kiuchi
Affiliation：NAOJ
Title：電波干渉計研究への誘い～VLBI黎明期からALMA, ngVLAへ ～
Abstract：私の研究はNICTでの“黎明期にあった日本のVLBIシステムの研究開発”から始まり、NAOJでの“国際プロジェクトとしてのALMAシステムの研究開発”へと続いてまいりました。同じ電波干渉計技術を用いつつも、NICTではアンテナ間の基線ベクトルの変化測定が主要なテーマであり、NAOJでは電波源の構造測定が主要なテーマでした。電波干渉計の研究開発を始めた頃、技術資料を見て鳥肌が立ったことを覚えています。これまで行ってきたシステム開発および応用技術の開発を中心に電波干渉計技術開発の面白味をご紹介したいと思います。
電波干渉計技術は多分野の技術の集大成であるため、高精度化に必要な多分野間にまたがる沢山の課題をまだまだ見つけることができます。
現在進行中のngVLAへのNAOJ独自技術での貢献の可能性についてもご報告致します。
Facilitator
-Name：Fujii, Yuka
Jan. 23 Mon 14:00-16:00 SOKENDAI Doctoral Thesis Defense Zoom
Jan. 23 Mon 15:00-17:00 Solar and Space Plasma Seminar Zoom/Insei Seminar Room(hybrid)
Jan. 24 Tue 10:00-11:30 太陽系小天体セミナー Zoom
Jan. 25 Wed 10:00-12:00 SOKENDAI Colloquium Zoom
Jan. 25 Wed 14:30-15:30 ALMA-J seminar Zoom
Jan. 25 Wed 15:30-17:00 NAOJ Science Colloquium Zoom
Jan. 27 Fri 13:30-15:00 Solar and Space Plasma Seminar Zoom/Insei Seminar Room(hybrid)
詳細は下記からご覧ください。
“2023.1.23-2023.1.29” の続きを読む詳細は以下をご覧下さい
“2022.12.12-2022.12.18” の続きを読む