(Fridays, 16:00 - 17:00)
・理学研究科4号館 5階  504号室(宇宙物理学教室講義室)にて
   (Room 504 [5F], Department of Astronomy [Science, Bldg 4] )


Colloquium 2018.4-2019.3, Dept Astronomy, Kyoto University 世話人 Host: Dr. Herman Lee (email: herman_at_kusastro.kyoto-u.ac.jp) 第568回 題目Title:Recent progress of Space Science and Technology Development in Indonesia 講師Speaker:Dr. Thomas Djamaluddin, Chairman of LAPAN(インドネシア国立航空宇宙研究所の所長) 日時: 7月19日(木)午前10時30分-11時30分 Date: Thursday, July 19th, 2018 starting at 10:30 a.m. 場所: 理学研究科4号館 5階 504号室 Place: Room 504 in the Faculty of Science Bldg. No.4 言語:  英語   Language: English 概要Abstract: I will introduce LAPAN activities in developing space science and technology (satellite, rocket, aeronautics, remote sensing, atmospheric science, and space environment studies, including astronomy). The main purpose of my visit this time is to discuss future research collaboration between LAPAN and Kyoto University on the field of astronomy. LAPAN-Kyoto Univ collaboration so far in the field of atmospheric science. 第567回 題目Title:Formation of Massive Black Hole Seed via Direct Collapse: cosmological zoom-in hydro simulation with radiation transfer 講師Speaker: 長峯 健太郎 氏 (大阪大学) 日時: 7月12日(木)午後3時30分 Date: Thursday, July 12th, 2018 starting at 15:30 p.m. 場所: 理学研究科4号館 5階 504号室 Place: Room 504 in the Faculty of Science Bldg. No.4 言語:  英語   Language: English 概要Abstract: Direct collapse of a gas sphere is an attractive scenario for the formation of massive black hole seed. We model collapse of a primordial gas within dark matter halos using high-resolution cosmological zoom-in hydro simulations with flux-limited diffusion (FLD) approximation for radiation transfer. Collapse is followed down to the formation of photosphere, and adiabatic models have been run for comparison. We find that (1) the FLD flow forms an irregular central structure with dynamically insignificant rotation, and does not exhibit fragmentation. This is contrary to adiabatic model which forms an asymmetric, geometrically-thick disk that drives a pair of strong spiral shocks, subject to Kelvin-Helmholtz shear instability, forming fragments; (2) the growing central core in the FLD flow quickly reaches a core mass of ~10 Msun and a highly variable luminosity of order of 10^38-10^39 erg/s, comparable to the Eddington luminosity. It experiences massive recurrent outflows driven by radiation force and thermal pressure gradients, which form dense expanding shells, mixing with the accretion flow and transferring the angular momentum outwards; and (3) the interplay between radiation and thermal pressure gradients and gravity, subject to the massive accretion rate, results in photosphere of radius ~10 AU, much larger than that of a protostar. Overall, the inclusion of radiative transfer reveals complex early stages of formation and growth of the central structure in direct collapse scenario of massive black hole formation. For more details, please see arXiv:1803.03278 and 1801.08545. 第566回(水曜雑誌会 兼) 題目Title: ALMA高解像観測で調べるAGNトーラスの構造と物理的起源 講師Speaker:泉 拓磨 (国立天文台 ハワイ観測所) 日時:6月13日(水)13:30 - 14:30 Date: 13th June (Weds) 13:30 - 14:30 場所:理学研究科4号館 5階会議室 Venue: 5/F Conference Room, Building 4, Faculty of Science 概要Abstract: 「超巨大ブラックホールへの質量降着により輝く活動銀河中心核(Active Galactic Nucleus = AGN)は、その周囲をドーナッツ状のガス・ダスト成分(トーラス)が取り囲んでいる。しかるに可視光帯における輝線 の"見え方"が見込み角に依存して変化するのだ!」というのが、30年以上にわたるトーラスパラダイムの基本理念であり、 多くの観測がこれを支持してきた。しかし最近では、この古典的描像では説明できない現象も報告され始めており、 以前にも増して、(1) いかにしてそのドーナッツ形状 = 幾何学的に厚い構造を形成・維持するのか? (2) 詳細なトーラスの内部構造はどうなっているのか?といった基本問題の解決が望まれている。 こうした背景を念頭に、我々は、ALMAを用いたトーラス領域のガス・ダスト分布の探査を推進している。本講演では、 最近傍AGNであるCircinus銀河の中心部における、COガスとCIガス輝線、ならびにダスト連続波の~5-10 pc分解能の観測結果を紹介する。本研究では特に、トーラスは分子・原子といったガスの相に応じて異なる内部構造を 持っており、その構造・力学は、近年注目されている「輻射駆動型噴水モデル」でよく説明できることが分かった。 これは、「トーラスとはAGN近傍のインフローやアウトフローが織り成した"実効的にドーナッツ状に見える"構造である」 という意見を支持しており、トーラスの物理的起源に迫る成果だと期待される。 第565回 題目Title: 火星と宇宙生物学 講師Speaker:丸山 茂徳 (東京工業大学地球生命研究所) 日時:6月8日(金)15:00 - 16:00 Date: 8th June (Fri) 15:00 - 16:00 場所:理学研究科4号館 5階会議室 Venue: 5/F Conference Room, Building 4, Faculty of Science 概要Abstract: これまでの火星の研究を振り返るとともに、火星における 生命の可能性を議論する。さらに、次の系外惑星探査のゴールに 向けて、宇宙生物学の最前線を開拓する。 (参考文献: 火星の生命と大地46億年(講談社、2008年)) 第564回 題目Title: 日本における低周波電波天文学の可能性 -MUレーダー受信部などを例にして- 講師Speaker:Dr. Toshio Terasawa 寺澤 敏夫 (NAOJ 水沢VLBIグループ) 日時:5月25日(金)15:00 - 16:00 Date: 25th May (Fri) 15:00 - 16:00 場所:理学研究科4号館 5階会議室 Venue: 5/F Conference Room, Building 4, Faculty of Science 概要Abstract: 最近、瞬発電波バースト(Fast Radio Bursts=FRB)や、 赤方偏移〜17付近での中性水素21cm線吸収の発見など、 周波数が数GHz以下での低周波電波天文学の話題が賑やかです。 そのような世界的な潮流の中で、日本でできることは何か、 いくつかの具体例を通して考えてみたいと思います。例えば、 ・京大MUレーダー受信部を用いた45MHz全天マップ(前田ほか、2011) ・鹿島、臼田、飯館、豊川などのアンテナ群によるCrabパルサー観測(三上ほか、2016) など。 第563回 題目Title: Letting the Data Speak for Themselves: What Observations Tell Us About Galaxy Formation 講師Speaker:Prof. Neal Katz (U. Mass Amherst) 日時:4月20日(金)16:00 - 17:00 Date: 20th April (Fri) 16:00 - 17:00 場所:理学研究科4号館 5階会議室 Venue: 5/F Conference Room, Building 4, Faculty of Science 概要Abstract: We infer the star formation rates in dark matter halos at different redshifts from halo merger histories expected in a Lambda CDM cosmology using Bayesian inference and Bayes ratios to restrict the model complexity, constrained to match the observed stellar mass/luminosity functions of galaxies at different redshifts and the local cluster galaxy luminosity function, which has a steeper faint end than that of field galaxies. The only other assumptions that we make are that the star formation rate of central galaxies depends on the halo mass and redshift and that when a galaxy becomes a satellite its star formation rate is quenched exponentially and it can eventually merge with the central galaxy on a dynamical friction timescale. We find that 1) the star formation in the central galaxies of high mass halos (>10e12) has to be boosted at high redshift beyond what is expected from a simple scaling of the dynamical time; 2) below z=2 the star formation in halos below 1e11 must be quenched, which is not directly expected in standard stellar feedback models and is most easily explained by some form of preheating, and implies that there is a significant old stellar population in present-day dwarf galaxies with M_star < 10e8 and steep slopes for the high redshift stellar mass and star formation rate functions 3) the stellar mass of galaxies assembles in one of three ways depending on halo mass: > 1e12 the galaxies assemble through mergers and should hence have a spheroidal morphology and between 1e11 and 1e12 (e.g MW) it assembles slowly and at z>2 has less than 5% of its mass in place, which has extreme observational consequences. <<<以下 平成29年度>>> 第562回 題目Title: Exploring the super-Eddington accretion around compact objects 講師Speaker:Dr. Chin-Ping Hu (University of Hong Kong) 日時:03月20日(火)16:00 - 17:00 Date: 20th Mar (Tues) 16:00 - 17:00 場所:理学研究科4号館 5階会議室 Venue: 5/F Conference Room, Building 4, Faculty of Science 概要Abstract: Galactic black holes (BHs) are strong X-ray emitters through accretion and their luminosities are constrained by the Eddington limit. On the other hand, most ultraluminous X-ray sources (ULXs) in external galaxies are powered by stellar-mass BHs with super-Eddington accretion rates and they show distinct spectral behaviors from canonical spectral states of BH X-ray binaries (BHXBs). It was proposed that the ULX is an unusual evolutionary phase of high-mass X-ray binaries. A low-mass X-ray binary showing sub-Eddington outbursts is possible to evolve into a ULX with a long-lived ultraluminous outburst although the link remains unclear. Recently, a transient ULX exhibiting both a canonical soft X-ray transient outburst and an ultraluminous outburst was found. It provides an important sample that contains most fruitful spectral states and bridge the BHXBs and ULXs. Except for BHs, a non-negligible portion of ULXs have been confirmed to harbor accreting neutron stars (NSs). They challenged the magnetospheric accretion of NSs and are probably accreting magnetars. However, their companions are likely Roche-lobe filled early-type stars and the super-critical accretion is a possible scenario. I will discuss the recent discoveries, theoretical interpretations, and future prospects about these extreme compact objects. 第561回 題目Title:Fiber-based heterodyne infrared interferometer: Towards a small proof-of-principle prototype at 1.55 μm 講師Speaker:Prof. Ernest A. Michael (Astro-Photonics Laboratory, RAIG, University of Chile) 日時:02月08日(木)16:00 - 17:00 Date: 08th Feb (Thu) 16:00 - 17:00 場所:理学研究科4号館 5階会議室 Venue: 5/F Conference Room, Building 4, Faculty of Science 概要Abstract: I present the concept for a relatively low-cost near-infrared heterodyne interferometer based on commercial 1.55μm fiber components. First lab results were obtained for the telescope to single-mode fiber coupling control, LO phase-stabilization between both telescopes, and the heterodyne correlation receiver system, and an on-sky demonstration is planned with our 14”-telescopes. I discuss the applicability of this concept for long-baseline, high telescope number systems and mid-infrared wavelengths. 第560回 題目Title:A Unified Model for Tidal Disruption Events 講師Speaker:Prof. Lixin (Jane) Dai (Niels Bohr Institute, University of Copenhagen) 日時:11月24日(金)16:00 - 17:00 Date: 24th Nov (Fri) 16:00 - 17:00 場所:理学研究科4号館 5階会議室 Venue: 5/F Conference Room, Building 4, Faculty of Science 概要Abstract: In the centers of galaxies, scatterings between stars can kick a star into a fatal trajectory around the central supermassive black hole. The star approaches the black hole so closely that large tidal force can tear apart the star, and eventually half of the star is accreted onto the black hole producing a very luminous flare. This is called a tidal disruption event (TDE). Only in the past few years wide-field transient surveys have allowed us to get photometric and spectroscopic data on multiple candidate events. The recent breakthrough in TDE observations however have shone a spotlight on our incomplete theoretical understanding. While the physical processes in TDEs are universal, some observed TDEs radiated in thermal X-ray while others radiated in UV and optical. Moreover, only a small fraction of TDEs produced relativistic jets. The key theoretical component lacking so far in TDE studies is how the accretion and emission physics should be different from standard accretion scenarios, because in TDEs stellar debris is fed to the black hole at a rate beyond the Eddington limit. I utilize state-of-the-art three-dimensional general relativistic radiation magneto hydrodynamics simulations to study the physics of this extremely dense, hot and luminous accretion. Besides showing general properties of super-Eddington accretion disks, outflows and jets, in this talk I will focus on showing how the viewing angle dependence of this accretion disk can provide a unification model for different classes of TDEs. 第559回 題目Title:ブレーザー天体の可視偏光観測 講師Speaker:Prof. Makoto Uemura (Hiroshima University) 日時:11月21日(火)15:30 - 17:00 Date: 21st Nov (Tues) 15:30 - 17:00 場所:理学研究科4号館 5階会議室 Venue: 5/F Conference Room, Building 4, Faculty of Science 概要Abstract: ブレーザーは活動銀河核のジェットが観測者方向を向いており、ビーミング効果 によってジェットからの放射が卓越している天体である。時間変動のタイムスケール も短くなることから、ブレーザーはジェットの研究に適した天体とされる。偏光観測 はジェット中の磁場の情報を与えてくれる貴重な観測手法であるため、多波長観測と 共に、ブレーザー研究では注目されてきた。一方で、その時間変動の多くは不規則な 変動であり、ジェットの普遍的な特徴を抽出するのは容易でない。広島大学「かなた 望遠鏡」はフェルミγ線宇宙望遠鏡との共同研究で、2007年よりブレーザーの偏光 観測を行ってきた。我々の観測データは観測頻度・継続期間・天体数において前例の ないものとなっており、その中で注目すべき偏光方位角の回転現象が複数捉えられて いる。本講演では偏光方位角の特性・時間変化からブレーザージェットにどのような 知見が得られるのか、かなた望遠鏡の結果を中心に最近の研究をレビューする。 ーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーー 第557回 第558回(ダブルヘッダー、ご注意を!) ーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーーー (1) 題目Title:Development and Initial Operations of the NICER Mission 講師Speaker:Dr. Keith Gendreau (NASA Goddard Space Flight Center) 日時:10月6日(金)15:00 - 16:00 Date: 6th June (Fri) 15:00 - 16:00 場所:理学研究科4号館 5階会議室 Venue: 5/F Conference Room, Building 4, Faculty of Science 概要Abstract: The Neutron Star Interior Composition Explorer (NICER) is a NASA mission of opportunity on the International Space Station (ISS) that is dedicated to the study of neutron stars and X-ray transients. NICER provides an order of magnitude improvement in timing resolution, energy resolution, and sensitivity compared to the last X-ray timing mission flown. NICER was successfully launch on June 3, 2017 and is conducting its science program. I will discuss the development of the NICER mission and some of the challenges and benefits of being an ISS payload. I will also discuss initial performance and some of the first science results of NICER. (2) 題目Title:Strong Gravitational Lensing as a Probe of Galaxy Evolution and Cosmology 講師Speaker:Dr. Kenneth Wong (EACOA Fellow, ASIAA/NAOJ) 日時:10月6日(金)16:00 - 17:00 Date: 6th June (Fri) 16:00 - 17:00 場所:理学研究科4号館 5階会議室 Venue: 5/F Conference Room, Building 4, Faculty of Science 概要Abstract: Strong gravitational lensing is a powerful probe of the mass distribution in the Universe. Lensing is sensitive to the total mass distribution along the line of sight, making it a unique probe of dark matter in lensing galaxies. However, strong lenses are quite rare and require deep wide-area imaging surveys to build up a statistical sample. The Hyper-Suprime Cam survey is an ongoing multiband imaging survey using the Subaru Telescope that will cover 1400 deg^2 of the sky to a depth of r~26. I present the current progress of the survey and the various projects within the HSC SSP strong lens working group, which are focused on both discovering new lenses and leveraging these systems for studies of galaxy structure and cosmology. Searches for lensed quasars are particularly valuable because they are variable and can be monitored to measure the "time delay" between the multiple images. In particular, the time-delay distance from such a system is primarily sensitive to the Hubble constant (H0) that is key to probing dark energy, neutrino physics, and the spatial curvature of the Universe, as well as discovering new physics. I discuss the H0 Lenses In COSMOGRAIL’s Wellspring (H0LiCOW) project, which aims to measure H0 to <3.5% precision from five lensed quasars using deep Hubble Space Telescope imaging, precise time delay measurements, a measurement of the velocity dispersion of the lens galaxies, and a characterization of the mass distribution along the line of sight. The most recent H0LiCOW analysis of the system HE 0435-1223 is able to constrain the time-delay distance to a precision of ~8%. In combination with the previous two H0LiCOW lenses, we constrain H0 to ~3.8% precision for a flat Lambda CDM cosmology. These results are consistent with independent determinations of H0 using the distance ladder method and are in moderate tension with the latest Planck results for a similar cosmology, hinting at possible new physics beyond the standard LCDM model and highlighting the importance of this independent probe. 第556回 題目Title:Cosmic gamma-ray lines: observations, lessons, and puzzles 講師Speaker:Prof. Roland Diehl (MPE and Excellence Cluster 'Universe') 日時:9月5日(火)15:30 - 17:00 Date: 5th Sep (Tues) 15:30 - 17:00 場所:理学研究科4号館 5階会議室 Venue: 5/F Conference Room, Building 4, Faculty of Science 概要Abstract: Cosmic gamma-ray lines are messengers of transitions in high-energy systems, and complement astrophysics based on realms of atomic and thermal physics and processes. In the low-energy part of gamma rays, nuclei and their energy levels dominate the observable signatures; we will include electron-positron annihilation in addition, as one case of the astro-particle processes that dominate physics in the high-energy part of the gamma-ray regime. Astronomical observations of nuclear transitions show that cosmic nucleosynthesis produces unstable radioactive isotopes: The gamma rays seen from decays of 56Ni, 44Ti, 60Fe, and 26Al thus have spawned studies of supernovae and massive-star interiors, where cosmic nuclear reactions produce these isotopes. Supernova explosions in their interiors appear to be clearly driven by processes that are intrinsically not spherically symmetric, confirming insight as obtained from developments in theoretical and numerical models of supernova explosions. The long-lived radio-isotopes (60Fe, 26Al) decay far from their sources, and cumulative emission from many sources tells us about interstellar transport of nucleosynthesis ejecta. The time scale addressed here is millions of years, and fills an observational gap between supernova remnants and matter recycled between stellar generations. We will illuminate here what chemical evolution models often abbreviate as instantaneous recycling, and discuss the role of large interstellar cavities called superbubbles. Interstellar annihilation of positrons produces the brightest gamma-ray line in this regime, at 511 keV. We will discuss the diversity of candidate sources of such positrons. We show that most of those cannot explain what gamma-ray telescopes measure, and single dominating sources as often claimed are rather not the solution; astroparticle studies from multiple messengers seem a promising strategy. 第555回 題目Title:ペルーでの天文学の状況 講師Speaker:イシツカ・ホセ(ペルー地球物理研究所) 日時:9月1日(金)16:00 - 17:00 Date: 1st Sep (Fri) 16:00 - 17:00 場所:理学研究科4号館 5階会議室 Venue: 5/F Conference Room, Building 4, Faculty of Science 概要Abstract: 60年前父の石塚睦がペルーへ渡り太陽の観測を充実し太陽コロナ観測所を作り上げた。コスモスコロナ観測所はペルー のアンデス山脈上の海抜4、600メートルの所に建てられたが太陽のコロナの観測が出来てから数週間後に観測所は テログループに占領された後コロナグラフはダイナマイトで爆発された。父はその後テログループから死の宣告の手紙を 受けリマへ潜伏した。ペルー政府に寄りテロ活動を治めることが出来た後父はペルーでの天文学の定着活動を始めた結果 ペルー地球物理研究所の新本部にペルー国立プラネタリュームを設置が出来た、そしてリマの南の街イカにてイカ国立大学 に太陽観測所を設置が完成した直後京都大学の飛騨天文台の太陽フレアー望遠鏡を移動して2010年から継続して太陽 の活動の観測が出来ています。私は2006年からペルー地球物理研究所で働くことが出来て父の仕事の手伝いをして 来ましたがメインの仕事は衛星通信用のアンテナを電波望遠鏡に改造することでした。ところで去年の政府交代により ペルー地球物理研究所の所長と副所長は変わり今年に入り父がして来たこと、私がして来たことを全て認めずの状況です、 発表では今の状況の詳細を説明します。 第554回 題目Title:Prominent Extended Narrow Fe Ka Emission in Nearby AGN 講師Speaker:Prof. Franz Bauer (Pontifical Catholic University of Chile) 日時:7月11日(火)13:30 - 15:00 Date: 11th July (Tues) 13:30 - 15:00 場所:理学研究科4号館 5階会議室 Venue: 5/F Conference Room, Building 4, Faculty of Science 概要Abstract: X-ray studies of Active Galactic Nuclei have helped piece together a rough outline of the inner structure around accreting supermassive black holes via spectral and temporal decomposition of the various components contributing to the X-ray spectrum. Intriguingly, Chandra has now built up relatively deep exposures for many famous nearby obscured AGN, sufficient to examine spatially extended contributions. We make Fe Ka equivalent width images and find that, after modeling the nuclear PSF and removing it, substantial extended (>1") Fe Ka emission remains around many well-known AGN. I will present radial profiles and morphologies of the Fe Ka excesses, and argue that a significant (possibly dominant) fraction of the Fe Ka lines in AGN arise from reflection off material well outside of the fiducial "torus" region. These results offer interesting potential for future resolved X-ray line studies, as well as guidance for the modeling and interpretation of poor signal-to-noise and unresolved X-ray spectra of AGN. 第553回 題目Title:形成途上にある銀河・銀河団の研究のハイライトと将来展望 講師Speaker:児玉 忠恭 教授 (東北大学) Prof. Tadayuki Kodama (Tohoku Univ.) 日時:6月28日(水)15:30 - 17:00 Date: 28th June (Weds) 15:30 - 17:00 場所:理学研究科4号館 5階会議室 概要Abstract: 赤方偏移が1から3の時代は宇宙において最も星形成活動が活発な時代であった。 銀河団も活発に集団化しており、楕円銀河の祖先が急速に成長した時代でもある。 従ってこの時代の銀河、銀河団の性質を詳しく調べることは極めて重要である。 我々はすばる望遠鏡の広視野観測能力を活用して、特に遠方銀河団の観測(PISCES, Mahalo-Suabru)を系統的に行った結果、環境にも依存した大局的(マクロ)な銀河 の形成進化の描像はかなり明らかになってきた。そして次は補償光学やアルマを使い、 高解像度で遠方銀河の内部構造を解剖するミクロなアプローチによって、形成・進化を 司る物理過程を突き止めることを目指している。本講演ではこれまでの研究 のハイライトと今後の展望についてレビューする。 第552回 題目Title:Technical Challenges in Scaling up to an Extremely Large Telescope 講師Speaker:Dr. Matt Johns (Telescope Scientist, The University of Arizona) 日時:5月9日(火)午後1時30分 〜 2時30分 Date: 9th May (Tues), 13:30 - 14:30 概要Abstract: The coming generation of Extremely Large Telescopes (ELTs) will be a factor 2.5 to 4 larger in diameter than the current generation of 6-10 meter ground-based optical/infrared telescopes. Their design and construction poses a set of technical challenges in scaling up from their smaller predecessors. This talk discusses a few of those challenges from the speaker's experience with one such project, the Giant Magellan Telescope (GMT). Many of the remarks apply to other ELT projects as well.
2016(H28)年度談話会 abstract 2015(H27)年度談話会 abstract 2014(H26)年度談話会 abstract 2013(H25)年度談話会 abstract 2012(H24)年度談話会 abstract 2011(H23)年度談話会 abstract 2010(H22)年度談話会 abstract 2009(H21)年度談話会 abstract 2008(H20)年度談話会 abstract 2007(H19)年度談話会 abstract 2006(H18)年度談話会 2005(H17)年度談話会 2004(H16)年度談話会