Colloquium 2008.4-2009.3, Dept Astronomy, Kyoto Univ

第431回
題 目：GLAST, HESS and Beyond, Status and Future of Gamma-ray Astronomy
講 師：Stefan Funk 氏　(Stanford University)
日 時：3月6日(金) 午後4時 〜 
(Mar 6 (Fri), 2009, 　16:00 -  )
概 要:
The field of gamma-ray astronomy has received considerable attention
beyond the high-energy astrophysics community in the recent
years. This is in part due to the success of Imaging Atmospheric
Cherenkov Telescopes (IACTs) such as Cangaroo-III, HESS, MAGIC and VERITAS,
measuring gamma-rays in the energy regime above 100 GeV. All these new
facilities have lifted gamma-ray astronomy in the last few years from
an exotic discipline with a handful of detected sources to a solid
astronomical discipline. In addition, the recent launch of the Fermi
Space Telescope (FST) and its main instrument, the Large Area
Telescope (LAT) measuring gamma-rays outside Earth's atmosphere in the
energy range beyond 100~MeV adds to the attention and excitement. The
Fermi-LAT instrument will solidify this discipline by detecting
several thousands of new sources and by bridging the energy spectra of
ground-based detected VHE gamma-ray sources to well-studies objects at
X-ray energies. In this seminar I will discuss the current status of
the field, as well as the potential for future observatories.。


第430回
題 目：Synthetic Delay Times of SNe Ia
講 師：Ashley J. Ruiter 氏
 (Harvard-Smithsonian Center for Astrophysics)
日 時：2月20日(金) 午後4時 〜 
(Feb 20 (Fri), 2009, 　16:00 -  )
概 要:
Type Ia supernovae are the most important distance indicators used in astrophysics, and 
play an important role in constraining cosmological quantities.  However, despite their use 
as standard candle distance indicators, their origin remains uncertain.  I will discuss the 
preliminary results from an ongoing study in which we have calculated delay time 
distributions of various SN Ia progenitors.  I will compare the delay time distributions 
resulting from three formation channels (SDS, DDS & AM CVn) for varying model assumptions 
(e.g., common envelope efficiency).  By comparing synthetic delay times with those which 
have been derived from observations, we aim to constrain the nature of the progenitor(s). 


第429回
題 目：天体衝撃波での高エネルギー粒子加速
講 師：星野　真弘  氏  (東京大学)
(Masahiro Hoshino)
日 時：2月10日(火) 午後4時 〜 
(Feb 10 (Tue), 2009, 　16:00 -  )
概 要:
宇宙空間には粒子の静止エネルギーを遥かに超える高エネルギーの荷電粒子が普遍的に存在する。こ
の高エネルギー粒子（宇宙線）は、超新星爆発や活動銀河核ジェットなどの超音速流にともなう衝撃
波によって作られていると考えられており、フェルミ加速と呼ばれる粒子加速機構が標準的な考え方
として受け入れられてきている。しかし現在においても、この加速機構には多くの未解決の問題があ
る。談話会では、近年のプラズマ粒子シミュレーションによって理解が進んできた、衝撃波での粒子
加速について議論する。


第428回
題 目：When and Where Did Early-Type Galaxies Form?
講 師：児玉　忠恭  氏  (国立天文台)
(Tadayuki Kodama)
日 時：1月7日(水) 午後4時 〜 
(Jan 7 (Wed), 2009, 　16:00 -  )
概 要:
Based on our two cluster surveys on Subaru, namely PISCES for 0.4＜z＜1.4 and HzRG for 2＜z＜5, 
we will show that the massive end of the red-sequence is being built up at z~2 in proto-
clusters, and the faint end of the red-sequence is being built up at z＜1.4 at the cluster 
outskirts.


第427回
題 目：Molecular outflows from young stars and protostars
講 師：Rafael Bachiller  氏
(National Astronomical Observatory, Spain)
日 時：12月2日(火) 午後4時 〜 
(Dec 2 (Tue), 2008, 　16:00 -  )

概 要:
The wealth of mm-wave observations being provided by large radiotelescopes
and interferometers on bipolar molecular outflows are reviewed. The physical outflow 
parameters are mainly obtained from CO observations, but we also pay attention to more rare 
and complex molecules such as CH3OH, H2CO, SiO, HCO+, etc. Recent results from chemical 
surveys of young protostellar outflows show that the peculiarities of the chemical behavior 
together with other structural parameters (such as the presence of molecular bullets, the 
flow opening angle, and the mechanical power efficiency) can be used to produce a 
classification of the observed outflows, and we suggest that this represents a rough time 
evolutionary sequence. We finally discuss the properties of the underlying primary wind which 
is assumed to drive the molecular outflows. Recent observations and theoretical work suggest 
that a primary wind with two components (a highly collimated jet and a wide-angle wind)is 
needed to explain the observations.


第426回
題 目：The Gemini Observatory, Current Status, The Future and Synergies
講 師：Chris Packham  氏
(University of Florida)
日 時：11月28日(金) 午後4時 〜 
(Nov 28 (Fri), 2008, 　16:00 -  )

概 要:
It is almost a decade since the current set of 8m-class telescopes saw first light, 
and the observatories are now achieving a level of maturity in their instrument 
suites and scientific output.   The Gemini Observatory and Subaru Telescope have 
several ongoing research activities across the facilities, including an exchange of 
observing time on our three 8-m telescopes, leading to an increasing level of 
synergy.  In May 2009 a joint Subaru-Gemini conference will be held in Kyoto with the 
goals to better understand the science and instrument paths of the observatories, 
and to explore areas of collaborations.  I present the current and future 
instrument suite of Gemini and science highlights, and encourage discussion of 
the possible future collaborations between the observatories.


第425回
題 目：GRAVITATIONAL MICROLENSING AND EXOPLANET SEARCHES
講 師：John W. Menzies 氏
(South African Astronomical Observatory)
日 時：11月10日(月) 午後4時45分 〜 
(Nov 10 (Mon), 2008, 　16:45 -  )

概 要:
   Gravitational microlensing has come of age as a powerful tool
   in the search for extrasolar planets with the discovery
   in the last few years of eight new   planets, including
   what was at the time the lowest mass exoplanet known.
   The PLANET collaboration, with its worldwide network of
   telescopes, including the SAAO 1.0-m at Sutherland, was
   a pioneer in using this search technique. This talk will
   discuss PLANET's contribution to microlensing research
   and the prospects for the future.


第424回
題 目：The Current Status of the Extragalactic Distance Scale
講 師：Michael W. Feast 氏
(Department of Astronomy, University of Cape Town)
日 時：11月10日(月) 午後4時 〜 
(Nov 10 (Mon), 2008, 　16:00 -  )

概 要:
This will be a general review of distance indicators and their
   Galactic and Extragalactic use, including the determination of
   the Hubble constant (Ho) and the distance to the Galactic
   Centre (Ro). Present uncertainties and current projects to
   reduce them will be discussed.


第423回
題 目：The optical depth of the Universe 
　　　　seen through ultrahigh energy cosmic ray spectacles
講 師：Dr. Kumiko Kotera  (Institute of Astrophysics of Paris, France)
日 時：9月30日(火) 午後5時30分 〜 
(Sep 30 (Tue), 2008, 　17:30 -  )

概 要:
The origin of ultrahigh energy cosmic rays has not yet been unveiled, in spite of decades of
theoretical and experimental investigations. It is mostly challenging to hunt the sources of these
charged particles, as they propagate in a magnetized medium. We provide an analytical description of
the transport of ultrahigh energy cosmic rays in a universe made up of magnetized scattering centers
such as radio cocoons, magnetized galactic winds, clusters or filaments of large scale structure,
with negligible magnetic fields between them.
We present the notion of optical depth of the Universe to cosmic ray scattering and discuss its
phenomenological consequences for various source scenarios. It is found that part of the correlation
reported recently by the Pierre Auger Observatory between active galactic nuclei and the arrival
directions of ultrahigh energy cosmic rays may be affected by a scattering delusion. This experiment
may be observing in part the last scattering surface of particles, rather than their source population.


第422回
題 目：X線ガンマ線観測による銀河系内天体の研究
講 師：内山　泰伸 氏
(宇宙航空研究開発機構・宇宙科学研究本部)
日 時：8月1日(金) 午後4時 〜 
(Aug 1 (Fri), 2008, 　16:00 -  )

概 要:
 本談話会では、われわれ「すざく」衛星の観測チームが、大気チェレンコフ望遠鏡HESSのグループと
共同で行っている銀河系内天体の研究について紹介する。共同研究の対象は、超新星残骸、パルサー
風星雲、ガンマ線連星、未同定TeVガンマ線源など多岐にわたるが、今回は超新星残骸とガンマ線連星
について報告する。前者については、最もTeVガンマ線の強い2つの超新星残骸RX J1713.7-3946 と 
Vela Jr をとりあげ、宇宙線陽子が超新星残骸の衝撃波において加速されていることの観測的証拠を
示す。後者については、ガンマ線連星PSR B1259−63 の大規模な観測キャンペーンの結果を紹介す
る。PSR B1259−63 はパルサー風と星風(星
周円盤)の相互作用が見られるユニークな連星であり、時々刻々と変化する環境においてパルサー風衝
撃波における粒子加速を探求できる唯一の天体である。今回は特に「すざく」衛星によってはじめて
明らかになったスペクトル構造を示してX線放射機構を議論する。


第421回
題 目：再帰新星 RS Ophの分光観測：2006年のアウトバーストで解明されたことと新たな謎
講 師：飯島　孝 氏
(イタリア国立パドバ天文台、アジアゴ観測所)
日 時：8月1日(金) 午後2時 〜 
(Aug 1 (Fri), 2008, 　14:00 -  )

概 要:
 再帰新星 RS Ophが2006年に21年ぶりのアウトバーストを起こしたので、そのスペクトルの
変化について詳細な観測を行った。RS Ophの周囲には静穏時における赤色巨星からの定常的
なガスの放出によって形成された星周雲が存在するので、アウトバーストで放出された高速
ガスがその星周雲と衝突することによりコロナ輝線やＸ線輻射が発生する。それが古典新星
との大きな違いである。コロナ輝線はアウトバーストの開始からほぼ100日で消失し、それと
同時に[O I], [N II], [O III] 等の輝線が急速に強くなった。その時点で高速ガスが星周
雲を吹き払って、自由膨張が始まり、電子密度が低下したと考えられる。その結果から星周
雲の大きさや質量を推定した。その一方で光球の振動に起因すると思われる、He I輝線の強
度の突発的な変化が観測された。これはRS Oph ではこれまで知られていなかった現象である。

また、多くの輝線は高速ガスに起因する巾の広い成分と、星周雲に起因する巾の狭い成分
によって構成されているが、コロナ輝線と水素、ヘリウムの輝線に限り、その巾の狭い輝線
成分が二つに分裂するという現象が発見された。分裂の巾は 50 km/s 程度なので、高速ガス
に関係しているとは考えにくい。しかし星周雲に起因すると考えられる [N II], [O III],
[Fe VII], Fe II 等の輝線ではそのような分裂はまったく見られなかった。この現象は今
のところ解釈不能、「いはく不可解」である。


第420回
題 目：Probing the dusty disks of high-mass protostellar objects
講 師：Dr. Zhibo Jiang 
　　　　(Purple Mountain Observatory, Nanjing, China)
日 時：7月25日(木) 午後4時 〜 
(July 25 (Fri), 2008, 　16:00 -  )

概 要:
The presence of accretion disks around high-mass protostars has been 
long speculated until recently, a number of disks of various type have 
been discovered.  Given the scattering properties of dust grains, it is 
rather easy to detect the dusty disk around the high-mass protostars. We 
present near-infrared polarimetric images of several high-mass 
protostellar objects. These images show the bipolar morphology, 
suggesting the anisotropic distribution of dust around the objects. 
Further analysis suggests that such a kind of morphology can be best 
interpreted as a dusty disk around these objects. Monte Carlo 
simulations by assuming different dust properties and disk inclination 
angle confirm the interpretation.  In view of the advantage of 
high-resolution near-infrared polarimetric images, we propose that such 
a method is one of the best approaches to probe the dusty disks around 
high-mass protostars.

Keywords: near infrared; polarization; star formation; high-mass stars; 
circumstellar disk


第419回
題 目：数値相対論と重力波
講 師：柴田　大　氏
（東京大学大学院総合文化研究科）
日 時：7月17日(木) 午後4時 〜 
(July 17 (Thu), 2008, 　16:00 -  )

概 要:
　アインシュタイン方程式と相対論的運動方程式を同時に解いて、連星中性子星や
連星ブラックホールの合体、大質量星の重力崩壊といった相対論的天体現象を理論
的に研究する分野を数値相対論と呼ぶ。数値相対論はここ数年の間に、急速に発展
したが、その現状を述べると共に、現在どの程度詳しく重力波源からの重力波の予
想が可能なのかについて解説する。 


第418回予定
題 目：Photo-Dynamic Models of Isolated and Merging Galaxies
講 師：Professor Joshua Edward BARNES
（Kyoto University & University of Hawaii）
日 時：7月14日(月) 午後2時 〜 
(July 14 (Mon), 2008, 　14:00 -  )

概 要:
A number of groups have implemented gas dynamics and star formation in
numerical models of interacting galaxies.  With these models as a starting
point, one can go on and include photometric evolution and radiative
transfer in a dusty ISM; the results may be compared in detail to
observational data on isolated and interacting galaxies.  A sequence of
isolated models matching the photometric properties of ordinary disk
galaxies is generated; this sequence reproduces the Tully-Fisher relation.
Collisions of these models are then used in an attempt to recreate the
interacting galaxies NGC 4676 and the merger remnant NGC 7252.


第417回
題 目：The COSMOS AGN Survey: 
　　　　Understanding the Nature of AGN Fueling and Obscuration
講 師：Dr. Jonathan Trump  (Univ. of Arizona / Ehime Univ.)
日 時：7月11日(金) 午後2時 〜 
(July 11 (Fri), 2008, 　14:00 -  )

概 要:
The Cosmic Evolution Survey (COSMOS) provides a unique opportunity for the
study of AGN.  With a combination of deep radio (VLA), infrared (Spitzer
MIPS & IRAC), optical (Hubble/ACS & 21-band Subaru/Suprime-Cam), UV
(GALEX), and X-ray (XMM & Chandra) observations, COSMOS makes possible the
first true "bolometric" study of AGN.  I will present results from a
3-year spectroscopic survey of X-ray and IR selected AGN in COSMOS using
the Magellan/IMACS and MMT/Hectospec instruments.  This spectroscopic
sample reaches the customary quasar/Seyfert luminosity boundary at z~2,
and also reveals Type 1 AGN with black hole masses of only 10^7 M_sun to
z~2.  The IR selection additionally allows us to observe a large number of
heavily obscured AGN, which recent pencil-beam surveys have revealed to be
a significant fraction of the total AGN population.  Using COSMOS, we can
suggest new limits on accretion rate for Type 1 AGN, probing the accretion
physics of a stable BLR.  COSMOS also reveals significant luminosity
dependence and redshift evolution in the obscured fraction of AGN, and I
will discuss a few of the physical models for obscuration which are
suggested by the observations.


第416回
題 目：TeV emission from binaries
講 師：Dr. Andrzej A. Zdziarski
（コペルニクス天文学センター）
日 時：6月17日(火) 午後2時 〜 
(Jun 17 (Tue), 2008, 　14:00 -  )

概 要:
 I will discuss models of the TeV emission from X-ray binaries, discovered
 in recent years by the HESS and MAGIC telescopes. In the case of PSR
 B1259-63, LS I 61+303 and LS 5039, the most likely model of the observed
 persistent emission is interaction of the electron-positron pair wind
 emitted by a young pulsar with the stellar wind from the high-mass Be/O
 companion. Cyg X-1 is now the only case of TeV emission from a confirmed
 accreting binary. It is found that the observed transient emission can
 originate from the central X-ray source in spite of photon-photon pair
 absorption due to the Klein-Nishina decline of the pair-production cross
 section. 


第415回
題 目：What star clusters can tell us about dark matter and gravitation
講 師：Dr. Holger Baumgardt　（ボン大学）　
日 時：5月8日(木) 午後1時半 〜 
(May 8 (Thu), 2008, 　13:30 - )

概 要:
 The dark matter paradigm and cold dark matter (CDM) cosmology are widely
 accepted theories on which much of our understanding of the properties and
 evolution of the Universe is based. Yet these paradigms face a number of
 serious problems. A heuristic alternative to dark matter is the theory of
 modified Newtonian dynamics (MOND) and its relativistic formulation TeVeS.
 For more than 20 years, MOND has successfully defied all attempts to
 disprove it. In a previous paper (Baumgardt, Grebel, & Kroupa 2005), we
 have shown that it is possible to test MOND and the dark matter paradigm
 by measuring internal velocity dispersions of star clusters in the outer
 halo of the Milky Way. In my talk I will report first results from these
 studies. I will also discuss other evidence for dark matter in globular
 clusters.


第414回
題 目：Recent developments in extrasolar planetary science
講 師：Dr. Michael Richmond (Rochester Institute of Technology)
日 時：4月24日(木) 午後2時 〜 3時
(April 24 (Thu), 2008, 　14:00 - 15:00)

概 要:
The first planets circling another star were detected
in 1995.  Since then, the number of extrasolar
planets have grown: we now know of 228.  In the
past few years, astronomers have used new techniques
to find planets.  We have just begun to measure properties
of the atmospheres in a few systems.   I will 
provide an overview of recent progress in extrasolar
planetary science, concentrating on the newest results.
I will also describe the fleet of satellites which are
now observing extrasolar planets, and those which will
soon be launched.


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