FrontPage

第177回: 2011/05/19(木) 15:30-16:30

田村 陽一 氏 (東京大学・天文学教育研究センター)

「ASTE搭載用超伝導転移端センサ型ボロメータカメラとALMA初期科学運用」
"The new TES bolometer camera for ASTE and the ALMA early science operation"

 東京大学天文センター・国立天文台・北海道大学は、チリ・アタカマ砂漠に設置された
ASTE望遠鏡への搭載を目的とした超伝導転移端センサ型ボロメータカメラ開発を、
2009年より推進している。本カメラは本年7月にASTE望遠鏡に搭載され、1100、850ミクロン
(将来的には450ミクロンも)における地上天文観測を開始する予定だ。
その観測対象は、遠方銀河・銀河団、ガンマ線バースト、マゼラン雲、原始惑星系円盤と
多岐にわたる。本講演の前半では、ASTE観測所の現状、本サブミリ波カメラプロジェクトの
サイエンスケース、および進捗を紹介する。
 本講演の後半では、いよいよ開始されるALMAの初期科学運用に触れたい。
3月末に観測提案公募の情報が、のべ100ページに迫る複数の文書とともに公表された。
この公募の独特な点は、世界各国の電波天文学者の注目の高さもさることながら、
観測提案者・提案内容に課せられた条件の多さにあると言える。ひとりのユーザの視点から、
初期運用フェイズのALMAの性能・観測公募の内容を読み解きたい。

第178回: 2011/06/16(木) 15:30-16:30

Michael Richmond 氏 (Rochester Institute of Technology)

"Looking for eclipsing RR Lyr stars in the MACHO database"

The MACHO Project collected photometry of many RR Lyrae stars from its observations of the Milky Way's bulge.
We examined the lightcurves of 3256 stars identified as RRab Lyr variables by Kund et al. 2008,
subtracting an empirical model of the pulsation lightcurve and searching for periodic variation in the residuals.
There are no systems which show the brief dips in light characteristic of detached eclipsing binary systems.
We discuss the results for objects which show the largest residual periodic modulation,
most of which are probably due to aliases of the fundamental period.
(See http://arxiv.org/abs/1106.0697.)

第179回: 2011/06/30(木) 15:30-16:30

田中 賢幸 氏 (東京大学・IPMU)

"A new method to identify AGNs and the nature of low-luminosity AGNs"
 
We develop a new method to identify AGNs using optical spectra of galaxies. 
The newly developed method is fairly sensitive to low-luminosity AGNs and 
also it allows us to cleanly subtract emission line fluxes due to star formation 
and extract pure AGN emission, which is crucial to characterize AGN activities. 
We study the nature of the identified low-luminosity AGNs with black hole masses, 
accretion rates and host galaxy properties.  
Our findings include 
(1) AGNs reside in massive galaxies (>1010 M_sun),
(2) accretion rates increase with increasing host galaxy star formation rates, and 
(3) black hole growth rates increase with increasing host galaxy growth rates. 
We discuss implications of these findings for the BH-galaxy co-evolution.

第180回: 2011/07/07(木) 15:30-16:30

橋本 哲也 氏 (国立天文台)

"A hint of AGN feedback: Shock heating of ISM induced by a jet in NGC 1068"
 
We present J-band long-slit spectroscopic observation of
NGC 1068 classified as a Seyfert 2 galaxy. J-band observations
with OAO/ISLE provide clear detection of spatially extended [Fe II]1.257um
and [P II]1.188um lines. We found that [Fe II]1.257um/[P II]1.188um
increases with distance from a central continuum peak. Observed line
ratios around the nucleus (continuum peak) are consistent with a typical
value expected from photoionization models, while the ratios at
3 arcsec - 4 arcsec (210-280 pc) east and west of the nucleus
are slightly higher than this. In the off nucleus region of NGC 1068
we also found a possible association between [Fe II]1.257um/[P II]1.188um
and the radio continuum. This suggests a mild contribution of shock
ionization induced by a radio jet outside nucleus while photoionization by
the central energy source is dominant near the nucleus. This result is
a hint to investigate the on going site where the AGN activity inputs
its energy to surrounding interstellar medium (ISM) through a shock heating
induced by a jet. This kind of energy input into ISM may be the
key to reveal a recently emerged serious problem that theoretical simulations
predict too many massive galaxies due to long-duration star formations in
contrast to early-time quenching of star formation in observed massive galaxies,
and may be also closely correlated with the co-evolution of super massive black
hole and its host galaxy. We also present preliminary result of J-band integral
field unit spectroscopy (NIFS+AO) of narrow line region in NGC 1275.

第181回: 2011/07/21(木) 15:30-16:30

柏川 伸成 氏 (国立天文台)

「AKB48 vs. NMB48 vs. SKE48, そして LAE45vs.LAE54」
"Completing the Census of Lyα Emitters at the Reionization Epoch"

We carried out extended spectroscopic confirmations of Lyα emitters (LAEs) at z = 6.5 and 5.7 
in the Subaru Deep Field. Now, the total number of spectroscopically confirmed LAEs is 45 and 54 
at z = 6.5 and 5.7, respectively, and at least 81% (70%) of our photometric candidates 
at z = 6.5 (5.7) have been spectroscopically identified as real LAEs. 
We made careful measurements of the Lyα luminosity, both photometrically and spectroscopically, 
to accurately determine the Lyα and rest-UV luminosity functions (LFs). 
The substantially improved evaluation of the Lyα LF at z = 6.5 shows an apparent deficit 
from z = 5.7 at least at the bright end, and a possible decline even at the faint end, 
though small uncertainties remain. The rest-UV LFs at z = 6.5 and 5.7 are in good agreement, 
at least at the bright end, in clear contrast to the differences seen in the Lyα LF. 
These results imply an increase in the neutral fraction of the intergalactic medium 
from z = 5.7 to 6.5. The rest-frame equivalent width (EW_0 ) distribution at z = 6.5 
seems to be systematically smaller than z = 5.7, and it shows an extended tail toward larger EW_0 . 
The bright end of the rest-UV LF can be reproduced from the observed Lyα LF and a reasonable 
EW_0 -UV luminosity relation. Integrating this rest-UV LF provides the first measurement of 
the contribution of LAEs to the photon budget required for reionization. The derived UV LF 
suggests that the fractional contribution of LAEs to the photon budget among Lyman break galaxies 
significantly increases toward faint magnitudes. Low-luminosity LAEs could dominate 
the ionizing photon budget, though this inference depends strongly on the uncertain 
faint-end slope of the Lyα LF.

第182回: 2011/07/28(木) 15:30-16:30

上塚 貴史 氏 (東大・天文センター)

"Mid-infrared spectral monitoring toward AGB stars - Probing the formation of circumstellar dust - "

Asymptotic giant branch (AGB) stars are the stars in the final evolutionary stage of low- 
and intermediate-mass stars. They are known to show mass-loss events caused by their stellar wind, 
and the events play an important role for chemical evolution of the universe. 
The stellar wind is thought to be driven by radiative pressure on dust formed around the central star. 
After the grains are formed, they are accelerated by the radiation from inner region, 
and the gaseous material is accelerated by the gas-dust collisions. 
This scenario has not been fully investigated by observations. It is important to probe 
when, where and what kind of grains are formed around the region where the stellar wind is driven, 
and mid-infrared spectral monitoring is one of useful methods. 
As an example, I will present our monitoring observation toward HV2446 and IRAS04544-6849, 
which are Mira type variables in the Large Magellanic Cloud, taken with Spitzer Space Telescope. 
Both objects showed time variation of silicate features. These variations can be explained 
mainly by the temperature variation caused by the luminosity variation of the central star. 
However, the strength and the shape of the feature around the visual maximum phase cannot be 
explained by this effect. This suggests possibility of the dust formation around this phase. 
From this result, the monitoring observations are thought to have big potential to probe the grain formation events. 
In this talk, I will discuss about this result and the usefulness of long-term monitoring observations with mini-TAO and TAO.

第183回: 2011/10/06(木) 15:30-16:30

眞山 聡 氏 (総研大)

「すばる+ALMA及びコンピュータシミュレーションで探る連星系原始惑星系円盤」
"Subaru + ALMA Observations and numerical simulations of Protoplanetary Disks in a Young Multiple star"

Protoplanetary disks afford a key to an understanding of the formation of our Solar System 
and other planetary systems.  They are the ingredients of planets and play important roles 
in early stellar evolution.  If a forming star with a protoplanetary disk has close companions, 
the disk may be seriously influenced.  This effect should not be ovelooked 
because most stars form as multiples.  Studies of protoplanetary disks in multiple systems are 
thus important to unravel the general process of star and planet formation. 
From this point of view, we conducted Subaru direct observations of protoplanetary disks 
in multiple systems.  High angular resolution near-infrared adaptive optics images of 
young binaries were obtained with the infrared camera Coronagraphic Imager 
with Adaptive Optics mounted on the 8.2m Subaru Telescope. Our 0."1 resolution images 
resolve complex circumstellar structures around binary systems.  We present our observational 
result as well as 2D and 3D numerical simulations which reproduce accretion onto the binary system. 
Additionally, our observational future plans of multiple protoplanetary disks using ALMA will be introduced.

第184回: 2011/10/13(木) 15:30-16:30

Gaston Folatelli 氏 (東京大学・IPMU)

"What spectra reveal of Type Ia Supernovae"

I will address the importance of Type Ia supernovae (SNe Ia) as astrophysical objects, 
and also as distance indicators for cosmology. Based on data from the Carnegie Supernova 
Project (CSP), I will describe how precision distances are obtained, with a detailed characterization 
of reddening. The role of optical spectroscopy in improving our understanding of the physical 
nature of these events will be addressed. In particular, I will show a recent finding of unburned 
material in a significant fraction of SNe Ia, and its implications on explosion physics.

第185回: 2011/10/17(月) 15:30-16:30

Wolfgang Gieren 氏 (Universidad de Concepcion)

"Improving the extragalactic distance scale with stellar distance indicators: The Araucaria Project"

I will review recent progress made in our project towards calibrating the classical Cepheid 
period-luminosity (PL) relation, both from observing Cepheid samples in nearby galaxies 
in optical and near-infrared bands, and by applying the Infrared Surface Brightness Technique 
to Cepheids in the Milky Way and the Magellanic Clouds. 
Evidence is presented that the K-band PL relation is universal (e.g. independent of the metallicity 
of the calibrating or target Cepheid samples), and a best absolute PL relation is presented 
which can be readily used to measure a precision distance to any galaxy containg classical Cepheids.

I will also review recent progress in using late-type eclipsing binary systems in the Magellanic Clouds 
for deriving distances of exquisite (3%) accuracy to the Clouds, setting a very accurate zero point 
for the distance scale. I will further present our recent determination of the first accurate dynamical 
masses of two classical Cepheids in the LMC which settle the Cepheid mass discrepancy problem 
and improve the physical knowledge of Cepheid stars as primary distance indicators.

Finally, I will highlight a new spectroscopic method to measure accurate distances
to spiral galaxies from their blue supergiant population, and demonstrate that this new 
technique yields distance results in very good agreement with Cepheids. 
Quantitative spectroscopy of blue supergiants is also an excellent means to establish correct, 
unbiased metallicity gradients in the disks of spiral galaxies 
which are an essential input for galaxy formation and evolution scenarios.

第186回: 2011/11/24(木) 15:30-16:30

高橋 英則 氏 (東京大学・天文センター)

「近赤外分光撮像観測によるWolf-Rayet星の探索」
"Search for Wolf-Rayet stars by NIR imaging spectroscopy"

Wolf-Rayet星は大質量星故のエネルギー放射や質量放出によって、周辺の星間物質の形成や変成、
さらに次世代の星形成などに大きな影響を与える。ところで、これまでに見つかっているWR星は
銀河系の化学進化から想定される数よりも少ない。その原因の一つとして、WR星の寿命の短さや
形成される環境の観点から、その一生を星間物質に埋もれたまま過ごしている可能性が考えられる。
そこで、その素性及びどのような環境で誕生・進化するかを明らかにすることを目的として、
このような埋もれたWR星を検出すべく、近赤外分光撮像による探索を行っている。
この手法として、WR星に特徴的な近赤外線(WC型:CIV輝線(2.076um)、WN型:HeII(2.189um))
に最適化された狭帯域フィルターとKsバンドフィルターを用いる。狭帯域撮像の画像ベースで
処理することで、効率的且つ高い確度でWR星を検出することができる。これまでこの手法を用い、
減光が大きな銀河中心方向や系内大質量星形成領域、LMCなどでWR星の探索を進めてきた。
これらの領域は、1) 星形成活動度が高い、2) 広い質量範囲の星が存在する、3) ダスト形成が
盛んな環境である、などの理由から、大質量星形成に限らず、星間物質やIMFの研究に非常に
興味深い領域である。講演では、この観測手法の詳細から現在までの観測の進捗、今後の展開について述べる。

第187回: 2011/12/01(木) 15:30-16:30

松永 典之 氏 (東京大学・天文センター・木曽観測所)

「セファイド変光星で探る銀河系中心領域の星形成史」
"Star formation history in the Galactic Nuclear Bulge revealed with Cepheid variable stars"

銀河系中心は、非常に多くの星・星間物質やブラックホール、強い磁場などが混在する複雑で
興味深い領域である。銀河系中心から200pc程度の領域(Nuclear Bulge)では数Myrの年齢を
もつ大きな星団が見つかっており、今も星形成が起 こっていると考えられている。
また、現在までの星形成が連続的であったことも 示唆されているが(Figer et al. 2004, ApJ, 601, 319)、
その結論は光度関数と の比較によるもので、間接的・暫定的である。
そこで、恒星進化理論から年齢の わかるセファイド変光星の探査を行った。
IRSF望遠鏡およびSIRIUSカメラを用い て、2001年から2008年の間にを行った近赤外線反復観測の結果、
セファイド変光 星を3個発見することに成功した。それらの周期はいずれも20日程度で、
約25Myr の年齢を持つことが分かる。今から25Myr前にNuclear Bulgeで星形成が起こって いたことを
示す初めての証拠である。一方、周期5-19日(30-70Myrの年齢に対応) のセファイド変光星は
見つからなかった。 このことは、数十MyrごとにNuclear Bulge中での星形成率が変化することを
示唆しており、銀河系中心領域での星間 物質の供給・消費などについて重要なヒントを与えるものと期待される。
参考文献:Matsunaga et al. 2011, Nature 477, 188

The region within ~200 pc of the central black hole of our Galaxy, often called the Nuclear Bulge, 
is an ideal place to study star formation activities in galaxy centres in detail. Stellar populations 
with a wide range of ages are found in this region, but the star formation history remains uncertain. 
Here we report the first discovery in the Nuclear Bulge of classical Cepheids, pulsating supergiants, 
whose ages can be derived accurately from their periods. All three of our Cepheids have pulsation 
periods near 20 days and an age of close to 25 Myr. In contrast, the absence of shorter-period 
Cepheids shows that the star formation rate was much lower between 30 and 70 Myr ago. 
This indicates that star formation in the Nuclear Bulge varies on a time scale of a few tens of Myr. 
Such detailed star formation histories have never been obtained for central parts of this or 
other galaxies. We discuss a correlation between the gas inflow and star formation around the Galactic Centre.

第188回: 2011/12/08(木) 15:30-16:30

野田 博文 氏 (東京大学)

「X線観測で明らかにする AGN セントラルエンジンの新描像」
"Studying a new picture of AGN Central Engines with X-ray Observations"

AGNのX線放射は、降着円盤や冷たい周辺物質による光子散乱散乱過程、ジェット中の高エネルギー過程
などの観点から、盛んに研究されてきた。しかしセイファート銀河などにおける一次放射の源、
すなわち巨大ブラックホール近傍の高温コンプトンコロナそのものに迫る研究は、これまで驚くほど乏しかった。
AGNを理解する上で、このセントラルエンジンの理解は、避けて通れない重要課題である。

我々は、広帯域を誇る「すざく」衛星を用い、AGNのX線放射に現れる「相対論的に広がった鉄輝線」や
軟X線超過の起源を見直すとともに、「すざく」によるブラックホール連星 Cyg X-1 の研究とも緊密に連携してきた。
その結果、これまで単一ゾーンで近似されて来たセイファート中心核の高温コロナが、実は様々な電子温度や
光学的厚みから成るマルチゾーン特性をもつという、新しい可能性を見いだした (Noda et al. 2011a, b)。
本談話会では、この着想に至った我々の研究を紹介すると同時に、同様の描像を他種のAGNで検証した結果や、
開発中の次期X線天文衛星ASTRO-Hを視野に入れた将来の研究についても触れたい。

第189回: 2011/12/15(木) 15:30-16:30

松元 亮治 氏 (千葉大学)

「円盤ダイナモとブラックホール候補天体における状態遷移の磁気流体数値実験」
"Magnetohydrodynamic Simulations of Disk Dynamos and State Transitions in Black Hole Candidates"

Three-dimensional magnetohydrodynamic(MHD) simulations revealed that quasi-periodic dynamos 
driven by the magneto-rotational instability and Parker instability are excited in accretion disks and 
in galactic gas disks. 
The quasi-periodic dynamo can be the origin of low-frequency (1-10Hz) quasi-periodic oscillations 
 (QPOs) observed in galactic black hole candidates. 
By carrying out global three-dimensional MHD simulations of black hole accretion disks, we found 
that the transition luminosity from X-ray hard state to X-ray soft state depends on the azimuthal 
magnetic flux in the accretion disk. We discuss how the evolutionary track in the color-luminosity 
plane is determined in black hole accretion flows.

降着円盤や銀河ガス円盤などの差動回転円盤では磁気回転不安定性とパーカー不安定性の相乗効果によって
駆動される準周期的なダイナモが発生することが、3次元磁気流体シミュレーションによって明らかになった。
このような準周期的ダイナモは銀河系内のブラックホール候補天体で観測されている1-10Hzの準周期振動
(Quasi-Periodic Oscillation:QPO)の起源になっている可能性がある。
輻射冷却を考慮した大局的な3次元磁気流体シミュレーションの結果、ブラックホール候補天体で観測される
色-光度図上の進化経路、特に硬X線が強いハードステートから軟X線が強いソフトステートへの
状態遷移光度は円盤内部の方位角方向の磁束量に依存することが示唆された。
降着率変動に伴う降着円盤の進化を、3次元磁気流体計算結果に基づいて議論する。

第190回: 2012/01/26(木) 15:30-16:30

Parthasarathy Mudumba (Indian Institute of Astrophysics, Bangalore, India)

"Progenitors of Type Ia SNe : Binary stars with white dwarf companions"

Type Ia SNe are thought to come from carbon-oxygen white dwarfs that accrete mass from 
binary companions until they approach the Chandrasekhar limit, ignite carbon, and undergo
complete thermonuclear disruption. A survey of the observed types of binaries that contain
white dwarfs is presented. All types of white dwarf + main-sequence binaries , white dwarf + red giant
binaries,  close-binary central stars of planetary nebulae, recurrent novae,  double-degenerate
binaries, supersoft X-ray sources and V Sge type objects  will be discussed. In view of the number
of promising single-degenetate systems and the dearth of promising double-degenerate systems,
it appears that single-degenerate binaries produce most or perhaps all SNe Ia, while 
double-degenerate binaries produce some or perhaps none.

第191回: 2012/02/02(木) 15:30-16:30

菅井 肇 (東京大学・IPMU)

"Two Instruments for Subaru Telescope"

すばる望遠鏡は、優れた結像性能と広い視野に大きな特徴を持つ。結像性能の良さに着目し
京都三次元分光器第2号機の開発を行ってきた。とくに高空間分解能の面分光観測により、
若い活動銀河中心核からのアウトフローの研究や、重力レンズ天体を利用した研究などを
行ってきた。さらなる発展として、すばる新補償光学システムAO188との接続試験を
4月に予定している。一方で、現在、広い視野を有効に活かすためのPrime Focus Spectrographの
開発を進めている。2400本のファイバを、3色腕を持つ4台の分光器に分割し、
1.3度視野直径にある天体を同時に分光(0.38-1.3um)観測するという挑戦的な装置で、
宇宙論・銀河系形成・銀河進化などの分野に威力を発揮すると考えられる。
3月に行われる概念設計審査に向けて準備を進めている。

第192回: 2012/03/08(木) 15:30-16:30

Kevin Bundy (University of Tokyo, IPMU)

"Building massive galaxies: Hierarchical assembly from panoramic surveys and the coming era of integral field spectroscopy"

The physical processes that regulate the growth of massive galaxies remain poorly understood. 
Globally, it is expected that such galaxies assemble at late times, but this basic prediction of 
hierarchical models is largely untested because cosmic variance in the small volumes sampled by 
current high-z surveys swamps any potential signal.  Thankfully, an array of next-generation 
panoramic surveys will bring definitive answers.  I will discuss early results from measurements of 
galaxy assembly with one such survey, the now 50% complete Baryon Oscillation Spectroscopic 
Survey (BOSS).  Turning from surveys limited to only the integrated properties of distant galaxies, 
I will then discuss new observational efforts in the coming era of IFU spectroscopic surveys.  
I will introduce a proposed extension of the SDSS called MaNGA that, if approved, would provide 
2D measures of kinematics, emission line diagnostics, and absorption line probes for 10,000 
nearby galaxies.  Surveys like MaNGA will test specific mechanisms that may be driving the growth 
and evolution revealed in wide-field redshift surveys.

第193回: 2012/03/15(木) 15:30-16:30

資料: filepptx, filepdf

Kenneth C. Chambers (Institute for Astronomy, University of Hawaii)

"Pan-STARRS1 - Status and Early Science"

Pan-STARRS1 began the PS1 Science Mission May 13, 2009. 
Operations of the PS1 System include the Observatory, Telescope, 
1.4 Gigapixel Camera, Image Processing Pipeline , PSPS relational 
database and reduced science product software servers.

The PS1 Surveys include: (1) A 3pi Steradian Survey; 
which current has obtained more than 30 epochs in 5 passbands (grizy)
of the entire sky north of Dec = -30, or 30,000 square degrees
with 0.26 arcsecond pixels, or nearly 2 Petabytes of images;
(2) A Medium Deep survey of 10 PS1 footprints spaced around
the sky or a total of 70 square degrees; (3) A solar system ecliptic
plane survey optimized for the discovery of Near Earth Objects and
Kuiper Belt Objects, (4) a Stellar Transit Survey of ~50 square degrees in
the galactic buldge; and (5) a Deep Survey of M31 with special attention
to a proper cadence for microlensing.

The performance of the PS1 system, sky coverage, cadence, and
data quality of the images, the photometric calibration, and astrometric
precision will be presented.  Early science ranging from the solar system,
brown dwarfs, galactic structure, supernovae, and galaxy counts will be
presented.  The completion of the PS1 Survey, the status of PS2 and
plans for a PS1+PS2 Mission will be briefly addressed.

The PS1 Science Consortium consists of The Institute for Astronomy
at the University of Hawai'i in Manoa, the Max Planck Institute for Astronomy,
Heidelberg, the Max Planck Institute for Extraterrestrial Physics, Garching,
The Johns Hopkins University, the University of Durham, the University of
Edinburgh, the Queen's University Belfast, the Harvard-Smithsonian Center
for Astrophysics, the Los Cumbres Observatory Global Telescope Network
Incorporated, the National Central University of Taiwan, and NASA through 
the NEOO program.

添付ファイル: filekcc_ps1_uni_tokyo.pptx 997件 [詳細] filekcc_ps1_uni_tokyo.pdf 1210件 [詳細]

トップ   編集 凍結 差分 バックアップ 添付 複製 名前変更 リロード   新規 一覧 検索 最終更新   ヘルプ   最終更新のRSS
Last-modified: 2012-03-16 (金) 09:22:58