総研大天文科学専攻ウェブログ

[Speaker 1]
Nobuharu Sako

[Title]
Time evolution of X-ray jet's velocity

[Abstract]
An X-ray jet is a kind of flares in the Sun. The model of X-ray jets based on magnetic reconnection (Shibata et al. 1992) predicts that two flows with the different velocities are included in one X-ray jet. The velocity of one flow roughly equals to Alfven velocity (~1000 km/s), and the flow is accelerated by the magnetic force. The other one is
accelerated by the pressure gradient and its velocity is similar to the sound velocity (~200 km/s). However, the observational results (e.g. Shimojo et al. 2000) before the Hinode era show that the velocities of most X-ray jets are slower than the sound velocity.
Because the X-ray telescope (XRT) aboard the Hinode satellite has capability to observe the corona with the high temporal (< 1 min) and high spatial (~ 1 arcsec) resolutions, the XRT data revealed that an X-ray jet includes two components with the different velocities
(Cirtain et al. 2007). The properties of the components have some differences from the model. For example, the components are not observed simultaneously. One component with sound velocity continues to appear until the peak time of the X-ray jet. The other one with Alfven velocity appear transiently.
There is only one report using four X-ray jets by Cirtain et al. (2007) and their result does not show the time evolution of the velocity in X-ray jets, yet. In order to reveal the evolution of the X-ray jet's velocity, and investigate how the high velocity component
occurs transiently in an X-ray jet, we detected 13 polar X-ray jets from the coronal data observed with XRT and investigated the time evolution of the velocity of the X-ray jets. The result shows that it is common that an X-ray jet includes the plural components with the different velocities. However, we could detect component with Alfven velocity in only three of the 13 events.
In the talk, I introduce our data analysis and show the details of our result.

[Speaker 1]
Jungmi Kwon

[Title]
NEAR INFARED CIRCULAR POLARIZATION IMAGES OF NGC 6334 V

[Abstract]
We present results from deep imaging polarimetry measurements of circularly and linearly polarized light towards the massive star forming region NGC 6334-V. These observations show high degrees of circular polarization (CP) in the Ks band of as much as 22 % with an asymmetric positive/negative pattern, measured in the infrared nebula associated with the outflow. The CP region is very extended (~80" or 0.65 pc). Both the large CP and the extended size of the CP region are comparable to those seen in the Orion CP region. The CP pattern is shifted along the axial axis and such an asymmetry does not conform to the classical alternating symmetry seen in other objects and models.
The asymmetry may be a clue indicating the range of influence of a helical field. Three-dimensional Monte Carlo light-scattering models are used to show that this may occur with a scattering geometry, which contains a dusty envelope surrounding the accretion disk as well as aligned grains. The detection of the large and extended CP in this source and the Orion supports the CP origin of the biological homochirality on Earth.
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[Speaker 2]
Anjali John K

[Title]
Association of Polar faculae with the Polar magnetic patches as observed by Hinode

[Abstract]
The polar region of the Sun, as observed with Hinode SOT/SP is found to be covered by patches that harbour strong magnetic field and that the large unipolar patches with flux > 10^18 Mx determine the polarity of the polar field. It is also observed that there are small
bipolar patches (< 1018Mx) with balanced flux in the polar region. The polar faculae, the small-scale bright magnetic structures observed at heliographic latitudes > 70 deg., have been considered as a good proxy for the polar magnetic field. The aim of this study is to understand the magnetic properties of faculae, which are believed to be associated with the polar magnetic patches. We analysed data of the north polar region taken by the Hinode/SOT- spectropolarimeter (SP) in September 2007. There are patches without faculae and they outnumber those with faculae. Faculae are present in all the patches with flux > 10^19 Mx. Magnetic patches are not uniformly bright but contain smaller faculae inside. We find that a positive correlation exists between total flux and intensity of faculae within the magnetic patches and that the faculae intensity depends on cosine of the heliocentric angle .

今年も例年通り、総合研究大学院大学/天文科学専攻の特別公開が、国立天文台の特別公開に合わせ2012/10/26～27の期間、共同で開催されました。天文科学専攻に所属する約30名の学生は、それぞれの所属部署と総研大の両方で準備を進めながら、当日は"総研大生の研究ライフ2012"と言う企画運営に携わりました。当日はお子さんから10～20代の若者、お子さんの親御さん世代の30~40代、更にはお孫さんがいらっしゃる50~60代の方々と幅広い年齢層の方々が来場されました。企画中にアンケートを取った結果（アンケート集計人数は263人）、"大学院での生活がどのようなものなのか、日常・非日常で分けていて、とてもイメージがつきやすかったです。非日常で、色んな観測所で観測をしているのが印象に残りました"と言うコメントを頂き、学生らしさが出た企画が好評を博していました。また、"（総研大の）存在を初めて知ったので、何もかもが印象的でした"と言うコメントなども頂き、総研大と言う存在を初めて知った方も多くいらっしゃったようです。総研大のPRを兼ねている特別公開なので、企画が持っている目標が十二分に達成されたと言えそうです。一方で、所属部署と総研大企画のシフト調整が直前まで行われていなかったり、折角上手に出来ている動画の配置場所が悪かったりと、反省点も挙げられています。来年の企画立案の際にはこれらの反省を活かし、更に良いものにして貰えればと思います。

毎年好評の総研大企画の景品や会場の様子！ クイズの景品は毎年豪華！ 学生の日常を紹介中！ クイズに正解すると、景品が貰えます！

文責：　総合研究大学院大学　天文科学専攻　博士過程4年　坂井 伸行

[Speaker 1]
Nobuyuki Sakai

[Title]
Absolute Proper Motion of CB 3 Away from the Galactic Plane Measured with VERA in a Galactic Superbubble

[Abstract]
TBA

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[Speaker 2]
Daehyun Oh

[Title]
Powerful high-contrast imaging techniques on direct detection of exoplnaets

[Abstract]
Direct detections of very faint exoplanets and brown dwarfs near bright stars are essential in understanding substellar for- mation and evolution around stars. The task is dauntingly difficult. The exoplanet or brown dwarf image is usually much fainter than the background from the brilliant PSF image. Aside from the Poisson noise, ground-based tele- scopes suffer from atmospheric turbulence that produces random short-lived speckles that mask faint companions. I will talk about two techniques called ADI and LOCI, can be used on ground-based altitude/ azimuth telescopes to subtract a significant fraction of the stellar quasistatic noise.

[Speaker 1]
Amnart Sukom

[Title]
Near-infrared Imaging Polarimetric Study of Orion A molecular cloud

[Abstract]
Orion Molecular Cloud (OMC) is the nearest region of massive star formation, which was intensively studied as a representative of star-forming regions. The northern part of Orion A molecular cloud,
OMC-1, -2, -3, and the southern part, OMC-4, are often referred to Integral Shape Filament (ISF), and contain intermediate-sized molecular cores, low and high mass young stars, dozens of Herbig-Haro (HH) objects and molecular outflows.
We present the first wide-field deep near-infrared images of 15' x 50' area of the Orion A ISF, obtained by SIRPOL, simultaneous JHKs imaging polarimeter on the IRSF telescope. Point-source aperture polarimetry suggest the magnetic field orientations are perpendicular to the elongation of the filament. Moreover, the hour-glassed shape magnetic field pattern in OMC-1 is confirmed by our polarization maps.
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[Speaker 2]
Takuya Suenaga

[Title]
Revealing the lower side of IMF and Searching for planetary mass objects

[Abstract]
Initial mass function (IMF) is one of the most important physical parameters in the star formation theory. Many author have investigated the IMF for a long time, however it has not been completely understood. I'm studying the lower side of IMF, in particular the bottom. Here, I'll introduce some studies related to IMF, and my ongoing works.

[Speaker 1]
Akimasa Kataoka

[Title]
Static compression process of dust aggregates in protoplanetary disks

[Abstract]
Planetesimal formation process in protoplanetary disks is a key issue in planet formation. Recently, internal density evolution of dust aggregates with collisional compression has been proposed to solve this problem (Okuzumi et al. 2012). However, other compression processes, which are caused by gas drag or self gravity, have not been considered. Such compression processes may differ from collisional compression processes, and thus it may greatly affect internal density evolution of dust aggregates. Therefore, we investigated static compression processes of porous aggregates by calculating N-body
simulation with considering direct interaction forces (Wada et al. 2007), and we determine the equation of state of porous aggregates.

[Speaker 1]
Takatoshi Shibuya

[Title]
Galactic-scale Outflow at z>4 revealed by Adaptive Optics

[Abstract]
Characterization of the large-scale galactic outflow is very important to understand many astrophysical phenomena at high-z, such as the escape of LyA photons from the galaxy, the relation between the galaxy populations, and IGM metal-enrichment history. Although galactic outflows are ubiquitously found in star-forming galaxies at 2 ------------------------------------------------------------------------------------------

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[Speaker 2]
Jun Toshikawa

[Title]
Spectroscopic Follow-up Observation of a High-redshift Protocluster Candidate

[Abstract]
Galaxy clusters play an important role in the large-scale structure of the universe and galaxy evolution.
Protoclusters, that are progenitors of galaxy clusters, would provide a great deal of information on the primordial condition at their birth.
However, it is difficult to discover them due to very low number density in the early universe, and only a few protoclusters were discovered currently.
In order to approach the question of cluster formation, we have to begin with searching other protoclusters.
We have carried out the survey of galaxy distribution at z~6 in the very wide field of the CFHT Legacy Survey Deep fields (~4 square degree),and found two protocluster candidates.
Subsequently, spectroscopic follow-up observation was conducted for one of the candidates with Gemini/GMOS.
Although there are some indication of a protoclsuter, we could not clearly confirm due to the small sample.
In the colloquium, we present the results of the follow-up observation.

[Speaker 1]
Junya Sakurai

[Title]
Measurement of Mass Distribution of Dark Matter Using Weak Gravitational Lensing

[Abstract]
According to the observational results from high-z supernovae and CMB, the universe almost consists of the dark matter and the dark energy.
Unfortunately, these components haven't entirely understood yet. To understand these unknown objects, some techniques are proposed. One of these techniques is the gravitational lensing. The gravitational lensing is the effect that the shape of the background galaxy is distorted by the foreground object. We can estimate the mass
distribution of the foreground object from the distortion of the background galaxy. Even if the foreground object is the dark matter, we can estimate the mass distribution of the dark matter. In my talk,
I present the gravitational lensing of the basis of this technique.
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[Speaker 2]
Rhythm Shimakawa

[Title]
Nature and Nurture Effects on the Formation and Evolution of Cluster Galaxies

[Abstract]
In low-redshift clusters, most galaxies appear to be quiescent.
These galaxies tend to be elliptical or S0 galaxies, which constitute conspicuous red-sequence on the color-magnitude diagrams.
In contrast, in high-redshift proto-clusers, galaxies tend to have complicated morphologies and high star-formation rates (SFRs) of 100s $M_\odot/yr$.
Such truncation in star formation activities can be caused by "nature" effects, i.e.\ accelerated galaxy formation in dense environments, and/or by "nurture" effects, i.e.\ galaxy-galaxy interactions/mergers and gas-stripping (e.g.\ Kodama et al. 2001).
Recent works (Daddi et al 2007; Mannucci et al. 2010) have presented double (main and sub) sequences of star forming galaxies on the SFR versus gas-mass plane, and a fundamental metallicity relation (FMR) where gaseous metallicity of star forming galaxies in the SDSS are determined as a function of stellar mass and SFR, both of which describe the modes of star formation and the evolutionary stages of galaxies.
Motivated by these observational phenomena, we now aim to explore these relationships (main/sub sequenes and FMR) in clusters/proto-clusters based on near-infrared specroscopy (FMOS/MOIRCS on Subaru) and ALMA observations (Mahalo-Subaru and Gracias-ALMA projects).
By comparing these relationships in clusters with the field counterparts, we will quantify the roles of environments to shape galaxies, and thus understand the origin of environmentally dependent galaxy formation and evolution.
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[Speaker 3]
Shogo Ishikawa

[Title]
the determination of the masses of dark matter halos by clustering properties of sBzK galaxies

[Abstract]
The existence of vast "dark matter halos" around luminous galaxies is strongly implied by some evidence. It is extremely difficult, however, to measure the masses of high-redshift galaxies' dark matter halos.
One method to quantify them is to measure the amplitude of galaxy clustering, since CDM models predict a monotonic correlation that more massive halos are clustered more strongly. Measuring galaxy clustering requires a large sample from wide area.However, it is still hard to do this at z~2, where BzK color selection can allow us to accumulate larger samples, due to a lack of combination of wide optical and NIR data. I will show our challenge to overcome this difficulty.
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[Speaker 1]
Zhao Zhengshi

[Title]
Spectroscopy of blue straggler stars in Galactic open cluster NGC 2682 (M67)

[Abstract]
In this presentation, we report spectroscopic analysis of eight blue straggler stars (BSSs) and three turn-off stars (TOs) in the old open cluster (OC) NGC 2682. From the high resolution (R~60,000) spectra obtained by the Subaru / HDS, we derived radial velocity, rotation velocity, and calculated chemical abundances of lithium, carbon and oxygen. Radial velocity of the target stars is consistent with the mean radial velocity of member stars of the cluster. Thus, we confirm the targets are indeed the real members of the cluster. Rotation velocity of BSSs distributes in a wide range of few km/s to hundred km/s, while those of TOs is restricted to a small value (vsini ≦7 km/s) . Both mass transfer scenario and collision scenario are expected to spin up BSSs. Target stars with measured Li abundances show a good agreement to the trend between A(Li) and Teff found in previous works . Moreover, BSSs have C and O abundances not significantly different from those of the TOs. Exceptions are BSS S997 and S1273. S997 shows a slight enhancement in O abundance, while S1273 shows a significant depletion in C abundance and a slight depletion in O abundance compared to other BSSs and TOs in the same cluster. These anomalies in C and O abundances may be interpreted by mass transfer scenario.
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[Speaker 2]
Cheul Hong Min

[Title]
VERA observations of SiO masers in Symbiotic star R Aquarii

[Abstract]
R Aquarii (R Aqr) is one of the closest symbiotic systems and one of the SiO maser sources associated with the Mira variable in Symbiotic star. These systems are very interesting target, and R Aqr is very exciting laboratory because of the existence of jet-like feature.
Though observations of the system have not yielded consistent values of the orbital parameters, the binary parameters of the orbit give an evidence whether or not Roche lobe outflow in the long period variable and interacting stellar winds of the formation of accretion disk and jet in secondary star. VERA has performed the observations toward R
Aqr since 2004. VERA its unique observation system is a powerful tool for astrometry, and we can hopefully obtain information about its orbital motions. In this presentation, I will present the result of VERA observations for R Aqr.

[Speaker 1]
Ayumu Matsuzawa
M2, SOKENDAI, Mitaka（supervisor : Satoru Iguchi）
[Title]
Evaluation of pointing error on ALMA ACA antenna

[Abstract]
The pointing error is difference between actual direction and directed direction of the antenna. I evaluate the activity of scientific performance by pointing error for ALMA antenna. The pointing error of ALMA antenna has three components: The components of antenna, the component of the optical pointing telescope and the components of the atmosphere. The purpose of my research is extract and evaluates the only component of radio antenna. Because, the component of antenna specification be established.
Therefore, the component of antenna can correctly evaluate rather than other two components.

For evaluate the pointing error, I estimate the pointing error from measurement data. The measurement of pointing error uses the optical pointing telescope (OPT). OPT installed in surface of antenna, and shooting a star by CCD in OPT. In the image of CCD, the pointing error assumed the difference center of image between centroid of star. But, this image included same noise. I made a program for remove the noise in image. I confirm that this program perform in ideal image as expected.

The component of antenna has some components (wind, thermal, servo, meterology). For extract these components, I measure the pointing error by Long tracking (measure the pointing error when tracking the one source over 15min). It can extract using the data of resolver and thermocouple. Now, I measure the pointing error by many long tracking, also I will measure the pointing error by Fast switching (measure the pointing error when the antenna is moving fast). After this, I will evaluate the component of radio antenna from pointing error. By this research, I expect improve the precision of pointing error for ALMA antenna.

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[Speaker 2]
Nagisa Shino
D1, SOKENDAI, Mitaka（supervisor : Mareki Honma）
[Title]
Testing the formation scenario of massive star by CH3OH maser

[Abstract]
Now classⅠ CH3OH maser is thought to be associated with outflow, while classⅡ CH3OH maser is thought to be associated with accretion disc.
If this is true, classⅠ CH3OH maser is expected to be distributed perpendicularly with respect to rotating disk.
Detecting (or rejecting) this will play a major role in understanding the scenario of massive star formation.
To do this, we plan to observe distributions of two classes of CH3OH masers with VLBI. For that purpose, first we have to look fortarget sources in which both of classes are detected.
We performed the single-dish observations of both classes of CH3OH maser using Nobeyama 45m and Yamagucchi 32m telescopes.
As a result, we discovered 89 sources detected in both classes.