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2016.4.4-4.10

   

4月5日(火)15:00~16:00  国立天文台野辺山談話会   野辺山観測所本館 輪講室
Apr 5 Tue   Nobeyama NAOJ Seminar       Rinko-shitsu, Main building, NRO

4月5日(火)15:15~16:15  JASMINEセミナー   講義室
Apr 5 Tue   JASMINE Seminar    Lecture Room

4月8日(金)13:30~15:00  太陽系小天体セミナー   院生セミナー室
Apr 8 Fri   Solar System Minor Body Seminar   Student Seminar Room, Subaru bldg.

4月8日(金)16:00~17:00  国立天文台談話会   大セミナー室
Apr 8 Fri   NAOJ Seminar          Large Seminar Room

詳細は以下をご覧下さい。

4月5日(火)

キャンパス
野辺山
セミナー名
国立天文台野辺山 談話会
定例・臨時の別
定例
日時
4月5日(火) 15:00 ~16:00
場所
野辺山宇宙電波観測所 本館 輪講室
講演者
中井 直正 氏
所属
筑波大学
タイトル
南極望遠鏡計画の進捗状況

Abstract
南極10mテラヘルツ望遠鏡に関しては、当初建設予定であった新ドームふじ基地の建設が当面困難であることが明らかになったので断念し、
内陸部にある既存の越冬基地である仏伊のコンコルデイア基地(ドームC)に変更し、仏伊側と交渉するとともに1月~2月に当該基地で実地調査を行い、
また現地エンジニアと共同で具体的な建設行程案を策定した。その状況を報告する。
30mテラヘルツ望遠鏡計画に関してはTMT後の次期大型計画とするための具体的な実現の方策(大規模輸送、大電力供給等)を国立極地研究所と検討開始した。
極地研究所としては日本の南極大型計画として積極的に推進する可能性も検討している。

連絡先
 名前:宮本祐介
 備考:テレビ参加可

4月5日(火)

キャンパス
三鷹
セミナー名
JASMINEセミナー
定例・臨時の別
臨時
日時
4月5日(火)15時15分から16時15分頃
場所
講義室
講演者
Payel Das
所属
オックスフォード大学
タイトル
Stellar haloes as probes of galaxy evolution
アブストラクト:
 Halo stars may have formed in situ, been flung out from further in, or accreted from neighbouring systems. The particular combination of processes is embedded in the phase-space and metallicity distributions of the stars, and therefore they serve as fossils of the halo’s formation history. To first order, haloes can be treated as collisionless equilibrium systems, and thus dynamical models can be used to shed light on the intrinsic distributions of the stars.
 I will report on dynamical models of the haloes of a sample of massive elliptical galaxies and our own Galaxy. Massive elliptical galaxies are embedded in hot X-ray emitting gas. Assuming hydrostatic equilibrium enables the derivation of total mass profiles from measurements of the pressure and temperature profiles of the gas. Combined with photometric and kinematic data extending to the outer halo, dynamical models reveal the structure of the orbits of the stars. In the case of the Milky Way, we have extended dynamical modelling methods to the domain of chemodynamical modelling to exploit the richer variety of datasets that provide 7-D or 8-D coordinates for individual halo stars (three positions, three velocities, metallicities, and possibly alpha-abundances). In these models, the dynamics of populations of stars depend on their chemistry, and therefore their origin. Using these methods we have been able to examine metallicity and age gradients in halo stars within the context of dynamically consistent models.

連絡先
名前:郷田直輝

4月8日(金)

Campus
Mitaka
Seminar
Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic
Regular
Date and time
8 April (Fri), 13:30-15:00
Place
Student Seminar Room, Subaru Bldg.
Speaker
Ryoko Ishikawa and CLASP team
Affiliation
NAOJ
Title
Comparison of Scattering Polarizations in Lyman-alpha and Si III lines -Implication of the operation of the Hanle Effect in Enhanced Network Regions-
Abstract
The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) has provided us with the enigmatic scattering polarization of the hydrogen Lyman-alpha line (121.57 nm) and Si III line (120.56 nm) with unprecedentedly high polarization sensitivity for the first time. The complicated properties of the scattering polarization (i.e., conspicuous spatial variations in Q/I and U/I at the spatial scales of 10″-20″ and the absence of the center-to-limb variation in the Lyman-alpha core), which cannot be explained by the currently available 1D and 3D atmospheric models, gives us the difficulty to differentiate the Hanle effect from the scattering polarization due to the local symmetry breaking.
To overcome this difficulty, we perform the comparison of polarization profile with different sensitivities to the Hanle effect (i.e., differential Hanle effect). For this purpose, we exploit the Lyman-alpha core with the Hanle critical field strength of 53 G, Lyman-alpha wing, which is insensitive to the Hanle effect, and Si III line with the critical field strength of 295 G. The intensity distributions in Si III show that the line formation height is located between Lyman-alpha core and wing (i.e., the upper chromosphere). We focus on the U/I signals in the bright regions where we are confident that the influence from the local symmetry breaking is small and it is very similar among these three lines. Then, we find two different types of these regions; one is the region where the signs of U/I signals are the same among these three lines and another is the region where the signs of U/I in Lyman-alpha core and Si III lines are opposite to that in Lyman-alpha wing.
The different sign between Hanle sensitive and non-sensitive lines could indicate the operation of the Hanle effect. Additional evidence of the operation of the Hanle effect is derived from the HMI magnetogram, and it is found that the regions with the change of the sign harbor the very strong photospheric magnetic fields corresponding to the enhanced network region. Based on these observations results, we conclude that the Hanle effect is operating, indicating the presence of magnetic field of ~50 G in the upper chromosphere and the transition region.

Facilitator
-Name:Shin Toriumi

4月8日(金)

キャンパス
三鷹
セミナー名
国立天文台談話会
定例・臨時の別
定例
日時
4月8日(金) 16:00-17:00
場所
大セミナー室
講演者
福島登志夫
所属
国立天文台
タイトル
「ダークマター・ディスクによる渦巻銀河M33の回転曲線の解釈」
     ”Rotation Curve of M33 Explained by Disc Dark Matter”
Abstract
We developed a numerical method to compute the gravitational field of an infinitely-thin axisymmetric disc with an arbitrary surface mass density profile. We evaluate the gravitational potential by a split quadrature using the double exponential rule and obtain the acceleration vector by numerically differentiating the potential by Ridders’ algorithm. The new method is of around 12 digit accuracy and sufficiently fast because requiring only one-dimensional integration. By using the new method, we show the rotation curves of some non-trivial discs: (i) truncated power-law discs, (ii) discs with a non-negligible center hole, (iii) truncated Mestel discs with edge-softening, (iv) double power-law discs, (v) exponentially-damped power-law discs, and (vi) an exponential disc with a sinusoidal modulation of the density profile. Also, we present a couple of model fittings to the observed rotation curve of M33: (i) the standard deconvolution by assuming a spherical distribution of the dark matter and (ii) a direct fit of infinitely-thin disc mass with a double power-law distribution of the surface mass density. Although the number of free parameters is a little larger, the latter model provides a significantly better fit. (Reference: Fukushima, T. 2016, MNRAS, 456, 3702)

連絡先
-名前: 松田 有一

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