月別アーカイブ: 2010年10月

Introduction of the Direct Imaging Method: which stars should we target?

【日時】10月20日(水) 10:30~12:00
【場所】国立天文台・三鷹 中央棟(北)1階 講義室
【発表者(敬称略)】高橋 安大(総研大 M2・三鷹、指導教員 : 田村 元秀)
【タイトル】Introduction of the Direct Imaging Method: which stars should we target?
長らく惑星と言えば太陽系内だけであったが、1995年の最初の系外惑星発見以降、人類は急速に系外惑星を発見してきた。
これまでに我々が発見した系外惑星の数は500近くにのぼり、系外惑星発見の時代から、統計的に系外惑星を科学する時代に入ったと言っても過言ではない。
しかしながら系外惑星を取り巻く科学には明らかにされていない事柄が多く、その形成、進化などは未だに謎に包まれている。
とりわけ、ホットジュピターやエキセントリックプラネットと呼ばれる、太陽系内惑星にはない姿の惑星がどのように出来たかには惑星軌道移動や相互作用モデルなどいくつかの仮説があり、今も議論がある。そこで我々のチームはこれらの仮説を検証するべく、SEEDSプロジェクトに参加しHiCIAOを用いて惑星の直接撮像を試みた。
今回はそのintroductionとpreliminaryな結果を紹介する。

Scattered Radiation Field and Local Magnetic Field of the Protostellar Clusters in NGC 2264

【日時】10月13日(水) 10:30~12:00
【場所】国立天文台・三鷹 中央棟(北)1階 講義室
【発表者(敬称略)】Kwon Jungmi(総研大 D1・三鷹、指導教員 : 田村 元秀)
【タイトル】Scattered Radiation Field and Local Magnetic Field of the Protostellar Clusters in NGC 2264
The NGC 2264 IRS 2 region in the Mon OB 1 cloud was observed in the near-infrared (IR) J, H, and Ks bands, and imaging polarimetry was performed.
Our polarization data revealed various infrared reflection nebulae (IRNe) associated with the central IR young star cluster NGC 2264 IRAS 12 S1 core and identified their illuminating sources, and revealed at least three infrared reflection nebula cluster (IRNCs).
In addition, 270 point-like sources w ere detected in all three bands.
The near-IR polarizations of these sources seem to be caused mostly by the dichroic extinction.
The mean polarization position angle of sources with P /δP 3 is about 68°, which is interpreted as the projected direction of the magnetic field in the observed region of the cloud.
The distribution of the polarization angle has a dispersion of about 27°.

Blue straggler stars in dwarf galaxies

【日時】10月6日(水) 10:30~12:00
【場所】国立天文台・三鷹 中央棟(北)1階 講義室
【発表者(敬称略)】Zhao Zhengshi(総研大 D2・三鷹、指導教員 : 有本 信雄)
【タイトル】Blue straggler stars in dwarf galaxies
Blue straggler stars (BSS) are located above and blue-ward of MS turn-off in a CMD of stellar clusters. They have been found in many stellar environments in observational studies during past 50 years.
Two different mechanisms of them are commonly believed nowadays: mass transfer in binary systems and stellar merger occurred through a direct stellar collision. The former might be dominant in lower density environments, whereas the later might be considered to mainly occur in high-density environments. The most studies on these objects are focus on the globular clusters because the dynamical environment of them could produce both of BSS formed by different mechanisms.
In recent years, researches for BSSs in dwarf spheroidal galaxies (dSphs) are increased. Considering dynamical environments of dSphs, BSSs in them should be mainly formed by mass transfer. The observed radial distributions of BSSs in several dSphs are consistent with model predictions for BSS formation by MT mechanism. More interestingly, a statistically significant anti correlation between the relative BSS frequency respect to HB stars and absolute magnitude is found in dwarf galaxies, it is similar to that observed in globular clusters. In this presentation, the previous studies on BSSs, involving with several observational properties will be introduced.
Meanwhile, our works of BSSs in dwarf galaxies based on data observed by Subaru telescope are also introduced.