[Speaker1]
Yuzhu, Cui, SOKENDAI 3rd year (D1)(Supervisor: Mareki, HONMA,Kazuhiro, HADA,Hiroshi, NAGAI)

[Title]
M87 Jets Investigations with East Asian VLBI Network (EAVN)

[Abstract]
The radio galaxy M87 offers an privileged opportunity to probe the jet launching and formation scales thanks to the proximity and large mass of the central black hole. This makes M87 a prime target for the Event Horizon Telescope (EHT) along with SgrA*. In April 2017, M87 was for the first time observed by EHT+ALMA. This may allow the first imaging of the black hole shadow and jet-launching regions at scales of a few Schwarzschild radii. However, due to the sparse uv-coverage of the EHT, a proper interpretation of the EHT image (emission features surrounding the shadow) may require contemporaneous complementary observations at the lower frequencies that provides the higher fidelity jet images. Here we will report partial results from detailed EAVN 22/43GHz monitoring observations of M87 that were performed from January to May 2017 (so-called the “EAVN campaign 2017”), covering well the EHT-2017 observing window. We obtained data for a total of >15 epochs, and for each session 7-15 telescopes joined from East Asia, boosting the sensitivity and imaging capability compared to KaVA. These data will uniquely monitor the detailed structural evolution of the jet, velocity fields and possible component ejections near in time to the EHT period.

[Speaker1]
SAI Jinshi, D1 at the University of Tokyo(Supervisor: OHASHI Nagayoshi,,)

[Title]
Disk Structures around the Class I Protostar L1489 IRS Revealed by ALMA

[Abstract ]
We observed a Class I protostar, L1489 IRS with ALMA at high spatial resolutions of ~0.3” in ALMA Band 6 (230 GHz). Our new observations in C18O 2-1 emission allowed us to confirm that the Keplerian disk extends to ~600 au in radius. We also found a gap structure at a radius ~200-300 au on a disk in C18O 2-1, and that the gas disk of L1489 IRS consists of two disks, an inner disk extending to ~200 au and an outer disk extending to ~300-600 au in radius. Furthermore, it was found that the inner disk and outer disk are misaligned by ~15 deg by comparison between observations and a kinematic model of a Keplerian disk. This misaligned disk system suggests that the axis of angular momentum of an accretion changes its direction during the star and circumstellar disk formation process. 1.3 mm dust continuum extends to ~ 370 au continuously however a gap structure is seen in C18O. It infers that the gap in C18O is due to CO depletion but the origin of the C18O gas gap is still on debated.

[Speaker2]
Jungha Kim, SOKENDAI 4th year (D2)(Supervisor: Mareki Honma,Tomoya Hirota,Katsunori Shibata)
[Title]
Dynamics of jets/outflows from high-mass young stellar objects revealed by KaVA and ALMA observations

[Speaker1]
Tadafumi Matsuno, SOKENDAI 4th year (D2)(Supervisor: Wako Aoki,Yutaka Komiyama,Takuji Tsujimoto)

[Title]
The first chemo-dynamical view of very metal-poor stars

[Abstract]
The second data release of Gaia (Gaia DR2) enables us to explore motions of a large number of stars in the Milky Way. Maximum scientific output would be obtained by complimenting the Gaia data set with stellar chemical abundances, since stellar motions tell us about past dynamical interactions between Milky Way and satellite galaxies whereas chemical abundances tell us about past star formation activities. To understand the formation history of the Galactic stellar halo, one of the oldest structures in the Milky Way, we have crossmatched the SAGA database, which complies results of abundance measurements for very metal-poor stars in literatures, to the Gaia DR2 catalog. In this talk, after describing the procedure of the crossmatch, I will introduce the latest results from the first chemo-dynamical analysis of very metal-poor stars.

[Speaker2]
Satoshi Kikuta, SOKENDAI 4th year (D2)(Supervisor: Masa Imanishi,Yuichi Matsuda,Yutaka Komiyama)

[Title]
Lyman alpha imaging around a hyperluminous QSO at z=2.84 with HSC

[Abstract]
We present the results of our Lyα imaging around a hyperluminous QSO, HS1549+1919, at z=2.84 with Hyper Suprime-Cam (HSC). Thanks to the HSC’s overwhelmingly large FoV, we detected >3000 Lyα emitters (LAEs) in diverse environments within a 1.1 deg^2 FoV. The QSO is confirmed to reside in the very center of a protocluster and is surrounded by a ~1pMpc-scale diffuse Lyα nebula. The EW distribution and properties of Lyα halos are studied as a function of environments. At the center, extreme objects such as QSOs, LABs, and SMGs are far more abundant than fields, suggesting a large amount of gas is accreting towards the center.

[Speaker1]
Yongming Liang, SOKENDAI 1st year (M1)(Supervisor: Nobunari Kashikawa (U.Tokyo),Masayuki Tanaka,Yuichi Matsuda)
[Title]
Search for massive overdensities at z~2.2 with Subaru HSC

[Speaker2]
Masaki Yoshida, SOKENDAI 4th year (D2)(Supervisor: Yoshinori Suematsu,Hirohisa Hara,Ryohko Ishikawa)
[Title]
Wave-front error measurements and optical alignment of CLASP2 telescope

　2018年5月19日（土）、国立天文台三鷹キャンパスにおいて、特別公開講演および総研大入試ガイダンスが行われました。本年も学部１年生の方から大学院生まで、総勢54名の方々にご来場いただきました。

　今年度は『国立天文台における天文学研究の最前線』テーマに、片岡章雅助教、田中賢幸准教教、大石雅寿准教授、松本晃治准教授の４名の先生方から、それぞれの分野の視点に立った興味深いご講演をいただきました。今年度は大学1年生の参加者が例年に比べ多く、大学に入ったばかりにもかかわらず、大学院へ進学することを考えている意識の高さに感心しました。講演の後の質問の時間には、一般的な天文学に関するものから非常に専門性の高いものまで、多くの質問がありました。
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