カテゴリー: Tea Talk

May 28 Tue 15:00-16:00
Tea Talk
hybrid; Lecture Room and Zoom

May 29 Wed 14:30-15:30
ALMA-J seminar
hybrid; Room 102 in ALMA Building and Zoom

May 29 Wed 15:30-16:30
NAOJ Science Colloquium
hybrid; Large Seminar Room in Subaru Building and Zoom

詳細は下記からご覧ください。

=============== May 28 Tue===============

キャンパス：三鷹　野辺山 水沢 岡山 ハワイ
セミナー名：Tea Talk
定例・臨時の別：臨時
日時：5/28（火）15：00～16：00
場所：講義室＋Zoom
講演者：縣　秀彦、花山　秀和、大越　治
所属：天文情報センター
タイトル：大越治「メキシコ・マサトラン　雲を通した日食」
　花山秀和「日食遠征報告～サンサバ編～」
　縣秀彦「日食遠征報告～ダラス編～」
　（3名それぞれ10分程度のトークの後、総合討論）
世話人の連絡先：
-名前：藤田登起子

備考：
参加方法：講義室＋Zoom

=============== May 29 Wed===============

Campus: Mitaka
Seminar: ALMA-J seminar
Date and time: 2024 May. 29 (Wed.), 14:30-15:30 JST
Place: Room 102 in ALMA building / Zoom (hybrid)
Speaker: Zongnan Li
Affiliation: NAOJ

Title: Ring or no ring – Revisiting the Multiphase Nuclear Environment in our Neighbor M31
Abstract:
Nuclear rings, prevalent in barred galaxies, offer great insights into the processes of gas transport toward galactic nuclei. However, our understanding of a peculiar nuclear ring, which has long been recognized to exist in our neighbor galaxy M31, remains elusive. Here we present a comprehensive study of this multi-phase gas structure, originally revealed by its dust emission, based on newly acquired mapping of CO(1-0) and CO(3-2) lines and archival spectroscopic imaging of atomic hydrogen and warm ionized gas, along with custom numerical simulations. These multi-wavelength data together provide an unprecedented view of the surface mass density distribution and kinematics of the nuclear ring, which challenges it being a single coherent structure. In particular, the ring is found to display a significant asymmetry in its azimuthal mass distribution, with the neutral gas concentrated in the northwestern segment while the ionized gas prominent in the southeastern segment. The observed off-centered and lopsided morphology disfavors an interpretation of gas streamers or resonance driven solely by a barred potential known to exist in M31. In addition, the ring’s line-of-sight velocity distribution suggests a circular motion with the assumed planar ring inclined by ∼ 30◦ relative to the outer disk of M31, which implies an external torque probably induced by the recent close-in passage of M32. Our hydrodynamical simulations tracking the evolution of nuclear gas of M31 influenced by both a barred potential and an oblique collision of M32, reveal the natural formation of asymmetric spiral arms several hundred Myr after the collision, which may mimic a ring-like feature under appropriate viewing angles. Therefore, we suggest that M31’s nuclear gas structure, instead of being a genuine rotating ring, comprises transient, asymmetric spirals with a substantial tilt.

Facilitator
-Name: Yu Cheng

===============May 29 Wed==============

Campus: Mitaka
Seminar: NAOJ Science Colloquium
Date and time: 2024 May 29 (Wed.), 15:30-16:30 JST
Place: the large seminar room / Zoom (hybrid)

Speaker: Pete Kuzma
Affiliation: NAOJ (as a JSPS International Fellow)
Title: Extended Structure in Globular Clusters
Abstract:
Globular star clusters (GCs) are significant building blocks of the Milky Way’s (MW) Galactic halo. With typical ages of approximately 10 billion years, GCs are relics from the earliest stages of galaxy formation and are suggested to have contributed significantly to the halo assembly process. The current population of over 160 GCs may represent a mere fraction of the initial population of GCs, as the halo is rich in stars with chemical abundances suggesting they originate from GCs. An exciting development over the past 20 years has been the discovery that several MW GCs possess significantly extended structures, sometimes reaching out to a few hundred parsecs (corresponding to many half-mass radii). The types of features found range from axisymmetric tidal tails to large diffuse stellar envelopes. Such structures are indicative of mass loss, but our understanding of extended stellar structures, such as chemistry, kinematics and overall ubiquity, is currently incomplete apart from a very small sample. This is primed to change as upcoming large spectroscopic surveys commence and provide spatial coverage and depth that have been difficult to achieve until now. In this talk, I will explore the nature of extended GC structures and their role in the build-up of the Milky Way halo. I will explore before and after the Gaia revolution, both chemically and kinematically, and how future surveys will revolutionise our view of GCs and their peripheries.

Facilitator
-Name: Kazumasa Ohno
Comment: English

March 4 Mon 9:00-10:00
NAOJ Seminar
hybrid; Large Seminar Room in Subaru Building and Zoom

March 5 Tue 10:00-11:00
太陽系小天体セミナー
Zoom

March 5 Tue 15:00-16:00
Tea Talk
hybrid; Rinkoh Seminar Room and Zoom

March 6 Wed 14:30-15:30
ALMA-J seminar
hybrid; Room 102 in the ALMA building and Zoom

March 6 Wed 15:30-16:30
NAOJ Science Colloquium
hybrid; Large Seminar Room in Subaru Building and Zoom

March 8 Fri 16:00-17:00
NAOJ Seminar
hybrid; Large Seminar Room in Subaru Building and Zoom

詳細は下記からご覧ください。

=============== March 4 Mon ===============

Campus：Mitaka
Seminar：NAOJ Seminar
Regularly Scheduled/Sporadic：Sporadic
Date and time：March 4, 2024 9:00-10:00
Place：Zoom/Large Seminar Room (hybrid)

Speaker：Dr.Francisco (Paco) Colomer

Affiliation：Ministerio de Ciencia, Innovación y Universidades

Title：A voyage of discovery

Abstract: Along the last 30 years, I have been involved in many projects at
national, European and global levels. A personal voyage of discovery,
from my PhD on VLBI observations of maser emission, to the construction
of a 40-m radio telescope in Yebes, the direction of JIVE as central hub
of the European VLBI Network, to the set up of a Global VLBI Alliance.
Now back in Spain, taking care of European policy and research
infrastructures, at the Ministry of Science, Innovation and
Universities. All of it with a common background: love for knowledge and
international collaboration.

Facilitator
-Name：Fumitaka Nakamura

=============== March 5 Tue ===============

キャンパス：三鷹
セミナー名：太陽系小天体セミナー
定例・臨時の別：定例
日時：3月5日（火曜日）10時00分～11時30分
場所：zoom
講演者：長谷川均

世話人の連絡先
　名前：渡部潤一
　
備考：テレビ会議またはスカイプによる参加も可

=============== March 5 Tue===============

キャンパス：三鷹　野辺山 水沢 岡山 ハワイ
セミナー名：Tea Talk
定例・臨時の別：臨時
日時：3/5（火）15：00～16：00
場所：Zoom＋輪講室
講演者：林　左絵子さん
所属： TMTプロジェクト
タイトル： 宇宙とのふれあいのススメを推める
言語：日本語

世話人の連絡先：
-名前：藤田登起子

備考：
参加方法：Zoom

=============== March 6 Wed==============

Campus: Mitaka
Seminar: ALMA-J seminar
Date and time: March 6 (Wed) 14:30-15:30
Place: hybrid (room 102 in the ALMA building and Zoom)

Speaker: Ikki Mitsuhashi
Affiliation: Tokyo University/ NAOJ
Title: Dust-obscured star formation of the UV-selected galaxies at high-z

Abstract:
Abstract: We present the recent study about the dust continuum emissions of UV-selected star-forming galaxies at z~5 and z~6. The datasets are mainly composed of two ALMA programs, the ALMA Cycle 8 large program CRISTAL for z~5 and the multi-band observation program SERENADE for z~6. By utilizing the combination of the identification of high-z galaxies with optical telescopes and the follow-up observations with the Atacama Large Millimeter/submillimeter Array (ALMA), we measured the statistical properties of the spectroscopically-confirmed galaxies at z=4-6.5. We constrained the obscured fraction of the star formation (fobs), defined as SFR[IR]/SFR[UV+IR], spatial extent of the dust continuum, IR luminosities, the dust temperature, and the dust-obscured star formation rate density. Our constraints on Mstar-fobs relation support that the obscured fraction at the range of Mstar<10^10Msun does not show clear evolution from z=0-2.5, but may decrease at the range of Mstar>10^10Msun. For an individual view, the spread from an average Mstar-fobs relation (Δfobs) shows a possible correlation with the compactness of SF region and the spatial offset between UV and dust continuum at z~5. Typical dust continuum sizes are ~1.5 kpc, and appear to be about two times more extended than the UV continuum. Our results show a lower IRX value by ~1 dex at βUV~0, and support the shallow IRX-βUV relation suggesting a good agreement with the metal-poor nature of the high-z galaxies. Estimated redshift evolution of Tdust with the combination of the analytical models and some observational constraints on the metallicity (Z) and gas depletion timescale (tgas) indicates the gentle increase of Tdust at high-z is naturally explained by an ~0.6 dex increase in tgas and ~0.4 dex decrease of Z. The dust-obscured star formation exhibits 40-150% star formation in the bright-UV galaxies (MUV<-20 mag) compared with the dust-unobscured star formation at z=5-6. The dust-obscured star formation may have an important role owing to their contribution to total SFRD.

=============== March 6 Wed==============

Campus: Mitaka
Seminar: NAOJ Science Colloquium
Date and time: 2023 Mar. 6 (Wed.), 15:30-16:30
Place: the large seminar room / Zoom (hybrid)

Speaker: Aoto Yoshino
Affiliation: The University of Tokyo (M1)
Title: Formation of streamers by dense core collisions
Abstract:
Stars are formed by the gravitational contraction of dense cores in molecular clouds. In the classical model, a nearly axisymmetric core gravitationally collapses to form a disk around the protostar (e.g., Terebey et al. 1984). On the other hand, recent high-resolution observations of protostellar cores have often revealed non-axisymmetric, elongated flows of material falling into the disk, called streamers (Pineda et al. 2020; Valdivia-Mena et al. 2022). Per-emb-2 is a protostellar system located in the Perseus Molecular Cloud at 300 pc, and interferometric observations with ALMA and other instruments have revealed a large, carbon-chain molecule-rich streamer structure (Pineda et al. 2020). However, the origin of streamers is still unknown, and core collisions are one candidate. In this study, we investigate the collision process of cores using three-dimensional hydrodynamic simulations and explore the formation process of non-axisymmetric streamers that appear in the circumstellar structure.

Speaker: Hiroko Okada
Affiliation: University of Hyogo (D1)
Title: The origin of extremely metal-poor star with weak r-process signature
Abstract:
The origin of the rapid neutron-capture process is a major question in astrophysics. The clue to answer this question is the chemical abundance patterns of metal-poor stars, which are believed to reflect the nucleosynthesis yields of a single event. Recent observations propose two r-process classes: the “main r-process” for light and heavy elements and the “weak r-process” for lighter ones. Aoki et al. (2017) suggested to use abundance ratios of first-peak neutron-capture elements (Sr-Ag) in metal-poor stars to identify the origin of weak r-process nucleosynthesis. However, their sample is not necessarily extremely metal-poor, and some contamination of main r-process, and even s-process, is suspected. To clarify the weak r-process’s pure abundance pattern, we studied the extremely metal-poor star SMSS J022423.27-573705.1, with a high lower limit on [Sr/Ba] ratio (Jacobson et al., 2015). Analyzing near UV spectrum data from the VLT/UVES, we measured 26 elemental abundances including first-peak neutron-capture elements and determine Ba abundance. We also compare our results with the latest nucleosynthesis models.

Facilitator
-Name: Kazumasa Ohno

Comment: English

=============== March 8 Fri===============

Campus：Mitaka
Seminar：NAOJ Seminar
Regularly Scheduled/Sporadic：Regular
Date and time：March 8, 2024 16:00-17:00
Place：Zoom/Large Seminar Room (hybrid)

Speaker：渡邉恵理子　Eriko Watanabe

Affiliation：電気通信大学 The University of Electro-Communications(UEC)

Title：天体観測に向けた深層学習に基づく大気揺らぎ抑制シングルピクセルイメージング

Abstract: 天体観測や防災用の遠隔監視の場面において，高精度なイメージングシステムの要求は高い．しかし，これらの場面では時間的に変動する不均一な空間位相分布である大気ゆらぎの影響をうけ，光波が乱れるため，精度が低下する課題ある．
　近年，一般的な二次元撮像素子と比べ耐ノイズ性に優れるイメージング技術であるSingle-Pixel Imaging(SPI)が注目されている．SPIは，対象物体の反射光もしくは透過光と符号化パターンとの光相関信号を用いて解析的あるいは統計的に像を再構成する手法であり，微弱光でのイメージングや光検出器の帯域を選択することで可視域外でのイメージングが可能である．
我々のグループでは，SPIの再構成過程にノイズ耐性向上のDeep Neural Network(DNN)を導入することで，大気揺らぎを抑制できることをシミュレーションおよび実験により示してきた．本講演では，天体観測に向けた深層学習に基づく大気揺らぎ抑制シングルピクセルイメージングの研究開発に関して，Kolmogorov乱流理論に則った大気ゆらぎの生成と本イメージングシステムにおける耐性効果の評価，大気ゆらぎなどの実問題に応用する際の学習コスト課題を抑制するDNNの提案と評価，天体望遠鏡への搭載に向けたSPI光学実験基盤等に関して紹介する。

Facilitator
-Name：Fumitaka Nakamura