カテゴリー: ALMA Jセミナー

November 　21 Tue 10:00-11:30 太陽系小天体セミナー zoom　　　　　　　　　　　　　　

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November 　21 Tue 14:30-15:30 ALMA-J seminar Seminar room in the Subaru building (院生セミナー室) / Zoom (hybrid)

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November　22 Wed 10:30-12:00 SOKENDAI Colloquium Large Seminar Room in Subaru Building and Zoom

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November　22 Wed 15:30-16:30 NAOJ Science Colloquium the large seminar room / Zoom (hybrid)

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November 24 Fri 16:00-17:00 NAOJ Seminar Zoom/Large Seminar Room(hybrid)

詳細は下記からご覧ください。

=============== November 　21 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：11月21日（火曜日）10時00分～11時30分
場所：zoom
講演者：大島修（岡山理科大学）・藤井貢（藤井黒崎観測所）
タイトル：イオ周辺の中性ナトリウム雲の活動
Abstract：木星の衛星イオに関連したナトリウム雲の非常に活発な活動を観測したので報告する。藤井は、今年10月始めから口径13cm屈折望遠鏡にNaI D1
D2狭帯域フィルター（半値幅2.3nm）をかけて、木星の衛星イオの周辺を撮像観測している。イオからのナトリウム雲は、当初、軌道平面とは角度を持った方向へ噴出したものが、その後軌道平面方向に広がり、一部にねじれを持ったりしながら拡散しているように見える。一体どのような現象を見ているのか議論に供したい。

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

=============== November 　21 Tue===============

Campus: Mitaka
Seminar: ALMA-J seminar
Date and time: Nov 21 (Tue) 14:30-15:30
Place: Seminar room in the Subaru building (院生セミナー室) / Zoom (hybrid)
Speaker: Amanda Kepley (NRAO)

Title: Next Steps Towards Understanding Star Formation: Mapping Dense Gas in Nearby Galaxies
Abstract:
From both a theoretical and an observational perspective, dense gas plays an important role in star formation. Almost all theories of star formation have gas density as a key variable, while observations in the Milky Way and nearby galaxies suggest a close link between dense gas and star formation. Early unresolved observations of nearby galaxies suggested a simple relationship between the amount of dense gas and the amount of star formation in a galaxy. Recent resolved surveys of dense molecular gas in nearby galaxies, however, have shown that the dense gas fraction and the dense gas star formation efficiency ? ratio of the star formation rate to amount of dense gas ? varies within individual galaxies and among different galaxies. Unfortunately, the faintness of the primary dense gas tracers (HCN and HCO+) mean that these studies have been limited to small (5-10) samples of normal galaxies. In this talk, I will discuss recent observations that push the dense molecular gas observations in new directions. First, I will describe recent detections of dense molecular gas in the Local Group Dwarf starburst IC 10. Second, I will present early results from the Dense Extralactic GBT+Argus Survey (DEGAS). The goal of this survey is to map the dense molecular gas in the central 2arcmin of 36 nearby galaxies at moderate (10arcsec) resolution. I will conclude with thoughts on how a large mm cameras on single dish telescopes and more sensitive interferometers could further advance this important science.

Organizers: Gianni Cataldi, Hiroshi Nagai

=============== November　22 Wed==============

Campus：Mitaka
Seminar：SOKENDAI Colloquium
Regularly Scheduled/Sporadic：Regular
Date and time：November 22, 2023 10:30-12:00
Place：Large Seminar Room in Subaru Building and Zoom

Speaker: Shotaro Tada
Affiliation: SOKENDAI 4th year (D2) (Supervisor: Takayuki Kotani, Yutaka Hayano, Yosuke Minowa)
Title: InGaAs Detector Testing for JASMINE: Efforts to Minimize Readout Noise & Dark Current Measurement

Speaker: Ko Hosokawa
Affiliation: SOKENDAI 45h year (D3) (Supervisor: Takayuki Kotani, Yosuke Minowa, Yuka Fujii)
Title: Spectral Line Profile Measurement for Investigating Gas-giant Atmospheres

Facilitator
-Name：Matsuda, Graduate Student Affairs Unit

=============== November　22 Wed==============

Campus: Mitaka
Seminar: NAOJ Science Colloquium
Date and time: 2023 Nov. 22 (Wed.), 15:30-16:30
Place: the large seminar room / Zoom (hybrid)

Speaker: Jihye Hwang
Affiliation: KASI
Title: The distribution of magnetic field strengths in star-forming regions
Abstract:
“What is the role of magnetic fields for regulating star-forming processes?” It is a long- standing issue in star formation studies. To judge the exact role of magnetic fields in star-forming regions, it is necessary to estimate the magnetic field strengths of those regions.
However, previous studies have estimated a mean magnetic field strength in a whole star-forming region. I suggest a new application to estimate the distribution of magnetic field strengths in a star-forming region. I applied this towards three star-forming regions, the OMC-1 region, Mon
R2 and G28.34 using POL-2/SCUBA-2 on the James Clerk Maxwell Telescope.
In this talk, I will show the magnetic field strengths in those regions and discuss the relative importance between magnetic field, turbulence and gravity.

Facilitator
-Name: Doris Arzoumanian
Comment: English

=============== November　24 Fri==============

Campus：Mitaka
Seminar：NAOJ Seminar
Regularly Scheduled/Sporadic：Regular
Date and time：November 24, 2023 16:00-17:00
Place：Zoom/Large Seminar Room (hybrid)

Speaker：Prof,Aya Ishihara
Affiliation：Chiba University

Title：ニュートリノを基軸とした宇宙のマルチメッセンジャー観測
Abstract:
高エネルギー宇宙ニュートリノは、宇宙のどこかで加速されている超高エネルギー宇宙線が天体内外の光や物質と相互作用することで生成される荷電パイオンの崩壊によって作られる。
同時につくられる中性パイオンの崩壊からはガンマ線が出るので、ニュートリノ天文学と言う時は通常光を使った観測と組み合わせ、マルチメッセンジャー天文学として統合的な宇宙理解を目指す。
特に、ニュートリノは天体内外の加速の現場からの情報を直接伝えてくれるので、粒子加速モデルの鍵となる情報をもたらすことが期待されている。また、ニュートリノのマルチメッセンジャー観測は、ダークマターや標準模型を超える物理に迫る観測をも可能とする。
このような高エネルギー宇宙ニュートリノの観測目指し南極点に建設されたのが世界初となる一立方キロメートルの容量を持つIceCubeニュートリノ望遠鏡だ。本講演ではIceCubeの完成から約10年で得られた成果を紹介し、その成果を踏まえた将来展望について議論する。

Facilitator
-Name：Okamoto, Takenori

November 　14 Tue 10:00-11:30 太陽系小天体セミナー zoom　　　　　　　　　　　　　　

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November 　15 Wed 10:30-12:00 SOKENDAI Colloquium Large Seminar Room in Subaru Building and Zoom 　　

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November　15 Wed 14:30-15:30 ALMA-J seminar Small seminar room in Subaru building (院生セミナー室) / Zoom (hybrid)

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November　15 Wed 15:30-16:30 NAOJ Science Colloquium Zoom (full virtual style)

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詳細は下記からご覧ください。

=============== November 　14 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：11月14日（火曜日）10時00分～11時30分
場所：zoom
講演者：野上長俊

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

=============== November 　15 Wed===============

Campus：Mitaka
Seminar：SOKENDAI Colloquium
Regularly Scheduled/Sporadic：Regular
Date and time：November 15, 2023 10:30-12:00
Place：Large Seminar Room in Subaru Building and Zoom

Speaker: Yoshihiro Naito
Affiliation: SOKENDAI 2nd year (M2) (Supervisor: Hirohisa Hara. Ryoko Ishikawa, Joten Okamoto)
Title: Spectroscopic study of Alfvén waves in the upper chromosphere as an energy source of solar wind acceleration in coronal holes

Speaker: Yoshiaki Sato
Affiliation: SOKENDAI 2nd year (M2) (Supervisor: Noriyuki Narukage, Takashi Sekii, Masumi Shimojo)
Title: Evaluation of electron acceleration efficiency during solar flares using MHD+GCA Test-Particle simulation

Facilitator
-Name：Matsuda, Graduate Student Affairs Unit

=============== November　15 Wed==============

Campus: Mitaka
Seminar: ALMA-J seminar
Date and time: Nov 15th (Wed) 14:30-15:30
Place: Small seminar room in Subaru building (院生セミナー室) / Zoom (hybrid)
Speaker: Mengyuan Xiao
Affiliation: University of Geneva
Title: A new era of studying extremely dust-obscured massive galaxies in the early Universe with JWST and ALMA
Abstract:
Recent studies have unveiled the existence of extremely dust-obscured massive galaxies at z>3 and into the reionization epoch. This has significant implications for our understanding of early galaxy build-up and the cosmic star formation history. In this talk, I will discuss our recent findings on these galaxies with JWST FRESCO survey and GOODS-ALMA survey. In particular, I will present the advantages of JWST/spectroscopy in studying these galaxies. Based on the unprecedented imaging and spectroscopic data from the JWST FRESCO survey, we can systematically determine their spectroscopic redshifts, thus vastly improving constraints on their physical properties. In addition, I will show several extremely massive dusty galaxies at zspec > 5, that may challenge the current galaxy assembly models. I will discuss their ultra-massive properties, dust-obscured star formation rates, and the possibility of the existence of AGN. I will finish with some of our other recent discoveries and future plans for extremely dust-obscured massive galaxies.

Organizers: Gianni Cataldi , Hiroshi Nagai

=============== November　15 Wed==============

Campus: Mitaka
Seminar: NAOJ Science Colloquium
Date and time: 2023 Nov. 15 (Wed.), 15:30-16:30
Place: Zoom (full virtual style)

Speaker: Aya Bamba
Affiliation: The University of Tokyo
Title: X-ray study of supernova remnants, the origin of diversity in the universe

• 多様性の源: 超新星残骸のX線研究 –
  Abstract:
  Supernova remnants (SNRs) supply thermal and kinetic energy, heavy elements, and high energy particles (cosmic rays) into the space, so they are the origin of diversity of the universe. Shocked plasma is heated up to 1-10 MK, and emits thermal X-rays with characteristic X-ray lines from heavy elements, thus X-ray observations are an ideal tool how SNRs play their role in the universe. In this talk, I will introduce several recent topics of SNR science – progenitor science and shock physics.
  Such a study needs excellent energy resolution in the X-ray band in order to resolve emission lines from minor elements and their Doppler motion. On this September, we succeeded to launch XRISM with H2A rocket.
  I also introduce how XRISM is launched and what XRISM will achieve on SNR science.

Facilitator
-Name: Hiroki Nagakura
Comment: English

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October　31　Tue　 　10:00-11:30　　太陽系小天体セミナー　　　　Zoom
　　　　　　　　　　　　　　　　　　　　

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October　31　Tue　　15:30-16:30 　　 NAOJ Seminar　
　　　　　　　　　　　　　　　　　　　Zoom/Large Seminar Room (hybrid)　　　　　　　　　　　　　

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November　1　Wed　10:30-12:00 　　SOKENDAI Colloquium　
　　　　　　　　　　　　Large Seminar Room in Subaru Building and Zoom

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November　1　Wed　14:30-15:30　　 ALMA-J seminar 　
　　　　　　　　　　　　hybrid (ROOM102 in ALMA building and ZOOM)

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November　1　Wed　15:30-16:30　　 NAOJ Science Colloquium 　
　　　　　　　　　　　　　　the rinkoh seminar room / Zoom (hybrid)

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November　2　Thu　11:00-12:00 　　Tea Talk　　　　　　　Zoom

詳細は下記からご覧ください。

=============== October 　31　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：10月31日（火曜日）10時00分～11時30分
場所：zoom
講演者：藤井大地

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

=============== October 　31　Tue==============

Campus：Mitaka
Seminar：NAOJ Seminar
Regularly Scheduled/Sporadic：Regular
Date and time：October 31, 2023 15:30-16:30
Place：Zoom/Large Seminar Room (hybrid)

Speaker：Ruobing Dong, PhD
Affiliation：University of Victoria

Title：Observational Planet Formation
Abstract:
It is hard to see a plane cruising at 10 km during daytime, as the plane is
tiny and faint on the sky. But, if we can see the contrail tailed behind the
plane, we know where the plane is. Now, astronomers are applying the same
principle to study how planets form, by detecting and charactering the
structures baby planets produce in their birth cradles – protoplanetary
disks. This is a new field largely driven by discoveries made by some of the
largest and most advanced telescopes ever built. I will introduce the
current status of the field, and highlight some of the latest developments
as well as unsolved problems.

Facilitator
-Name：Prof. Nomura, Hideko

=============== November　1　Wed==============

Campus：Mitaka
Seminar：SOKENDAI Colloquium
Regularly Scheduled/Sporadic：Regular
Date and time：November 1, 2023 10:30-12:00
Place：Large Seminar Room in Subaru Building and Zoom

Speaker: Ryota Hatami
Affiliation: SOKENDAI 1st year (M1) (Supervisor: Nozomu Tominaga, Tomoya Takiwaki, Koh Takahashi)
Title: Synthesis of Sc, Ti, and V in core-collapse Supernovae toward constraining explosion mechanism

Speaker: Masato Sato
Affiliation: SOKENDAI 4th year (D2) (Supervisor: Nozomu Tominaga, Tomoya Takiwaki, Takashi Moriya)
Title: Exploring electron-capture supernovae in past observations

Facilitator
-Name：Matsuda, Graduate Student Affairs Unit

=============== November　1　Wed==============

Campus: Mitaka
Seminar: ALMA-J seminar
Date and time: Nov 1st (Wed) 14:30-15:30
Place: hybrid (ROOM102 in ALMA building and ZOOM)
Speaker: Ceci Xue
Affiliation: MIT
Title: Molecular Spectra Diagnostics with a Bayesian MCMC Approach
Abstract:
The recent improvement in receiver technology within modern facilities has enabled us to efficiently perform wide-band and high-sensitive molecular line surveys. To better extract the information from these wide-band spectral data, we introduce a molecular signal diagnostic tool coupling a non-LTE radiative transfer model and a Markov Chain Monte Carlo (MCMC) approach. Based on RADEX (van der Tak et al. 2007), our tool features novel implementations to support multiple components along the line of sight and allow Bayesian inference about physical characteristics. In contrast to a canonical least-squares fit approach, MCMC analyses allow a more efficient exploration of the physical parameter space and provide access to the parameter’s probability distribution, which can be used to characterize the confidence intervals and covariances between parameters. In this talk, following a brief introduction to Bayesian statistics, we will present a case study demonstrating the analysis of molecular line observations from ALMA using this tool. Specifically, we will share the first detection and mapping of the Class I methanol maser at 84 GHz toward the north region of Sagittarius B2 molecular cloud. We resolved the regions where the maser emission originates and assessed their observed spectral profiles respectively. The results suggest a chained two-component model for explaining the intense methanol Class I maser emission toward a region with weak continuum background radiation. In addition, our diagnostic tool will be applied to the spectral line survey, GOTHAM, which has a total bandwidth of 25GHz, to conduct the full chemical census toward the TMC-1 dark cloud.

Organizers: Gianni Cataldi, Hiroshi Nagai

=============== November　1　Wed==============

Campus: Mitaka
Seminar: NAOJ Science Colloquium
Date and time: 2023 Nov. 1 (Wed.), 15:30-16:30
Place: the rinkoh seminar room / Zoom (hybrid)

Speaker: Biagio De Simone
Affiliation: UNISA
Title: An Optical Gamma-Ray Burst catalogue with Measured Redshift: Data Release of 533 Gamma-Ray Bursts and colour evolution
Abstract:
Gamma-Ray Bursts (GRBs) are incredibly energetic cosmic phenomena observed across a wide range of wavelengths, including gamma-ray and optical frequencies, and occasionally even in radio waves. They allow extending the Hubble diagram and the cosmological analysis up to redshift z=9.4, much further than Supernovae Ia (z=2.26).
We therefore present a compilation of 533 optical lightcurves (LCs) of all GRBs with measured redshifts, detected mainly by Swift and 418 ground-based telescopes from February 28, 1997, to April 14, 2023. This catalogue is the largest optical repository of GRB LCs with redshifts to date, with 64615 photometric data points, including upper limits. Our user-friendly web tool, grbLC, allows the acquisition of GRB LCs, including information on the position, redshift, and a Gamma-ray Coordinates Network (GCN) crawler that can be used to collect data by gathering magnitudes from the GCNs. The web tool also includes a package for uniformly investigating colour evolution. We have crafted a procedure to distinguish between GRBs in our sample, which undergo colour evolution, and GRBs for which no colour evolution is present. We compared our results with the literature. This web-based archive is the first step towards unifying several community efforts to gather optical LCs by providing a unified format and repository for the optical catalogue. This catalogue will enable population studies by providing LCs with better coverage since we have gathered data from different ground-based locations, resulting in fewer gaps in the LCs and representing crucial support for the LC reconstructions analysis.

Speaker: Chanoul Seo
Affiliation: NAOJ
Title: Impact of Magma Redox States on Super-Earth Atmospheres:
Unveiling the Connection with Atmospheric Composition
Abstract:
Most exoplanets with radii larger than ~1.6Earth mass are more inflated than bare-rock planets with the same mass, indicating a substantial amount of volatile. While it is hard to constrain the origin of the volatiles or the planet’s bulk composition only from the mass-radius relation, the spectral characterization of their atmospheres is expected to solve this degeneracy. Previous models pointed out that the interaction between the accreted volatile and the likely molten rock (i.e., magma) beneath the atmosphere would affect the atmospheric composition significantly. However, existing models do not clarify the dependence of the atmospheric compositions with major spectral fingerprints on the observable planetary parameters. In this work, we explore the possible range of H, O, and C in the atmosphere of exoplanets as a function of observable planetary parameters (mass, radius, equilibrium temperature) using a simple chemical equilibrium model. Consistent with the previous work, we show that the water fraction in contact with magma ocean is the order of 10^-2~10^-1 if the dry planetary core accretes the nebula gas. Due to the difference in solubility of H-bearing and C-bearing species in molten rock, C/H shows an increase of ×3~10^2. The low values correspond to H2-rich atmospheres while the high values (the order of magnitude difference) correspond to the thin atmosphere with pressure <10^3 bar. Therefore, the C/O remains relatively low in most of the parameter range considered, below one-tenth of the nebula gas value if the atmospheric H2O fraction is over five percent. These trends provide a clue to verify or falsify the formation scenario of super-Earth/sub-Neptune from atmospheric compositions.

Facilitator
-Name: Maria Giovanna Dainotti
Comment: English

=============== November　2　Thu==============

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：11/2（木）11：00～12：00
場所：Zoom（のみ）
Speaker:Hannah Harris
Title:
International Scientific Cooperation with North Korea: from Ancient Astronomy to Today

Abstract:
The Korean Peninsula is home to an ancient and unique tradition in astronomy. Beginning with the prehistoric Stone Age and blossoming over the last two thousand years, astronomy is deeply enmeshed in Korean culture. It is unsurprising that North Korea, just like its neighbor to the South, continued this scientfic tradition. Yet astronomy and science in North Korea is still relatively unknown and understudied. Today, North Korean scientists are active participants in the international scientific community across many fields and disciplines. This talk presents the history and future prospects for international scientific cooperation with North Korea with an emphasis on astronomy.

Short bio:
Hannah Harris is a Canadian-American science communicator, researcher, and a current Marie Sklodowska-Curie Fellow with the International Atomic Energy Agency (IAEA). She has a Bachelor’s degree in Astrophysics from Wellesley College (USA) and researched spinning black holes at the MIT Center for Theoretical Physics and the Gravitational Physics Group at Cardiff University (Wales, UK). Recently, she finished a dual-degree masters program between Russia and the United States, where she studied nuclear physics, nuclear energy, and nuclear weapons, as well as international relations. Her thesis focused on scientific research in North Korea and the possibilities for nuclear risk reduction through peaceful scientific cooperation. Since 2014, she has collaborated with the IAU on a variety of space policy and outreach projects and served as the project manager for the “Inclusive Astronomy” programme during the IAU100 centennial celebrations in 2019.

世話人の連絡先：
-名前：藤田登起子
参加方法：Zoom

Oct 17 Tue 　10:00-11:30 　 太陽系小天体セミナー Zoom

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Oct 17 Tue 　13:30-14:30 NAOJ Seminar zoom/ Large seminar room in Subaru Building

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Oct 18 Wed 　10:30-12:00 　 SOKENDAI Colloquium Hybrid;Large Seminar Room in Subaru Building and Zoom

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Oct 18 Wed 　14:30-15:30 ALMA-J seminar hybrid (ROOM102 in ALMA building and ZOOM)

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Oct 18 Wed　 15:30-16:30 NAOJ Science Colloquium The large seminar room / Zoom (hybrid)

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詳細は以下をご覧下さい。

=============== October　17　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：10月17日（火曜日）10時00分～11時30分
場所：zoom
講演者：藤原康徳

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

=============== October　17　Tue===============

Campus：Mitaka
Seminar：NAOJ Seminar
Regularly Scheduled/Sporadic：Regularly Scheduled Date and time：2023 Oct 17, 13:30-14:30
Place：zoom/ Large seminar room in Subaru Building

Speaker：Dr,Bruno Dias
Affiliation: President, Sociedad Chilena de Astronomía (SOCHIAS) Professor, Institute of Astrophysics, Department of Physics, Faculty of Exact Sciences, Universidad Andrés Bello (UNAB), Chile

Title:　The Chilean Astronomical Society (SOCHIAS)

Abstract: The Chilean Astronomical Society (SOCHIAS) was founded on May 31, 2000 with the goals of boosting Astronomy in Chile, managing the interests of Chilean astronomers, organising scientific meetings, establishing and maintaining contact with organizations in Chile and abroad, and supporting Astronomy education, among other related objectives. In this context, two representatives of the current SOCHIAS board are visiting Japan, and in this presentation we will show some information about SOCHIAS as well as some of our initiatives. We hope to keep and strengthen the relationship among Japanese and Chilean astronomical communities.

Facilitator
-Name：Izumi Takuma

=============== October　18　Wed===============

Campus： Mitaka
Seminar： SOKENDAI Colloquium
Regularly Scheduled/Sporadic：Regular
Date and time：October 18, 2023 10:30-12:00
Place： hybrid; Large Seminar Room in Subaru Building and Zoom

Speaker: Moka Nishigaki
Affiliation: SOKENDAI 3rd year (D1) (Supervisor: Masami Ouchi, Tadafumi Takata, Kimihiko Nakajima)
Title: Modeling the Mass-Metallicity Relation with Dark Matter Halo Assembly from z=0–10

Speaker: Kuria Watanabe
Affiliation: SOKENDAI 2nd year (M2) (Supervisor: Masami Ouchi, Nozomu Tominaga, Masato Onodera)
Title: The Chemical enrichment and origin of Nitrogen-Rich Galaxies at High Redshift

Facilitator
-Name：Matsuda, Graduate Student Affairs Unit

=============== October　18　Wed===============

Campus: Mitaka
Seminar: ALMA-J seminar
Date and time: Oct 18th (Wed) 14:30-15:30
Place: hybrid (ROOM102 in ALMA building and ZOOM)

Speaker: Pei-Ying Hsieh
Affiliation: NAOJ

Title:The circumnuclear disk revealed by ALMA – environments of star formation in the inner 10 pc of the Galaxy

Abstract:The molecular 2-pc circumnuclear disk (CND) immediately around the Milky Way supermassive black hole (SMBH), SgrA, resembles the “molecular torus” in AGNs, providing a unique opportunity to study SMBH accretion and nuclear star formation at sub-parsec scales. In recent years, I have been studying the key question of how much of the available gas can actually form stars in the environment around Sgr A, and how material is being moved around and accreted in this region. The lifetime of the CND has been a long-standing debate over the past decade. The CND can not live longer than 10^5 years if the gas density is under the tidal threshold of SgrA/nuclear star clusters, thus depleting the source of fuel and star formation. Utilizing the ALMA and various single-dish telescopes, we present CS line maps toward the CND of the Galactic Center. Our primary goal is to resolve the compact structures within the CND and the streamers, in order to understand the stability conditions of molecular cores in the vicinity of Sgr A. Our data provide the first homogeneous high-resolution (1.3″ = 0.05 pc) observations aiming at resolving density and temperature structures. A stability analysis based on the unmagnetized virial theorem including tidal force shows that 84 (+16/-37) % of the total gas mass (2.5X10^4 Msun) is tidally stable, which accounts for the majority of gas mass. Turbulence dominates the internal energy and thereby sets the threshold densities 10-100 times higher than the tidal limit at distance >1.5 pc to Sgr A*, and therefore, inhibits the clouds from collapsing to form stars near the SMBH.

Organizers: Gianni Cataldi , Hiroshi Nagai

=============== October　18　Wed===============

Campus: Mitaka
Seminar: NAOJ Science Colloquium
Date and time: 2023 Oct. 18 (Wed.), 15:30-16:30
Place: The large seminar room / Zoom (hybrid)

Speaker: Yoshiaki Misugi
Affiliation: NAOJ

Title: Evolution of the Angular Momentum of Molecular Cloud Cores in Filamentary Molecular Clouds

Abstract:
The angular momentum of molecular cloud cores plays a key role in the star formation process. However, the evolution of the angular momentum of molecular cloud cores formed in magnetized molecular filaments is still unclear. We perform three-dimensional magnetohydrodynamics simulations to reveal the evolution of the angular momentum of molecular cloud cores formed through filament fragmentation. As a result, we find that the angular momentum decreases by 30% and 50% at the mass scale of
1 Msun in the case of weak and strong magnetic field, respectively. By analyzing the torques exerted on fluid elements at different mass scales, we identify the magnetic tension as the dominant process for angular momentum transfer for mass scales < 3 M sun for the strong magnetic field case. This critical mass scale can be understood semi-analytically as the time scale of magnetic braking. We show that the anisotropy of the angular momentum transfer due to the presence of strong magnetic field changes the resultant angular momentum of the core only by a factor of two. We also find that the distribution of the angle between the direction of the angular momentum and the magnetic field is random even just before the first core formation. Our results also indicate that the variety of the angular momentum of core inherited from the difference of the phase of the initial turbulent velocity field could contribute to the diversity in size and other properties of protoplanetary disks recently reported by observations.

Facilitator
-Name: Kanji Mori
Comment: English