カテゴリー: 太陽系小天体セミナー

太陽系小天体セミナー

2024.2.19-2024.2.25

February 20 Tue 10:00-11:30
太陽系小天体セミナー
Zoom

February 20 Tue 16:00-17:00
NAOJ Seminar
hybrid; Lecture room and Zoom

February 21 Wed 14:30-15:30
ALMA-J seminar
hybrid; Room 102 in the ALMA building and Zoom

February 21 Wed 15:30-16:30
NAOJ Science Colloquium
hybrid; Lecture room and Zoom

詳細は下記からご覧ください。

=============== February 20 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：2月20日（火曜日）10時00分～11時30分
場所：zoom
講演者：小林美樹
タイトル：はやぶさ・はやぶさ2光度比較
Abstract：はやぶさ2サンプルリターンカプセルは、当初予想されていた最大光度約－４等級よりも暗い結果となったことを、はやぶさ初号機と比較考慮する。

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

=============== February 20 Tue===============

Campus：Mitaka
Seminar：NAOJ Seminar
Regularly Scheduled/Sporadic：Sporadic
Date and time：February 20, 2024 16:00-17:00
Place：Zoom/Lecture Room (hybrid)

Speaker：Dr. Nicolas Peretto

Affiliation：Cardiff University

Title：On the formation of star clusters in self-gravitating molecular clouds

Abstract:The formation of stellar clusters dictates the pace at which galaxies evolve, and solving the question of their formation will undoubtedly lead to a better understanding of the Universe as a whole. While it is well known that star clusters form within parsec-scale over-densities of interstellar molecular gas called clumps, it is, however, unclear whether these clumps represent the high-density tip of a continuous gaseous flow that gradually leads towards the formation of stars, or a transition within the gas physical properties. Here, I will present a unique analysis of a sample of 27 infrared dark clouds embedded within 24 individual molecular clouds that combine a large set of observations, allowing us to compute the mass and velocity dispersion profiles of each, from the scale of tens of parsecs down to the scale of tenths of a parsec. These profiles reveal that the vast majority of the clouds, if not all, are consistent with being self-gravitating on all scales, and that the clumps, on parsec-scale, are often dynamically decoupled from their surrounding molecular clouds, exhibiting steeper density profiles (ρ∝r-2) and flat velocity dispersion profiles (σ∝r0), clearly departing from Larson’s relations. These findings suggest that the formation of star clusters correspond to a transition regime within the properties of the self-gravitating molecular gas. We propose that this transition regime is one that corresponds to the gravitational collapse of parsec-scale clumps within otherwise stable molecular clouds. I will also present two follow-up studies at high angular resolution that provide direct constraints on how clump collapse proceeds.

Facilitator
-Name：Takashi Moriya

=============== February 21 Wed===============

Campus: Mitaka
Seminar: ALMA-J seminar
Date and time: February 21 (Wed) 14:30-15:30
Place: hybrid (room 102 in the ALMA building and Zoom)

Speaker: Yuhua Liu
Affiliation: Department of Earth and Planetary Sciences, Faculty of Sciences, Kyushu University
Title: Dust Polarization of Prestellar and Protostellar Sources in OMC-3

Abstract:
We present the Atacama Large Millimeter/submillimeter Array (ALMA) observations of linearly polarized 1.1 mm continuum emission at ~0.14” (55 au) resolution and CO (J=2-1) emission at ~1.5” (590 au) resolution towards one prestellar (MMS 4), four Class 0 (MMS 1, MMS 3, MMS 5, and MMS 6), one Class I (MMS 7), and one flat-spectrum (MMS 2) sources in the Orion Molecular Cloud 3 region. The dust disk-like structures and clear CO outflows are detected towards all sources except for MMS 4. The diameters of these disk-like structures, ranging from 16 to 97 au, are estimated based on the deconvolved full width half maximum (FWHM) values obtained from the multi-Gaussian fitting. Polarized emissions are detected towards MMS 2, MMS 5, MMS 6, and MMS 7, while no polarized emission is detected towards MMS 1, MMS 3, and MMS 4. MMS 2, MMS 5, and MMS 7 show organized polarization vectors aligned with the minor axes of the disk-like structures, with mean polarization fractions ranging from 0.6% to 1.2%. The strongest millimeter source, MMS 6, exhibits complex polarization orientations and a remarkably high polarization fraction of ~10% around the Stokes I peak, and 15%-20% on the arm-like structure, as reported by Takahashi et al. (2019). The origins of the polarized emission, such as self-scattering and dust alignment due to the magnetic field or radiative torque, are discussed for individual sources. Some disk-like sources exhibit a polarized intensity peak shift towards the nearside of the disk, which supports that the polarized emission originates from self-scattering.

=============== February 21 Wed==============

Campus: Mitaka
Seminar: NAOJ Science Colloquium
Date and time: 2023 Feb. 21 (Wed.), 15:30-16:30
Place: the lecture room / Zoom (hybrid)

Speaker: Tatsuya Matsumoto
Affiliation: Kyoto University
Title: Effects of internal heating sources on hydrogen-rich supernova light curves
Abstract:
Core-collapse supernovae (SNe) are caused by the death of massive stars, and their light curves provide a lot of information about the stellar evolution and physical processes of explosions. In particular, the light curves of hydrogen-rich SNe have a characteristic slowly-evolving phase, so-called the plateau phase, whose luminosity and duration are related to the SN parameters such as ejecta mass and energy. Recent observations revealed that some H-rich SNe exhibit evidence for a sustained energy source powering their light curves, resulting in a brighter and/or longer-lasting plateau phase.

We present a semi-analytic light curve model that accounts for the effects of an arbitrary internal heating source such as 56Ni/Co decay, a central engine (millisecond magnetar or accreting compact object), and shock interaction with a dense circumstellar disk.

While a sustained internal power source can boost the plateau luminosity commensurate with the magnitude of the power, the duration of the recombination plateau can typically be increased by at most a factor
∼2−3 compared to the zero-heating case. For a given ejecta mass and initial kinetic energy, the longest plateau duration is achieved for a constant heating rate at the highest magnitude that does not appreciably accelerate the ejecta. This finding has implications for the minimum ejecta mass required to explain particularly long-lasting supernovae, and for confidently identifying rare explosions of the most-massive hydrogen-rich (e.g. population III) stars.

Facilitator
-Name: Koh Takahashi

Comment: English

2024.2.12-2024.2.18

February 13 Tue 10:00-11:30
太陽系小天体セミナー
Zoom

February 13 Tue 11:00-12:00
SOKENDAI Doctoral Thesis Preliminary Evaluation
hybrid; Large Seminar Room in Subaru Building and Zoom

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

February 14 Wed 15:30-16:30
NAOJ Science Colloquium
hybrid; Lecture room and Zoom

February 16 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。

=============== February 13 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：2月13日（火曜日）10時00分～11時30分
場所：zoom
講演者：有松 亘
タイトル：中・大型太陽系外縁天体による恒星掩蔽キャンペーン観測の現状
Abstract：既知の太陽系外縁天体による恒星掩蔽イベントの観測は、外縁天体のサイズ・形状の決定、および衛星や環、表面大気への制約を得るうえで極めて有用である。本発表では現在国内の複数の観測装置を用いて実施している外縁天体恒星掩蔽キャンペーン観測の現状を報告する。

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

=============== February 13 Tue ===============

Campus：Mitaka
Seminar：SOKENDAI Doctoral Thesis Preliminary Evaluation
　　　　 総研大博士学位論文予備審査会
Regularly Scheduled/Sporadic：Sporadic
Date and time：February 13, 2024　11:00～12:00

Place : Large Seminar Room and Zoom

Speaker：Yuta Tashima
Title：Elucidation of galactic magnetic field structure by pseudo-observation focusing on depolarization

Facilitator
-Name：Nozomu Tominaga, Hideyuki Kobayashi, Natsuko Fujii (Graduate Student Affairs Unit)

=============== February 14 Wed===============

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

Speaker: Yulong GAO
Affiliation: School of Astronomy and Space Science, Nanjing University, Nanjing, China
Title: Unraveling the Low-Metallicity Merging Dwarf Galaxies: Insights into Starburst and Metal Dilution/Enrichment

Abstract:
Understanding the physical mechanisms driving starbursts within dwarf galaxies remains a challenge in astrophysics. Moreover, the impact of mergers on star formation activity in these galaxies remains unclear. In this talk, we employ observations from the VLT/MUSE and ALMA to investigate how the merger process influences star formation activities in metal-poor dwarf galaxies, focusing on galaxies of Haro 11 and NGC 4809/4810. Haro 11, situated in the late-stage merger phase, exhibits similar morphology and kinematics to the Antennae galaxy, offering valuable insights into the merger-induced starburst phenomenon. Conversely, the ongoing collision between NGC 4809 and NGC 4810 presents a unique opportunity to examine the effects of mergers on dwarf galaxies in real time, particularly within their overlapping regions. We find post-merger between low mass galaxies (e.g., Haro 11) can trigger global starburst, similar to ULIRGs. Notably, Haro 11 could be the analog of high-z dwarf starbursts and the potential progenitor of the nearby less massive elliptical galaxies. Furthermore, we find that NGC 4809/4810 interaction zone show enhanced SFR (sSFR), and deficient metallicity, indicating the capacity of dwarf galaxy mergers to instigate significant star formation activity even within metal-poor environments. Additionally, we detect clear evidence of metal enrichment resulting from the Type Ic SN 2011jm within NGC 4809, representing a pioneering detection of chemical pollution through stellar feedback beyond the Local Volume. These findings shed light on the underlying mechanisms driving starburst and stellar feedback processes within the dwarf galaxies.

=============== February 14 Wed==============

Campus: Mitaka
Seminar: NAOJ Science Colloquium
Date and time: 2023 Feb. 14 (Wed.), 15:30-16:30
Place: the lecture room / Zoom (hybrid)

Speaker: Ryota Kitamura
Affiliation: The University of Tokyo (M1)
Title: Review on Pan et al. (2022) “The terrestrial planet formation around M dwarfs: in situ, inward migration, or reversed migration”
Abstract of the paper:
Terrestrial planets are commonly observed to orbit M dwarfs with close-in trajectories. In this work, we extensively perform N-body simulations of planetesimal accretion with three models of in situ, inward migration, and reversed migration to explore terrestrial formation in tightly compact systems of M dwarfs. In the simulations, the solid discs are assumed to be 0.01 per cent of the masses of host stars and spread from 0.01 to 0.5 au with the surface density profile scaling with r−k according to the observations. Our results show that the in-situ scenario may produce 7.77+3.23 −3.77 terrestrial planets with an average mass of 1.23+4.01 −0.93 M⊕ around M dwarfs. The number of planets tends to increase as the disc slope is steeper or with a larger stellar mass. Moreover, we show that 2.55+1.45 −1.55 planets with a mass of 3.76+8.77 −3.46 M⊕ are formed in the systems via inward migration, while 2.85+1.15 −0.85 planets with 3.01+13.77 −2.71 M⊕ are yielded under reversed migration. Migration scenarios can also deliver plentiful water from the exterior of the ice line to the interior due to more efficient accretion. The simulation outcomes of the reversed migration model produce the best match with observations, being suggestive of a likely mechanism for planetary formation around M dwarfs

Speaker: Miho Tan
Affiliation: SOKENDAI (M1)
Title: Effect of stellar wind on SS433’s jet propagation
Abstract:
SS433 is an X-ray binary system consisting of a star and a compact star, and the compact star is known to emit spiral binaries. The jets propagate more than 100 pc; in Ohmura et al (2021) and other groups, uniform jets injected from 1 pc propagated 100 pc. But one of the important questions is how to travel to 1pc from the ejection region.
Therefore, in this study, we evaluate the propagation of the jet within 1pc including the effect of stellar winds. Since the orbital period of the binary is shorter than the jet propagation timescale, we assume the propagation area becomes turbulence formed by the stellar wind. We put turbulent velocity fields of 0.1% and 0.01% of the jet velocity in the ambient around the jet to see the effect of the turbulence on the jet propagation.

Facilitator
-Name: Doris Arzoumanian

Comment: English

=============== February 16 Fri==============

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

Speaker：Prof. Hideyuki Kobayashi
Affiliation：National Astronomical Observatory of Japan (NAOJ)
Title：Japanese VLBI development and research that I have been involved in

Abstract: Japanese VLBI development and research that I have been involved in, are reviewed. The VSOP programme, the world’s first space VLBI observation with the HALCA satellite launched in 1997, VERA which is specialized in astrometry and began construction in 2000, as well as the organisation of the East Asian VLBI observation network with the development of the domestic VLBI network are described. Expectations for the next generation of radio telescopes, the SKA, are also discussed.

Facilitator
-Name：Takashi Moriya

2024.2.5-2024.2.11

February 6 Tue 10:00-11:30
太陽系小天体セミナー
Zoom

February 7 Wed 14:00-15:00
ALMA-J seminar
hybrid; Small seminar room in the Subaru building and Zoom

February 7 Wed 15:30-16:30
NAOJ Science Colloquium
hybrid; Large Seminar Room in Subaru Building and Zoom

February 9 Fri 10:30-12:00
Solar and Space Plasma Seminar
Zoom

February 9 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。

=============== February 6 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：2月6日（火曜日）10時00分～11時30分
場所：zoom
講演者：和田 空大
所属：東京大学
タイトル：Tomo-e Gozen NEO 探査改善プロジェクトの現状共有と今後の展望
Abstract：東京大学木曽観測所では2019年から地球接近小惑星 (NEOs)
の探査を開始し、現在までで多数の小惑星の発見や物理量の測定を行ってきました。
探査を行うにつれ現在のプロセスの課題が浮き彫りになっており、私が主導して改善を試みている最中です。
今回の発表では、プロセス全体の中でも特に移動天体検出に使っている機械学習モデルについて、その改善の方針と現状共有をします。

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

=============== February 7 Wed ===============

Campus: Mitaka
Seminar: ALMA-J seminar
Date and time: February 7 (Wed) 14:00-15:00
Place: hybrid (Small seminar room in the Subaru building and Zoom)

Speaker: Yuhito Shibaike
Affiliation: NAOJ
Title: Constrains on the properties of forming planets from the dust continuum emission of the circumplanetary disks

Abstract:
Although there have been a lot of theoretical research on the formation of gas planets, observational supports have still been very rare. The young T Tauri star PDS 70 has two gas accreting planets sharing one large gap in a pre-transitional disk, which is a valuable system to obtain observational constraints. Recently, dust continuum emission from PDS 70 c has been detected by ALMA Band 7, considered as the evidence of a circumplanetary disk (CPD), a small gas (and dust) disk formed around the planet as a byproduct of the gas accretion. To obtain constraints on the planet properties, we introduce a model of dust evolution in the CPD and reproduce the detection of the dust continuum emission. We find positive correlations between the intensity of the dust emission and three important planet properties, the planet mass, gas accretion rate, and their product called MMdot. We then find that the MMdot of PDS 70 c must be larger than 0.4 MJ^2 /yr, corresponding to the lower limits of the planet mass and the gas accretion rate, 5 MJ and 0.02 MJ/yr. This is the first case to succeed in obtaining constraints on planet properties from the dust continuum emission of a CPD. We also find some loose constraints on the properties of PDS 70 b from the non-detection of its dust emission. We propose possible scenarios for the PDS 70 b and c explaining the non-detection respectively detection of the dust emission from their CPDs. I will also discuss my future plans to obtain constraints on other gas accreting planets if there is enough time.

=============== February 7 Wed===============

Campus: Mitaka
Seminar: NAOJ Science Colloquium
Date and time: 2023 Feb. 7 (Wed.), 15:30-16:30
Place: the large seminar room / Zoom (hybrid)

Speaker: Yui Kawashima
Affiliation: ISAS/JAXA
Title: Subaru/IRD high-resolution spectroscopy of a T-type brown dwarf and investigation of its atmospheric properties with high-resolution spectrum model ExoJAX
Abstract:
While brown dwarf atmospheres share composition and temperature with those of extrasolar gas giant planets, in general, brown dwarfs are observable with a higher signal-to-noise ratio when compared to exoplanets. Thus, the observation of brown dwarf atmospheres helps us establish our understanding of various processes in the atmospheres of such temperature and composition, including chemistry, thermal structure, dynamics, and cloud formation. Also, their high-resolution spectra serve as excellent templates for the observational validation of the molecular line lists at such high temperatures. The accuracy of molecular line lists holds the key to detecting chemical species in exoplanet atmospheres, which are often observed with a lower signal-to-noise ratio.

Recently, we observed the high-resolution spectrum of a T6.5-type brown dwarf Gl 229B with the InfraRed Doppler (IRD) spectrograph mounted on the Subaru Telescope. We have constrained its atmospheric properties, such as the molecular abundances and thermal structure, using an inverse-problem approach with our high-resolution spectrum model ExoJAX (Kawahara, Kawashima et al. 2022). We have also investigated the possibility of inferring the object mass using the embedded information on collision-induced absorption uniquely accessible by high-resolution spectroscopy. Furthermore, we have revealed that in some wavelength regions, specific molecular line lists do not match the observed absorption features.

Facilitator
-Name: Kazumasa Ohno

Comment: English

=============== February 9 Fri==============

Campus： Mitaka
Seminar： Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic： Sporadic
Date and time：9 February (Fri), 10:30-12:00
Place： Zoom

Speaker：Dr. Tetsu Anan
Affiliation：The National Solar Observatory
Title：Measurements of a reconnection electric field in the solar chromosphere

Abstract：The efficient release of magnetic energy in astrophysical plasmas can be achieved through magnetic-field diffusion, the rate of which is directly tied to the associated electric field. However, there have been only a
few attempts to measure electric fields in the solar atmosphere, because of the common assumption that electric fields must vanish quickly or only exist at unresolvable spatial scales. Using the newly commissioned National Science Foundation’s Daniel K. Inouye Solar Telescope (DKIST), we observed NOAA active region 12995 on February 23rd, 2022, in three spectral bands 397 nm, 630 nm, and 854 nm using the Visible SpectroPolarimeter (ViSP). We successfully obtained Stokes spectra of an Ellerman bomb, which is brightening in the lower chromosphere and are thought to be associated with magnetic reconnection. At the Ellerman bomb, we discovered a broadband circular polarization in a Balmer line of the neutral hydrogen at 397 nm, H epsilon, that can only be explained by the presence of an electric field. Moreover, we found that the measured signal filled a region up to ~1000 km, which is three orders of
magnitude larger than that expected in theory. In this talk, we will present our findings and discuss why the diffusion region is so large, and what is the next step.

Facilitator
-Name：Akiko Tei

Comment：English

=============== February 9 Fri==============

Campus：Mitaka
Seminar：NAOJ Seminar
Regularly Scheduled/Sporadic：Regular
Date and time：February 9, 2024 16:00-17:00
Place：Zoom/Large Seminar Room (hybrid)

Speaker：Dr. Eleonora Di Valentino
Affiliation：University of Sheffield

Title：Unresolved Anomalies and Tensions in the Standard Cosmological Model

Abstract: The standard Lambda Cold Dark Matter cosmological model has been incredibly successful in explaining a wide range of observational data, from the cosmic microwave background radiation to the large-scale structure of the universe. However, recent observations have revealed a number of inconsistencies among the model’s key cosmological parameters, which have different levels of statistical significance. These include discrepancies in measurements of the Hubble constant, the S8 tension, and the CMB tension. While some of these inconsistencies could be due to systematic errors, the persistence of such tensions across various probes suggests a potential failure of the canonical LCDM model. I will examine these inconsistencies and discuss possible explanations, including modifications to the standard model, that could potentially alleviate them. However, I will also discuss the limitations of these proposed solutions and note that none of them have successfully resolved the discrepancies.

Facilitator
-Name：Takashi Moriya

2024.1.29-2024.2.4

January 30 Tue 10:00-16:40
SOKENDAI Progress Report Defense in the second semester, AY2023
2023年度後期　総研大研究中間レポート発表会
hybrid; 中央棟(北)1階　講義室およびZoom

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

January 31 Wed 10:00-12:00
SOKENDAI Doctoral Thesis Dissertation review
総研大博士学位論文予備審査会
hybrid; Lecture Room and Zoom

January 31 Wed 10:30-12:00
SOKENDAI Colloquium
hybrid; Large Seminar Room in Subaru Building and Zoom

January 31 Wed 15:30-16:30
NAOJ Science Colloquium
hybrid; the 3F seminar room in Instrument Development Building No.3 and Zoom

February 1 Thu 14:00-15:00
Tea Talk
Zoom

詳細は下記からご覧ください。

=============== January 30 Tue ===============

キャンパス：三鷹
セミナー名：2023年度後期　総研大研究中間レポート発表会
(SOKENDAI Progress Report Defense in the second semester, AY2023)
定例・臨時の別：臨時
日時：2023年1月30日（火）　10:00～16:40
場所：中央棟(北)1階　講義室およびZoom

講演者：柿元　拓実（10:00～）(Takumi Kakimoto)
所属：総研大　天文科学専攻 (the Department of Astronomical Science, SOKENDAI)
タイトル：The formation history of a massive quiescent galaxy in a group environment at z = 4.53

講演者：中野　すずか（10:50～）(Suzuka Nakano)
所属：総研大　天文科学専攻 (the Department of Astronomical Science, SOKENDAI)
タイトル：塵に埋もれた活動的な超巨大ブラックホールの発掘を可能とするサブミリ波帯熱源診断法の開発

講演者：渡辺　くりあ（13:00～)（Kuria Watanabe）
所属：総研大　天文科学専攻 (the Department of Astronomical Science, SOKENDAI)
タイトル：Uncovering the Physical Origin of Elemental Abundances in Early Galaxies Formation through Observations and Modeling

講演者：波多野　駿（13:50～）（Shun Hatano）
所属：総研大　天文科学専攻 (the Department of Astronomical Science, SOKENDAI)
タイトル：Exploring for Intermediate Mass Black Holes with Optical Spectra and Near-infrared Luminosity Variability Data.

講演者：内藤　由浩（15:00～）（Yoshihiro Naito）
所属：総研大　天文科学専攻 (the Department of Astronomical Science, SOKENDAI)
タイトル：Spectroscopic study of Alfvén waves in coronal holes as an energy source for the fast solar wind acceleration

講演者：佐藤　慶暉（15:50～）（Yoshiaki Sato）
所属：総研大　天文科学専攻 (the Department of Astronomical Science, SOKENDAI)
タイトル：Study of Electron Acceleration in Solar Flares with X-ray Focusing-Imaging　Spectroscopy and Test-Particle Simulation

世話人の連絡先
-名前：大学院係　松田

=============== January 30 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：1月30日（火曜日）10時00分～11時30分
場所：zoom
講演者：紅山仁
所属：東京大学
タイトル：地球接近小惑星の観測計画2024
Abstract：発表者が2024年に実施する二件の地球接近小惑星の観測計画について発表します。多くの方々のコメントを歓迎いたします。

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

=============== January 31 Wed===============

Campus：Mitaka
Seminar：SOKENDAI Doctoral Thesis Dissertation review 総研大博士学位論文予備審査会
Regularly Scheduled/Sporadic：Sporadic
Date and time：January 31, 2024 10:00-12:00
Place ：Lecture Room and Zoom

Speaker：Yui Kasagi
Title：Unveiling Atmospheric Features of Faint Substellar Companions from High-Resolution Near-Infrared Spectra

Facilitator
-Name：Nozomu Tominaga, Hideyuki Kobayashi, Kaya Kitabayashi (Graduate Student Affairs Unit)

Comment:
https://guas-astronomy.jp/CampusLife/doctor_report.html

=============== January 31 Wed==============

Campus：Mitaka
Seminar：SOKENDAI Colloquium
Regularly Scheduled/Sporadic：Regular
Date and time：January 31, 2024 10:30-12:00
Place：Large Seminar Room in Subaru Building and Zoom

Speaker: Shubham Bhardwaj
Affiliation: SOKENDAI 4th year (D2) (Supervisor: Maria Dainotti, Nozomu Tominaga, Kazunari Iwasaki)
Title: GRB Redshift Estimation Using Machine Learning

Facilitator
-Name：Matsuda, Graduate Student Affairs Unit

=============== January 31 Wed==============

Campus: Mitaka
Seminar: NAOJ Science Colloquium
Date and time: 2023 Jan. 31 (Wed.), 15:30-16:30
Place: the 3F seminar room in Instrument Development Building No.3 / Zoom (hybrid)

Speaker: Shun Hatano
Affiliation: NAOJ (M2)
Title: Origin of high-ionization lines found in extremely metal poor galaxies.
Abstract:
The extreme metal poor galaxies (EMPG) exhibit intense high-ionization emission lines, such as He II4686, unexplained by stellar synthesis models. Umeda et al. (2022) employed CLOUDY and MCMC to reproduce the observed spectrum, revealing an unidentified non-thermal radiation source. In this study, we introduce [Ne V]3426 emission (97.1 eV) and estimate spectral indices and luminosities for EMPGs in the 54.4-97.1 eV range. Confirming that non-thermal radiation dominates the 54.4-97.1 eV range for all the galaxies with [Ne V]3426 detections, we discuss the origin of the non-thermal radiation.

Speaker: Ryota Hatami
Affiliation: NAOJ (M1)
Title: Synthesis of Sc, Ti, and V in core-collapse supernovae
Abstract:
A supernova explosion is an explosive phenomenon that occurs at the end of the life of a massive star. However, the explosion mechanism has not yet been clarified. As a clue to investigate the explosion mechanism, we focused on nucleosynthesis. Metal-poor stars reflect the result of explosive nucleosynthesis in supernova explosions of first stars, and reproducing the chemical abundances of metal-poor stars is one of the important issues in the nucleosynthetic calculation. Recently correlations among Sc, Ti, and V are observationally identified.
Nevertheless, the abundances of Sc, Ti, and V in metal-poor stars have not been reproduced by nucleosynthesis calculations based on the results of hydrodynamical simulation. This is because one of the possible causes is that the explosion mechanism is not yet understood. Then, we attempted to constrain the explosion mechanism by (1) performing nucleosynthesis calculations with setting temperature, density, neutrino flux, etc. as parameters to find physical conditions which reproduce the observed chemical composition of metal-poor stars, and (2) examining the feasibility of these conditions by comparing them with 2D explosion simulations. In this talk, the progress of (1) and (2) will be discussed.

Facilitator
-Name: Masamitsu Mori

Comment: English

=============== February 1 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：2/1（木）14：00～15：00
場所：Zoom
講演者：平松　正顕
所属：天文情報センター周波数資源保護室
タイトル：世界無線通信会議とドバイ4週間の旅
言語：日本語（PPTは英語も併記）

世話人の連絡先：
-名前：藤田登起子

備考：
参加方法：Zoom

2024.1.22-2024.1.28

January 23 Tue 10:00-11:30 太陽系小天体セミナー
Zoom

January 24 Wed 10:30-12:00 SOKENDAI Colloquium
Large Seminar Room in Subaru Building and Zoom (hybrid)

January 24 Wed 13:00-15:00 SOKENDAI Doctoral Thesis Dissertation review
Lecture Room and Zoom (hybrid)

January 24 Wed 13:30-15:00 Solar and Space Plasma Seminar
Insei Seminar Room and Zoom(hybrid)

January 24 Wed 14:30-15:30 ALMA-J seminar
Room 102 in the ALMA Building and Zoom (hybrid)

January 24 Wed 15:30-16:30 NAOJ Science Colloquium
the 3F seminar room in Instrument Development Building No.3 and Zoom (hybrid)

詳細は下記からご覧ください。

=============== January 23 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：1月23日（火曜日）10時00分～11時30分
場所：zoom
講演者：匠あさみ

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

=============== January 24 Wed ===============

Campus：Mitaka
Seminar：SOKENDAI Colloquium
Regularly Scheduled/Sporadic：Regular
Date and time：January 24, 2024 10:30-12:00
Place：Large Seminar Room in Subaru Building and Zoom

Speaker: Takumi Kakimoto
Affiliation: SOKENDAI 2nd year (M2) (Supervisor: Masayuki Tanaka, Daisuke Iono, Kiyoto Yabe)
Title: Star formation activity in a massive protocluster at z=4.5

Speaker: Chanoul Seo
Affiliation: SOKENDAI 5th year (D3) (Supervisor: Yuka Fujii, Masahiro Ikoma, Hideko Nomura)
Title: Impact of Magma Redox States on Super-Earth Atmospheres:Unveiling the Connection with Atmospheric Composition

Facilitator
-Name：Matsuda, Graduate Student Affairs Unit

=============== January 24 Wed===============

Campus：Mitaka
Seminar：SOKENDAI Doctoral Thesis Dissertation review
　　　　総研大博士学位論文予備審査会
Regularly Scheduled/Sporadic：Sporadic
Date and time：January 24, 2024 13:00-15:00
Place ：Lecture Room and Zoom

Speaker：Takaho Masai
Title：A Study on the Design of Receiver Optics and Waveguide Components Towards High-Performance (Sub)millimeter Wave Multibeam Receivers

Facilitator
-Name：Nozomu Tominaga, Hideyuki Kobayashi, Kaya Kitabayashi (Graduate Student Affairs Unit)

Comment:
https://guas-astronomy.jp/CampusLife/doctor_report.html

=============== January 24 Wed==============

Campus： Mitaka
Seminar： Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic： Sporadic
Date and time：24 January (Wed), 13:30-15:00
Place： hybrid; Insei Seminar Room and Zoom

Speaker：Dr. Yoichiro Hanaoka
Affiliation：NAOJ
Title：Observation of the White-Light Corona at Total Solar Eclipses (Focusing
on Polarization Measurements)
Abstract：Total solar eclipses are good chances to observe the inner white-light corona under a very low background level. Combining the eclipse data and those from spaceborne coronagraphs such as SOHO/LASCO, we can obtain the distribution of the coronal material regardless of the temperature from just above the limb to tens of solar radii.
For this purpose, we carried out eclipse observations several times with amateur observers using polarimetry instruments. Polarimetry is indispensable to separate the K-corona (million-kelvin plasma) from the F-corona (interplanetary dust), and therefore, all the spaceborne coronagraphs have polarimetric capacity.
The results from the eclipses unexpectedly show a systematic difference between the polarimetry results obtained during the eclipses and those by LASCO. The degree of polarization obtained by LASCO is about 30 % less than the eclipse results and it was revealed that combining the eclipse and LASCO data is difficult. This result suggests that the polarimetric calibration of LASCO should be re-examined.
Some future space missions carrying white-light coronagraphs are planned, and they may also have difficulty in polarimetric calibrations. Repeated eclipse observations are expected to provide good calibration data for space coronagraphs. After a consistent calibration becomes possible, the precise distribution of coronal material in the wide range will be obtained.

Facilitator
-Name：Akiko Tei

Comment：English

=============== January 24 Wed==============

Campus: Mitaka
Seminar: ALMA-J seminar
Date and time: January 24 (Wed) 14:30-15:30
Place: hybrid (Room 102 in the ALMA building and Zoom)

Speaker: Kianhong Lee
Affiliation: Tohoku University
Title: ALMA [CII] observations of TN J0924-2201, the radio galaxy at z~5.2

Abstract:
High-redshift radio galaxies are massive star-forming galaxies with powerful radio jets, often located on or below the star-forming main sequence of galaxies, indicating that they are in the process of being quenched. TN J0924-2201 is one of the most distant known radio galaxies, associated with three CO(1-0)-detected companions at z~5.2. In this talk we will present ALMA observations of [CII] 158 um line and the corresponding 1-mm continuum emission of TN J0924-2201. While obtaining the [CII] line and 1mm continuum emission at the host galaxy, our observations revealed no detection at the positions of the three CO(1-0) companions. The derived systematic redshift z_[CII] of the host galaxy from the [CII] is ~5.17, indicating a velocity offset of ~1200 km/s with respect to z_Lya, marking the largest velocity offset between [CII] and Lya recorded at z > 5 to date. Within the host galaxy, we identified an extended [CII] structure with a velocity of ~700 km/s, suggestive of an outflow. This finding aligns with the shell outflow model, providing consistency with the observed large velocity offset of Lya. Assuming three massive CO(1-0) companions are also outflows, their velocities of ~1500 km/s surpass the escape velocity of a 10^13 Msun halo, implying the removal of molecular gas from the system of TN J0924-2201. Our observations and results revealed that we are witnessing a distinctive phase of radio galaxies in their evolution.

=============== January 24 Wed==============

Campus: Mitaka
Seminar: NAOJ Science Colloquium
Date and time: 2023 Jan. 24 (Wed.), 15:30-16:30
Place: the 3F seminar room in Instrument Development Building No.3 / Zoom (hybrid)

Speaker: Ryota Ichimura
Affiliation: NAOJ (D1)
Title: Carbon Isotope Fractionation of Complex Organic Molecules in Star-Forming Cores
Abstract:
Recent high-resolution and sensitivity ALMA observations have unveiled the carbon isotope ratios (12C/13C) of Complex Organic Molecules (COMs) in a low-mass protostellar source. To understand the 12C/13C ratios of COMs, we investigated the carbon isotopic fractionation of COMs from prestellar cores to protostellar cores with a gas-grain chemical network model. We confirmed that in the prestellar phase, the 12C/13C ratios of small molecules are bimodal: CO and species formed from CO (e.g.,CH3OH) are slightly enriched in 13C compared to the local ISM (by ∼ 10 %), while those from C and C+ are depleted in 13C owing to isotope exchange reactions. COMs are formed from the simple species on grain surface, and thus basically inherit the bimodality of 12C/13C. In the protostellar phase, COMs are formed on the grain surface and in the hot gas (> 100 K) and have different 12C/13C from those in the prestellar phase. We additionally incorporate reactions between gaseous atomic C and H2O ice or CO ice on the grain surface to form H2CO ice or C2O ice suggested by recent laboratory studies. The direct C-atom addition reactions open pathways to form 13C-enriched COMs from atomic C and CO ice. We find that these direct C-atom addition reactions mitigate isotope fractionation, and the model with the direct C-atom addition reactions better reproduces the observations than our base model. Our calculations also show that cosmic-ray ionization rates affect the 12C/13C ratios of COMs.

Speaker: Akifumi Matsumura
Affiliation: The University of Tokyo (M1)
Title: Estimating the characteristics of ejecta from magma ocean for water production on the protoplanet
Abstract:
How water is delivered to rocky planets during the planet-forming stage is a major issue in planetary science. While many previous studies considered water delivery by icy planetesimals, we consider water production by chemical interaction between the primordial atmosphere and the surface of the magma ocean of a rocky planet growing through planetesimal accretion. Previous studies based on this idea assumed that iron oxides in the magma ocean and atmospheric hydrogen are always in constant contact, which must be examined; namely, we need to consider properly how to bring the magma into contact with the atmosphere. In this study, we focus on the reaction between the atmospheric gas and the materials ejected from the magma ocean when planetesimals collide with the magma ocean surface during the growth phase of a planet. I am currently studying the scatter of magma upon the impact of planetesimals on the planet’s surface and its influence on the atmospheric composition. In this talk, I will describe our progress in the research to date and future research plans.

Facilitator
-Name: Kanji Mori

Comment: English