カテゴリー: 科学研究部コロキウム

科学研究部コロキウム

2024.3.4-2024.3.10

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

2024.2.26-2024.3.3

February 28 Wed 10:30-12:00
Solar and Space Plasma Seminar
hybrid; Insei Seminar Room in Subaru Building and Zoom

February 28 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 28 Wed ===============

Campus： Mitaka
Seminar： Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic： Sporadic
Date and time：28 February (Wed), 10:30-12:00
Place： Insei Seminar Room and Zoom

Speaker：Dr. Yusuke Kawabata
Affiliation：The National Solar Observatory
Title：Multiline Stokes Synthesis of Ellerman Bombs: Obtaining Seamless Information from Photosphere to Chromosphere

Abstract：
There are many kinds of explosive phenomena caused by magnetic reconnections in the solar atmosphere. Ellerman bombs (EBs) are magnetic reconnection events occurring in weakly ionized and moderate plasma β (~1) environments in the solar photosphere and chromosphere. Owing to the observability of the physical quantities around the reconnection site, EBs are one of interesting observation targets for studying magnetic reconnections. While measuring the magnetic field in the solar corona is still difficult, inferring magnetic field in the chromosphere with high spatial resolution and reasonable temporal cadence will be achieved soon.

One such opportunity is SUNRISE III, which is an international balloon-borne solar observatory employing a 1 m diameter telescope. SUNRISE III will achieve five days of stable observations in a seeing-less environment at altitudes around 37 km. We are developing the Sunrise Chromospheric Infrared spectroPolarimeter (SCIP) as a focal plane instrument for SUNRISE III. SCIP will perform multi-line spectropolarimetric observations, enabling us to seamlessly diagnose the physical quantities (magnetic field, velocity field, and temperature) from the photosphere to the chromosphere.

In this talk, I would like to introduce the capability of SCIP for performing observations of magnetic reconnection events. In addition, I will present our recent study: we used a realistic magnetohydrodynamic (MHD) simulation of EB to study how SCIP will have access to the physical phenomena. We synthesized the polarimetric signals by solving radiative transfer equation based on the physical quantities in the MHD simulation and compared the polarimetric signals with the physical quantities in the MHD results. We found that the multiline observations of SCIP can detect the bidirectional flow associated with the EBs and suggest the height of the reconnection site.

Facilitator
-Name：Akiko Tei

Comment：English

=============== February 28 Wed===============

Campus: Mitaka
Seminar: NAOJ Science Colloquium
Date and time: 2023 Feb. 28 (Wed.), 15:30-16:30
Place: the lecture room / Zoom (hybrid)

Speaker: Kuria Watanabe
Affiliation: SOKENDAI (M2)
Title: The Chemical enrichment and origin of Nitrogen-Rich Galaxies at High Redshift
Abstract:
Chemical properties of young galaxies are important to understand the chemical evolution in galaxy formation. We investigate the origin of abundance ratios in JWST star-forming galaxies (z ~ 4-10) by comparing chemical evolution models.
The high N/O ratio in GN-z11, CEERS_01019, and GLASS_150008 observed with JWST cannot be explained by typical chemical evolution models including AGB stars. We focus on the three candidates of rich nitrogen, the Wolf-Rayet stars (WR), supermassive stars (SMS), and tidal disruption events (TDE). We develop the chemical evolution models of three candidates. Although the Ar/O values of the high N/O galaxies are not obtained, we find that the Ar/O values are the key to distinguishing between the three models. The three models can show the high N/O values as much as the N/O values in GN-z11, CEERS_01019, and GLASS_150008.
Because the time scale of high N/O is very short due to the CCSNe, the massive stars (>25 Msun) should directly collapse into black holes.

Speaker: Yuki Kambara
Affiliation: The University of Tokyo (M2)
Title: Planetesimal accretion in planetesimal rings
Abstract:
In the standard planet formation scenario, planetesimals have been assumed to be smoothly distributed in the radial direction except for the snowline. Recently, however, simulations of gas and dust evolution have shown that planetesimals form only in radially limited locations, such as gas pressure bumps and snowlines, and are concentrated in ring-like regions.
The evolution process of planetesimals distributed in a ring is crucial to understanding planet formation theory. However, the evolution of planetesimal rings has not been studied in detail. In this work, we investigate the evolution of planetesimal rings using N-body simulations. We systematically change the initial width and the total mass of planetesimal rings and investigate the dependence of protoplanet properties on the initial conditions. In all simulations, protoplanets undergo oligarchic growth while ring width expands due to scattering by protoplanets. In planetesimal rings, massive protoplanets tend to be formed around the ring center, while protoplanets far from the center of rings are less massive. Scaled orbital separation depends neither on the initial ring width nor the total mass and is consistent with the estimate in the oligarchic growth model. The width of the expanded planetesimal ring does not depend on the initial ring width but on the total ring mass. The maximum mass of protoplanets depends strongly on the total ring mass and weakly on the initial ring width.

Facilitator
-Name: Kazumasa Ohno

Comment: English

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