ALMA Jセミナー – ページ 3 – 国立天文台　セミナー情報　/　Seminar Information

2024.5.13-2024.5.19

May 14 Tue 10:00-11:30
太陽系小天体セミナー (Solar System Minor Body Seminar)
Zoom

May 14 Tue 13:00-13:40
SOKENDAI Doctoral Thesis Preliminary Evaluation
総研大博士学位論文予備審査会
hybrid; Large Seminar Room in Subaru Building and Zoom

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

May 15 Wed 14:30-15:30
ALMA-J seminar
hybrid; Large Seminar Room in Subaru Building and Zoom

詳細は下記からご覧ください。

=============== May 14 Tue===============

キャンパス：三鷹
セミナー名：太陽系小天体セミナー (Solar System Minor Body Seminar)
定例・臨時の別：定例
日時：　5月　14日（火曜日）10時00分～11時30分
場所：zoom
講演者：佐藤幹哉
所属: 国立天文台　

世話人の連絡先
-名前：渡部潤一
備考：zoomでの参加

=============== May 14 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: May 14, 2024　13:00-13:40
Place: Large Seminar Room and Zoom

Speaker: Kiyoaki Doi
Title: Constraining Physical Properties of Protoplanetary Disks from Spatial Distributions of Dust Millimeter Continuum Observations

Facilitator
-Name: Ken’ichi Tatematsu, Tomoya Hirota, Kazunari Iwasaki

(Graduate Student Affairs Unit)

===============May 15 Wed==============

Campus：Mitaka
Seminar：SOKENDAI Colloquium
Regularly Scheduled/Sporadic：Scheduled
Date and time：May 15, 2024 10:30-12:00
Place：Large Seminar Room in Subaru Building and Zoom

Speaker：Abdurrahman Naufal
Affiliation：SOKENDAI 4th year (D2) (Supervisor: Yusei Koyama, Masayuki Tanaka, Yuichi Matsuda)
Title：Deep census of the Spiderweb protocluster members with HST slitless spectroscopy observation

Facilitator
-Name：Yoshiaki Sato
Comment：Language: English

===============May 15 Wed==============

Campus: Mitaka
Seminar: ALMA-J seminar
Date and time: 2024 May. 15 (Wed.), 14:30-15:30 JST
Place: Subaru building, Large seminar room / Zoom (hybrid)

Speaker: Kshitiz Mallick
Affiliation: NAOJ
Title: Observational study of high-mass star formation at the junction of filaments
Abstract:
Understanding high-mass star formation is an important pillar of astronomical research, due to the large impact of such sources on their natal environment.
Various paradigms have been proposed for the formation of such stellar sources, with hub filament systems (HFS) having emerged as an important contender for understanding not only how massive stars form, but also the evolution of a molecular cloud as it collapses and fragments to form stars. In this talk, I present the results of my recent observational analysis of some high-mass star forming regions, carried out using molecular data cubes, complemented by other multiwavelength data. We discuss the complex nature of such star forming regions, the conundrums faced in analysis of hubs and filamentary structures, and the further work one needs to undertake to fully comprehend the connection between(high-mass) star formation and HFS.

Facilitator
-Name: Yu Cheng

2024.4.15-2024.4.21

April 16 Tue 10:00-11:30
太陽系小天体セミナー (Solar System Minor Body Seminar)
Zoom

April 17 Wed 14:30-15:30
ALMA-J seminar
hybrid; Room102 in ALMA Building and Zoom

April 17 Wed 15:30-16:30
NAOJ Science Colloquium
hybrid; Large Seminar Room in Subaru Building and Zoom

April 18 Thu 15:00-16:30
Solar and Space Plasma Seminar
hybrid; Insei Seminar Room in Subaru Building and Zoom

詳細は下記からご覧ください。

=============== April 16 Tue===============

キャンパス：三鷹
セミナー名：太陽系小天体セミナー (Solar System Minor Body Seminar)
定例・臨時の別：定例
日時：　4月　16日（火曜日）10時00分～11時30分
場所：zoom
講演者：野上長俊
タイトル：永続痕の発光原理について

世話人の連絡先
-名前：渡部潤一

備考：zoomでの参加

=============== April 17 Wed===============

Campus: Mitaka
Seminar: ALMA-J seminar
Date and time: 2023 Apr. 17 (Wed.), 14:30-15:30 JST
Place: ALMA building, room 102 / Zoom (hybrid)

Speaker: Yao-Lun Yang
Affiliation: RIKEN
Title: Origin of Complex Molecules in Embedded Protostars
Abstract:
Chemical evolution in prestellar and protostellar phases not only determines the initial chemical composition of protostellar disks but also provides a laboratory to study the fundamentals of interstellar chemistry. In recent years, common detection of gas-phase complex organic molecules (COMs) suggests extensive chemical reactions already taken place in the early phase of star formation. However, while some protostars have abundant gas-phase COMs, many protostars still show no sign of COM emission. This contrast of their gas-phase chemical signatures begs the question: Does the diverse gas-phase chemistry represent distinctively different chemical evolution? and what processes govern the chemical evolution in the early phase of star formation? Ice not only represents the more pristine chemistry with minimum contamination from gas-phase reactions but also enables major formation pathways of COMs. While ALMA provides sub-100 au resolution, a resolution necessary to resolve sites of planet formation, to characterize gaseous COMs in nearby embedded protostars, measurements of chemical composition in ices had been limited by low-resolution and limited sensitivity spectroscopy until JWST. Thus, it is imperative to probe both gas and ice chemistry related to COMs, which can only be achieved with both ALMA and JWST. In this talk, I will highlight the latest JWST results of ice chemistry and the characterization of complex ice species in comparison with that detected in gas-phase by ALMA. Particularly, I will present the latest results from the CORINOS program, which aims to delineate the origin of COM diversity in gas-phase. We detect likely features of icy COMs regardless of the presence of gaseous COMs. If these signatures indeed represent icy COMs, we would get similar abundance in ice- and gas-phase. We suggest that these sources have a similar ice chemistry and the apparent deficiency of gaseous COMs is due to inefficient desorption processes. Whereas JWST provides extremely sensitive spectra, interpretations of ice absorption features still face several challenges. The absorption features are intrinsically blended and isolating each species is not trivial. Furthermore, spectra of embedded protostars suffer from substantial extinction by dust and ice, which hinders straightforward measurements of absorption. I will also discuss the approaches we took to mitigate these challenges as well as the limitations.

Facilitator
-Name: Pei-Ying Hsieh

===============April 17 Wed==============

Campus: Mitaka
Seminar: NAOJ Science Colloquium
Date and time: 2023 Apr. 17 (Wed.), 15:30-16:30 JST
Place: the large seminar room / Zoom (hybrid)

Speaker: Haibin Zhang
Affiliation: Division of Science, NAOJ
Title: Circumgalactic Medium and Large Scale Structure at z=2 Traced by Lya Emission
Abstract:
In current pictures of galaxy formation and evolution, galaxies are closely related to their surrounding circumgalactic medium (CGM) and large scale structure (LSS). To investigate the CGM and LSS at high-z, I will introduce our “MAMMOTH-Subaru” paper series that study ~3300 Lyα emitters (LAEs) and ~120 Lyα blobs (LABs; luminous and massive LAEs) at
z=2 selected with Subaru/HSC data. Our main results are: 1. We stack our LAEs to identify the faint Lyα emission in CGM (Lyα halo; LAH). Our LAH is detected till ~100 kpc at the 2σ level and likely extended to ~200 kpc. We show that more massive LAEs generally have more extended
(flatter) LAHs. 2. We find that most (~70%) LABs locate in overdense environments. A unique protocluster region (~40*20 cMpc^2) contains 12 LABs, showing an extremely high LAB number density (>2 times higher than the SSA22 field). We calculate the angular correlation functions of LAEs and LABs, and suggest that LABs are more clustered and likely reside in more massive dark matter halos than LAEs. 3. We calculate the Lyα luminosity function at z=2 and demonstrate an observational approach to measure the cosmic variance. We find that our measurements cannot be explained by previous simulations, and that LAEs likely have a larger cosmic variance than general star-forming galaxies.

Facilitator
-Name: Doris Arzoumanian

Comment: English

===============April 18 Thu==============

Campus： Mitaka
Seminar： Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic： Sporadic
Date and time：18 April (Thu), 15:00-16:30
Place： Insei Seminar Room and Zoom

Speaker：Mr. Junya Natsume
Affiliation：Kyoto University (D1)
Title： Comparison of Spectra of Solar Magnetic Active Phenomena Using Multiple Chromospheric Lines Taken by DST at Hida Observatory

Abstract：

Solar active phenomena can be observed as spatially resolved images while stellar ones cannot. Recently, so-called “Sun-as-a-star analysis” has been conducted on solar active phenomena by spatial integration of solar observation data into data mimicking stellar observations. H-alpha (6563 angstroms) line has been often used for this analysis and analysis including other chromospheric lines will provide more detailed information on dynamics of stellar active phenomena than single line. For example, the simulated He I (10830 angstroms) line in flaring atmosphere with an electron beam produces much stronger emission and absorption than that without an electron beam (Ding et al. 2005). The absorption sensitivity of the He I line increases due to EUV radiation (Fontenla et al. 1993). Ca II K (3934 angstroms) line consists of three components, K1, K2 and K3, ordered from lower to higher formation heights, which exhibit profiles with wide absorption outside, emission inside of K1 and absorption inside of K2, respectively. We observed solar flare and filament activation which occurred at active region NOAA 13078 on 2022 August 19, taken by Domeless Solar Telescope (DST) at Hida Observatory of Kyoto University. Using Horizontal Spectrometer in DST, we obtained imaging spectroscopic data in four chromospheric lines, H-alpha, Ca II K, Ca II IR (8542 angstroms) and He I, simultaneously. The flare ribbons were confirmed in both wings of Ca II K and the line centers of H-alpha, Ca II K and Ca II IR lines while they were weak in He I line. The darkening of the filament activation was confirmed in both wings of H-alpha and He I lines and line centers of all the four lines. We performed Sun-as-a-star analyses on the data and compared spatially integrated spectra in the four lines. The H-alpha line showed brightening near the line center and darkenings in the red and blue wings, whereas the He I line only showed darkenings in both core and wings. On the other hand, the Ca II K line exhibited the darkening coming from the filament activation in the line center and the brightening coming from the flare ribbon in both wings. We also integrated the spectra in wavelength into equivalent width (EW). The EWs around flare peak time had brightening coming from flare ribbon in H-alpha, Ca II K and Ca II IR lines and started darkening 5-10 min after the peak in H-alpha and Ca II K lines coming from the filament activation. The time developments of EWs of H-alpha and Ca II K lines are similar. The EW of He I line started darkening around flare peak time without brightening. The difference between H-alpha and He I lines is caused by the weakness of flare brightening in He I line, which is considered to be contributed to EUV radiation or electron beam. The difference between H-alpha and Ca II K lines is explained by the broad width of K1,2 emission by the flare ribbon at lower altitude and the narrow width of K3 absorption by the filament at higher altitude. Even though the EWs of H-alpha and Ca II K lines are similar, the wavelength from line center of H-alpha and Ca II K had information of line-of-sight velocity and formation heights in this event, respectively.

Facilitator
-Name：Akiko Tei

Comment：Japanese (Slides will be in English)

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

2024.2.19-2024.2.25

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