カテゴリー: Solar and Space Plasma (SSP) Seminar

Solar and Space Plasma (SSP) Seminar

2024.7.1-2024.7.7

July 1 Mon 15:00-16:30
Solar and Space Plasma Seminar
hybrid; Insei Seminar Room in Subaru Building and Zoom

July 2 Tue 10:00-11:30
太陽系小天体セミナー (Solar System Minor Body Seminar)
Zoom

July 3 Wed 10:00-12:00
SOKENDAI Colloquium
hybrid; Large Seminar Room in Subaru Building and Zoom

July 3 Wed 15:00-16:30
Solar and Space Plasma Seminar
hybrid; Insei Seminar Room in Subaru Building and Zoom

July 3 Wed 15:30-16:30
NAOJ Science Colloquium
Zoom

詳細は下記からご覧ください。

=============== July 1 Mon===============

Campus： Mitaka
Seminar： Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic： Sporadic
Date and time：1 July (Mon), 15:00-16:30
Place： Insei Seminar Room and Zoom

Speaker：Dr. Othman Michel Benomar

Affiliation：NAOJ

Title： Constraining Magnetic Activity Latitudes in Sun-like Stars using asteroseismology

Abstract：
I will discuss a recently developed framework for measuring the activity of Sun-like stars and constraining the latitudes of magnetic activity (Benomar et al. 2023). This framework expresses in a phenomenological manner the effects of activity on low-degree pulsation frequencies, which are global standing waves within stars. Due to various effects, a star is not exactly spherical, and neither is the cavity in which those global modes propagate. The main reason for the departure from sphericity of the mode cavities is the centrifugal force. As this effect is proportional to the square of the rotation rate, it becomes increasingly important as rotation increases. Another cause of asphericity is the magnetic field. A strong magnetic field, such as the one observed in the Sun’s active zones and localized in a specific region of the star, changes the propagation path of the waves and eventually results in a perturbation of the overall cavity shapes of global modes.

Here, I will first show that utilizing a simple single-band activity model on Sun-like stars, it is possible to determine the active latitudes of a star. The method is demonstrated to work on solar data
using the VIRGO instrument aboard the SoHo satellite. I will also show that in an ensemble of 103 Kepler stars, many exhibit signs of activity.

The results indicate a complex pattern of activity bands that essentially depend on stellar effective temperature and stellar rotation. This latter work may provide new insights into the longstanding question about the processes surrounding the dynamo mechanism in other stars.

Facilitator
-Name：Akiko Tei

Comment：Japanese (Slides will be in English)

=============== July 2 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：　7月　2日（火曜日）10時00分～11時30分
場所：zoom
講演者：秋澤宏樹
タイトル: 論文紹介
Abstract:
V.Oldani, et al., Comet 81P/Wild 2: changes in the spin axis orientation during the last five apparitions, Accepted for publication on “Icarus”. https://arxiv.org/abs/2405.19975

世話人の連絡先
-名前：渡部潤一

備考：zoomでの参加

===============July 3 Wed==============

Campus：Mitaka
Seminar：SOKENDAI Colloquium
Regularly Scheduled/Sporadic：Scheduled
Date and time：July 03 10:00-12:00
Place：Large Seminar Room in Subaru Building and Zoom

Speaker：Tadashi Hirose
Affiliation：SOKENDAI 1st year (M1) (Supervisor:Noriyuki Narukage, Takashi Sekii, Masumi Shimojo)
Title：Coronal heating associated with filament eruption

Speaker：Shunsuke Sasaki
Affiliation：SOKENDAI 5th year (D3) (Supervisor:Tomoya Takiwaki, Mami Machida, Takashi Moriya)
Title：Progenitor dependence of core-collapse supernovae

Speaker：Yoshihiro Naito
Affiliation：Not entered
Title：Not entered

Facilitator
-Name：Yoshiaki Sato

Comment：Language: English

===============July 3 Wed==============

Campus： Mitaka
Seminar： Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic： Sporadic
Date and time：3 July (Wed), 15:00-16:30
Place： Insei Seminar Room and Zoom

Speaker：Prof. Petr Heinzel

Affiliation：
Czech Academy of Sciences, Czech Republic
University of Wroclaw, Poland

Title： Do stellar flare fluxes indicate a presence of cool loops ?

Abstract：
On the Sun we routinely resolve the flare ribbons and overlying loop arcades, while stellar fluxes integrate the emission from both. Stellar flare spectra and light curves are usually interpreted in terms of heating of the lower atmospheric layers (ribbons), using the radiation-hydrodynamical simulations (RADYN or FLARIX codes). However, the loop arcades on cool stars are expected to be extended and namely cool loops can thus contribute significantly to flare fluxes. This idea was implemented by Heinzel and Shibata (2018) for Kepler white-light observations. Later on, motivated by TESS observations, MHD simulations of loops have been performed to interpret the observed secondary flare peaks (Yang et al. 2023). The loop arcade was also inferred from time-modulated TESS light curves (Bicz et al. 2023). On the other hand, high-dispersion line spectroscopy shows the signatures of cool-plasma downflows in flare loops which is consistent with the non-LTE radiative-transfer simulations (Wollmann et al. 2023). We will review these new findings and discuss future prospects.

Facilitator
-Name：Akiko Tei

Comment：Japanese (Slides will be in English)

===============July 3 Wed==============

Campus: Mitaka
Seminar: NAOJ Science Colloquium
Date and time: 2024 July 3 (Wed.), 15:30-16:30 JST
Place: Zoom

Speaker: Tetsuya Hashimoto
Affiliation: Department of Physics, National Chung Hsing University
Title: Mysterious fast radio bursts and the new radio telescope in
Taiwan: BURSTT
Abstract:
Fast radio bursts (FRBs) are mysterious coherent radio pulses with millisecond timescales, most of which emerge from galaxies at cosmological distances. Uncovering the origin of FRBs is one of the central foci in astronomy. However, their origin is yet to be known due to the major observational challenge of FRBs: when and where they happen in the sky are unknown. Bustling Universe Radio Survey Telescope in Taiwan (BURSTT) is a new radio array dedicated to detecting mysterious FRBs in the nearby Universe. Within a few years, BURSTT will overcome this observational challenge with its unique capabilities of nearly all-sky monitoring (10,000 deg2) and accurate localization (< 1 arcsec), and none of the current FRB facilities have both of these capabilities.
In this presentation, I will summarize the expected science cases with unique FRB samples of BURSTT. In contrast to the current FRB facilities, BURSTT will observe the same sky as multi-messenger instruments, including gravitational waves and neutrinos. This BURSTT’s design will maximize the chance of the simultaneous detection of multi-messengers or multi-wavelength counterparts, which would strongly constrain the FRB progenitor scenarios. BURSTT will provide a unique window into FRB applications from environments, progenitors, to cosmology.

Facilitator
-Name: Shubham Bhardwaj

Comment: English

2024.6.24-2024.6.30

June 25 Tue 10:30-12:00
Solar and Space Plasma Seminar
hybrid; Seminar Room 310 in Main building (North) and Zoom

June 26 Wed 10:00-12:00
SOKENDAI Colloquium
hybrid; Large Seminar Room in Subaru Building and Zoom

June 26 Wed 14:30-15:30
ALMA-J seminar
hybrid; Room 102 in ALMA building and Zoom

June 26 Wed 15:30-16:30
NAOJ Science Colloquium
hybrid; Rinkoh Seminar Room and Zoom

June 28 Fri 15:30-16:30
NAOJ Seminar
hybrid; Large Seminar Room in Subaru Building and Zoom

詳細は下記からご覧ください。

=============== June 25 Tue===============

Campus： Mitaka
Seminar： Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic： Sporadic
Date and time：25 June (Tue), 10:30-12:00
Place： Seminar Room 310 in Main building (North) and Zoom

Speaker：Dr. Gabrial Giono

Affiliation：Space Research Institute, Austrian Academy of Sciences, Austria

Title： Plasma and planetary science instrumentation at the IWF: SMILE, Comet Interceptor, JUICE and BepiColombo

Abstract：
The Institut für Weltraumforschung (IWF) in Graz, Austria, has been developing space instruments for more than 50 years. In recent years, the institute has been contributing to a number of plasma and planetary missions. This talk will focus on four missions: (1) the ESA/CAS Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) mission, (2) the ESA Comet Interceptor mission, (3) the ESA JUICE mission, and (4) the ESA/JAXA BepiColombo mission.
An overview of the IWF instrumental contribution for each these four missions will be presented, respectively (1) the EBOX for the Soft X-ray imager, (2) the MANiaC mass spectrometer and DFP flux-gate magnetometers, (3) the MAGSCA scalar optical magnetometer and (4) the PICAM ion mass spectrometer. For each instrument, an in-depth explanation of their working principle will be provided.

Facilitator
-Name：Akiko Tei

Comment：Japanese (Slides will be in English)

=============== June 26 Wed===============

Campus：Mitaka
Seminar：SOKENDAI Colloquium
Regularly Scheduled/Sporadic：Scheduled
Date and time：Jun 26 10:00-12:00
Place：Large Seminar Room in Subaru Building and Zoom

Speaker：Naoya Kitade
Affiliation：SOKENDAI 1st year (M1) (Supervisor:Akimasa Kataoka, Hideko Nomura, Yuka Fujii)
Title：Support for fragile porous dust in a gravitationally self-regulated disk around IM Lup (review of a paper by Ueda et al, 2024 2406.07427)

Speaker：Chiba Rhotaro
Affiliation：Not entered
Title：Not entered

Speaker：Shotaro Tada
Affiliation：SOKENDAI 5th year (D3) (Supervisor:Takayuki Kotani, Yutaka Hayano, Yosuke Minowa)
Title：Exploring Exoplanetary Atmosphere Asymmetries Through Transmission Spectroscopy: Application to JWST NIRSpec/G395H Data of WASP-39 b’s Transit

Facilitator
-Name：Yoshiaki Sato

Comment：Language: English

===============June 26 Wed==============

Campus: Mitaka
Seminar: ALMA-J seminar
Date and time: 2024 June 26 (Wednesday), 14:30-15:30 JST
Place: Room 102 in ALMA building / Zoom (hybrid)
Speaker: Dirk. Petry (European Southern Observatory)

Title: Results from the ALMA internal development study on uv coverage assessment and scheduling

Abstract: This development study started in 2020 and has now submitted its final report to the review panel. In this talk I will present a “sneak preview” of the results which consist mostly of suggestions for adjustments to ALMA scheduling, QA0, and QA2 to achieve better uv coverage and image quality. I will also introduce our new uv coverage QA tool “assess_ms”.

Facilitator
-Name: Pei-Ying Hsieh

===============June 26 Wed==============

Campus: Mitaka
Seminar: NAOJ Science Colloquium
Date and time: 2024 June 26 (Wed.), 15:30-16:30 JST
Place: the rinkoh seminar room / Zoom (hybrid)

Speaker: Shigeo Kimura
Affiliation: Tohoku University
Title: Pursuing Sources of Cosmic High-energy Neutrinos
Abstract:
Cosmic high-energy neutrinos are expected to be a smoking-gun signature to identify the origin of high-energy cosmic rays. IceCube experiment reported detection of cosmic high-energy neutrinos in 2013, the origin of which became a new mystery in astrophysics. In order to identify the cosmic neutrino sources, multi-messenger observational and analysis technics are now rapidly developing. In this talk, I will review the progress of high-energy neutrino astrophysics, discuss high-energy neutrino emission model in radio-quiet active galactic nuclei, and introduce our effort to identify neutrino sources using optical observational data.

Facilitator
-Name: Ryotaro Chiba

Comment: English

===============June 28 Fri==============

Campus：Mitaka
Seminar：NAOJ Seminar
Regularly Scheduled/Sporadic：Regular
Date and time：June 28, 2024 15:30-16:30
Place：Zoom/Large Seminar Room (hybrid)

Speaker：Dr. Jose Luis Gómez
Affiliation：Instituto de Astrofísica de Andalucía

Title：Eyes on the Invisible: Charting New Horizons with the Event Horizon Telescope

Abstract:The Event Horizon Telescope (EHT) collaboration has captured the first image of a black hole’s event horizon in the galaxy M87, and subsequently, in the supermassive black hole at the center of our Milky Way, SgrA. More recently, the collaboration has released the first follow-up image of M87, utilizing observations from April 2018. The EHT has also revolutionized our understanding of the relativistic jets commonly present in active galactic nuclei, revealing the processes governing the jet formation, collimation and acceleration with an unprecedented angular resolution. The upcoming next-generation Event Horizon Telescope (ngEHT) is poised to significantly upgrade the current system by adding new stations and introducing multi-frequency observational capabilities. These will notably improve the ngEHT’s angular resolution, dynamic range, and overall coverage. This expansion is crucial for enabling the ngEHT to create the first movies of black holes, a leap forward in understanding the processes of black hole accretion and the formation of relativistic jets. In addition, the ngEHT’s advanced features will be instrumental in exploring alternative theories to General Relativity and will expand our observational reach to include potentially a dozen new black holes. By adding an orbiting antenna, the Black Hole Explorer (BHEX), a potential NASA mission, will discover and measure the bright and narrow “photon ring” that is predicted to exist in images of black holes, and fully encodes the space-time metric.

Facilitator
-Name：Takashi Moriya

2024.6.10-2024.6.16

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

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

June 12 Wed 15:30-16:30
NAOJ Science Colloquium
hybrid; Large Seminar Room in Subaru Building and Zoom

June 13 Thu 14:30-15:30
ALMA-J seminar
hybrid; Room 102 in ALMA Building and Zoom

June 14 Fri 13:30-14:30
ATCセミナー
hybrid; Large Seminar Room in Subaru Building and Zoom

June 14 Fri 15:30-16:30
NAOJ Seminar
hybrid; Large Seminar Room in Subaru Building and Zoom

June 14 Fri 15:30-17:00
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。

=============== June 11 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：　6月　11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: 研究紹介

世話人の連絡先
-名前：渡部潤一

備考：zoomでの参加

=============== June 12 Wed===============

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

Speaker：Takumi Kakimoto
Affiliation：SOKENDAI 3rd year (D1) (Supervisor: Masayuki Tanaka, Daisuke Iono, Kiyoto Yabe)
Title：The role of the environment in quenching of massive galaxies at high redshifts

Speaker：Kazuki Watanabe
Affiliation：SOKENDAI 2nd year (M2) (Supervisor: Tai Oshima, Yoshinori Uzawa, Takafumi Kojima)
Title：Development of a sub-THz MKID Camera for Deep Space Observation

Facilitator
-Name：Yoshiaki Sato

Comment：Language: English

===============June 12 Wed==============

Campus: Mitaka
Seminar: NAOJ Science Colloquium
Date and time: 2024 June 12 (Wed.), 15:30-16:30 JST
Place: the large seminar room / Zoom (hybrid)

Speaker: Mehrnoosh Tahani
Affiliation: Stanford University
Title: Galactic Structure and Evolution: What 3D Magnetic Field Observations Are Revealing
Abstract:
Recent observations have significantly advanced our understanding of the three-dimensional (3D) structure and evolution of the interstellar medium (ISM). To fully comprehend ISM evolution, however, it is necessary to study interstellar magnetic fields, which play a pivotal role in the evolution of the galaxy and the formation of stars. Despite their importance, our understanding of magnetic fields in the ISM is limited due to significant challenges in observing them in 3D. In this talk, I will briefly discuss how we overcame the challenges in determining the 3D magnetic fields associated with giant molecular clouds. These 3D fields enabled us to propose step-by-step scenarios to explain the formation of these clouds, revealing previously undiscovered interstellar structure. Our approach involves a novel technique based on Faraday rotation measurements to detect the line- of-sight component of magnetic fields. We then integrate these line-of-sight measurements with plane-of-sky magnetic field observations to examine the 3D magnetic field morphology associated with the clouds. Finally, we employ Galactic magnetic field models to reconstruct the complete 3D magnetic field morphologies of these clouds, including their previously unknown direction. These 3D studies provide novel constraints on theories for the formation and evolution of star-forming clouds.

Facilitator
-Name: Nanase Harada

Comment: English

===============June 13 Thu==============

Campus: Mitaka
Seminar: ALMA-J seminar
Date and time: 2024 June 13 (Thursday), 14:30-15:30 JST
Place: Room 102 in ALMA building / Zoom (hybrid)
Speaker: Nimesh Patel
Affiliation: Harvard-Smithsonian Center for Astrophysics

Title: Chemical Evolution from AGB stars to Planetary Nebulae: A spectral-line survey of the Egg Nebula (CRL 2688)
Abstract:
Carbon-rich stars on the asymptotic giant branch (AGB) are major sources of gas and dust in the interstellar medium. AGB stars remain
in this stage for 1 to 10 Myrs, and have typical masses of 1–8 Msun and mass loss rates of 10^(−7) to 10^(−4) Msun/yr. During the
brief (∼1000 yr) period in the evolution from the AGB to Planetary Nebula (PN) there is a dramatic change in the morphology from nearly
spherical symmetry to bipolar, quadrupolar and more complex structures.
Because of the brief duration of this Proto-Planetary Nebula (PPN) phase and the poor angular resolution of most prior molecular line
observations (>= 15″– 20″), the physical mechanisms governing the AGB -> PPN -> PN transition and the accompanying chemical processes
are poorly understood.

Using the Submillimeter Array (SMA), we have previously carried out spectral-line surveys of CRL 618, NGC 7027, and IRC+10216. In this
talk, I will present preliminary results from a spectral-line survey of CRL2688 (Egg Nebula), which is a well known PPN with multiple
outflows and shell-like structures discovered in HST images.
Together, these unbiased surveys of the 4 prototypical carbon rich objects which span the evolutionary sequence from the AGB to fully
formed planetary nebula — IRC+10216 (AGB), CRL 2688 (early PPN), CRL 618 (PPN) and NGC 7027 (PN) — have the potential of unravelling
the physical and chemical evolution of circumstellar envelopes from AGB to PN.

The SMA line survey of CRL 2688 covers the frequency range of 224–266 GHz, with an rms noise level of 100~150 mJy/beam in 1 km/s
wide channels. About 130 lines are detected in the 42 GHz coverage; all the detected lines have been identified. Lines of silicon
bearing species such as SiCC and SiS are much weaker (compared to those seen in IRC+10216). Several lines show morphological features
corresponding to the multiple outflows in this source (HCN, CS), and the disk like structure (CH3CN,SiS). The channel maps show an
S-shaped morphology for the bipolar lobes in CS and HCN, clear indication of a precessing/wobbling jet or two jets with different
axes. It is interesting to see Si bearing molecules, and weak lines of c-C3H2 in CRL 2688, whereas this molecule is one of the most
abundant in CRL 618 (with more than 150 lines in that survey). Maps of a few of the trace species — the first images obtained for most
of these — reveal diverse angular distributions, allowing us to distinguish the different regions in which each species is present
in this complex source.

Facilitator
-Name: Pei-Ying Hsieh

===============June 14 Fri==============

キャンパス：三鷹
セミナー名：ATCセミナー
定例・臨時の別：臨時
日時：6月14日（金曜日）13時30分～14時30分
場所：大セミナー室 + Zoom

講演者： Pradip Gatkine 氏
所属： UCLA
タイトル：Astronomical instruments on a chip – Getting ready for the next-generation telescopes

Abstract：
Astrophotonics is the application of versatile photonic technologies to channel, manipulate, and disperse guided light from one or more telescopes to achieve scientific objectives in astronomy in an efficient and cost-effective way. The photonic platform of guided light in fibers and waveguides has opened the doors to next-generation instrumentation for both ground- and space-based telescopes in optical and near/mid-IR bands, particularly for the large and extremely large telescopes (ELTs). Utilizing the photonic advantage for astronomical spectroscopy is a promising approach to massively miniaturize the next generation of spectrometers for large ground- and space-based telescopes. In this talk, I will discuss some of the recent results from our efforts to design and fabricate high-throughput on-chip spectrometers based on Arrayed Waveguide Gratings (AWG). These devices are ideally suited for capturing the AO-corrected light and enabling exciting science cases, such as measuring exoplanet masses and characterizing exoplanet atmospheres. I will also discuss specific approaches to make this technology science-ready for the ELT era.

世話人の連絡先
-名前：永井　誠

備考：英語での講演。

===============June 14 Fri===============

Campus：Mitaka
Seminar：NAOJ Seminar
Regularly Scheduled/Sporadic：Regular
Date and time：June 14, 2024 15:30-16:30
Place：Zoom/Large Seminar Room (hybrid)

Speaker：Dr. Nimesh Patel
Affiliation：Center for Astrophysics/ Harvard University

Title：Building the Next Generation Event Horizon Telescope

Abstract:The next-generation Event Horizon Telescope (ngEHT) will be a transformative upgrade to the EHT, that will allow us to create time-lapse movies of supermassive black holes (SMBHs) at event horizon scales. By enhancing the angular resolution, dynamic range, and improved temporal coverage, the ngEHT promises a new era of discovery in black hole science, allowing us to study strong-field gravity features predicted by General Relativity (GR), active accretion, and relativistic jet launching processes. The ngEHT program aims to achieve these goals by adding four 10m-class submillimeter dishes at new geographic locations around the globe, for improved spatial frequency coverage. Several of the existing EHT stations will have upgraded receivers and fore-optics for simultaneous multifrequency observations (86, 230 and 345 GHz), and new backends and data recorders with significantly higher data rates (up to 320 Gb/s). The ngEHT will allow longer duration high cadence observations allowing creation of movies of black holes and jets. This talk will describe the ngEHT’s technical plans, design considerations, station siting, and the project’s timeline.

Facilitator
-Name：Takashi Moriya

=============== June 14 Fri===============

Campus： Mitaka
Seminar： Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic： Sporadic
Date and time：14 June (Fri), 15:30-17:00
Place： Insei Seminar Room and Zoom

Speaker：Dr. Alexei Pevtsov
Affiliation：National Solar Observatory
Title： Integrated Synoptic Program at the US National Solar Observatory and ngGONG

Abstract：

Providing the background synoptic observations to characterize the variable solar activity and operating ground-based facilities to enable
such long-term observations are two key aspects of the US National Solar Observatory (NSO) mission, which are entrusted to NSO’s Integrated
Synoptic Program (NISP). The program operates two facilities: Global Oscillation Network Group (GONG) and Synoptic Optical Long‐term
Investigations of the Sun (SOLIS). Data from these facilities are provided to research and space weather operation communities. This talk
will overview the Program activities, provide status of GONG and SOLIS facilities, and discuss their future replacement – a ground-based
network of robotic instruments provisionally called next generation GONG (ngGONG).

Facilitator
-Name：Akiko Tei

Comment：Japanese (Slides will be in English)

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)

2024.3.18-2024.3.24

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

March 19 Tue 10:00-11:30
太陽系小天体セミナー
Zoom

March 22 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 18 Mon===============

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

Speaker：Mr. Takero Yoshihisa
Affiliation：Kyoto University (M2)
Title： One-dimensaional MHD simulation for prominence formation triggered by single heating event

Abstract：

I will review on the thermal non-equilibrium phenomena in the solar atmosphere, and present on my master thesis.
Plasma condensation phenomena in the corona, such as prominences and coronal rain, have been observed for many years. It is not clear whether current models can explain their formation process. In one of the proposed models that explain observational properties, the “evaporation condensation” model, a steady or quasi-steady heating at footpoints of a loop drives dense plasma evaporation into the corona and triggers the condensation.
However, it is natural to think of such steady or quasi-steady heating as the superposition of multiple heating events occurring between multiple magnetic field lines. When studying physical processes along a single magnetic field line, a single heating event should be considered as the basic unit.
We therefore investigate whether condensation occurs when the non-steady single heating event occurs at footpoints of a coronal loop. For this purpose, we set a dipped loop and solve 1.5-dimensional (one-dimensional three-vector components) magnetohydrodynamic equations, including radiative cooling, thermal conduction, gravity, and phenomenological turbulence heating. After reproducing the corona by energy input from imposed velocity perturbation at the footpoints, prominence formation is investigated by adding artificial transient localized heating. It is found that required amount of the heating per unit of time is ∼ 10^3 times larger than in steady cases. The amount of energy reaches nanoflare class. We also perform a parameter survey varying the magnitude of the localized heating rate to investigate the conditions for condensation by transient localized heating. The results show that with sufficiently strong heating, sufficient plasma is supplied to the corona to allow cooling to proceed and condensation to occur. It is essential that the loop temperature decreases and thermal conduction becomes inefficient with respect to cooling. Using the loop length L and the Field length λF, the condition for condensation is expressed as λF ≲L/2 under conditions where cooling exceeds heating.

Facilitator
-Name：Akiko Tei

Comment：Japanese (Slides will be in English)

=============== March 19 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19日（火曜日）10時00分～11時30分
場所：zoom
講演者：大坪貴文

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 22 Fri==============

Campus：Mitaka
Seminar：NAOJ Seminar
Regularly Scheduled/Sporadic：Regular
Date and time：March 22, 2024 16:00-17:00
Place：Zoom/Large Seminar Room (hybrid)

Speaker：Director General, Dr. Saku Tsuneta
Affiliation：National Astronomical Observatory of Japan

Title：素晴らしく面白かった太陽の研究
＝40年の研究生活を振り返って＝

Abstract: これまで約40年近く、大学院生や仲間の研究者の方々と、「ひのとり」の硬Ｘ線望遠鏡、「ようこう」の軟Ｘ線望遠鏡、「ひので」の可視光望遠鏡といった飛び道具に載せる望遠鏡の開発を行ってきました。翔体実験装置の開発をするには、教科書を読むだけでは不十分で、観測装置の構想から設計、製作、試験、打上げ前不具合の徹底追及、そして打上げ、飛翔結果を解析して初めて一人前になれます。衛星実験では規模が大きく開発期間も長いため、この過程を経験することが難しく、衛星実験の合間にロケット実験や気球実験も行ってきました。
談話会では、プロジェクトの立ち上げ方や進め方について自分の経験をもとに論じるのと同時に、国立天文台での6年間について所感を述べたいと思います。

Facilitator
-Name：Fumitaka Nakamura