カテゴリー: 太陽系小天体セミナー

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

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

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

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

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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)