Home > ALMA Jセミナー | Solar and Space Plasma (SSP) Seminar | その他 | 太陽系小天体セミナー | 科学研究部コロキウム > 2021.6.28-2021.7.4


Jun 29 Tue 10:00~11:30  太陽系小天体セミナー / Solar System Minor Body Seminar zoomun

Jun 29 Tue 10:00~11:30  博士後期課程中間報告会      zoom    

Jun 30 Wed 15:00 ~16:00 ALMA-J seminar           zoom

Jun 30 Wed 15:30~17:00  NAOJ Science Colloquium      zoom

Jul 2 Fri 13:30~15:00  Solar and Space Plasma Seminar    zoom       






日時: 6月29日(火曜日) 13時~14時40分(予定)
場所:Zoom (接続先情報は大学院係にお問い合わせください)

講演者:Yongming Liang (13:00~)
所属:総研大 天文科学専攻
タイトル:Correlation between galaxy and IGM at z≈2 mapped by Subaru/HSC

講演者:竹村 英晃 (13:50~)
所属:総研大 天文科学専攻

-名前:松田 幸恵


Campus: Mitaka
Seminar: ALMA-J seminar
Date and Time: 2021 June 30, 15:00-16:00
Place: Zoom
Speaker:Nanase Harada
Title:A wide-frequency molecular line survey in the starburst galaxy NGC 253 (ALCHEMI)
Abstract:Astrochemistry has been widely used as a tool to study the properties of the molecular interstellar medium. However, astrochemical studies in external galaxies have been difficult before ALMA because of the limited sensitivity and angular resolution. Thanks to ALMA, it has been shown that many molecular species are detectable in the spatially resolved way even in external galaxies, which means that we can resolve regions with high activities of star formation or AGN activities. Taking an advantage of this opportunity, we conducted the wide-frequency (289 GHz wide) line survey called ALMA Comprehensive High-resolution Extragalactic Molecular Inventory (ALCHEMI), one of the ALMA Large Programme in Cycle 5 to observe the center of the prototypal starburst galaxy NGC 253. In our survey, we have detected many complex organic molecules, including first detections in external galaxies. In Galactic sources, these molecules are usually abundant in protostellar cores, but we detect these species even in the 100-pc scale, suggesting hot and dense environment in the center of NGC 253. Our analysis of radicals (unstable molecules) also suggested that the cosmic-ray ionization rate is about 3 orders of magnitude higher than the Galactic spiral-arm regions from the active star formation in this galaxy, providing higher pressure into the interstellar medium.
Facilitator: Yuichi Matsuda, Yusuke Miyamoto


Seminar:NAOJ Science Colloquium
Regularly Scheduled/Sporadic:Every Wednesday
Date and time:2021 June 30, 15:30-17:00
Speaker:Yuichi Ito
Title:Mineral Atmosphere of Hot Rocky Exoplanet
Abstract:In near future, planed space missions such as JWST and Ariel would open a new era of characterization of close-in rocky exoplanets. Also, about 500 exoplanets whose radii are less than 2 Earth radii have radiative equilibrium temperatures high enough to melt and vaporize rock. Thus, if rocky and dry, they likely have atmospheres composed of rocky materials such as Na and SiO. I call such atmospheres mineral atmospheres. In this talk, I will show the one-dimension theoretical thermal structures and also photo-evaporation efficiency of mineral atmospheres (Ito et al. 2015, 2021, Ito & Ikoma 2021). In addition, I will show that our feasibility assessment demonstrates that secondary transit measurements with planed space telescopes can distinguish mineral atmospheres from volatile-rich atmospheres.
-Name:Akimasa Kataoka


Campus: Mitaka
Seminar: Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic: Scheduled
Date and time:02 July (Fri), 13:30-15:00
Place: zoom
Speaker:Ryohtaroh Ishikawa
Affiliation: NAOJ/SOL
Title:Multi-scale deep learning for estimating horizontal velocity fields on the solar surface

The dynamics in the photosphere is governed by the turbulent convective motion called granulation. It is important to derive three dimensional velocity vectors to know nature of the turbulent convection and to evaluate the vertical Poynting flux toward the upper atmosphere. The line-of-sight component of the velocity can be obtained by observing the Doppler shifts, but it is difficult to obtain the velocity component perpendicular to the line-of-sight which corresponds to the horizontal velocity in disk center observations.
We develop a convolutional neural network model with a multi-scale deep learning architecture which consists of multiple convolutional kernels with various sizes of the receptive fields and performs convolution for both the spatial and temporal axes. The network is trained with data from three different numerical simulations of turbulent convection. We also newly introduce the coherence spectrum to assess the horizontal velocity fields thus derived at each spatial scale.
The multi-scale deep learning method successfully predicts the horizontal velocities for each convection simulation in terms of the global-correlation-coefficient. However, the coherence spectrum reveals the strong dependence of the correlation coefficients on the spatial scales. By comparing the result of the three convection simulations, we find that this decrease of the coherence spectrum occurs at around the energy injection scales.
These results imply that the accuracy for the small-scale structures is not guaranteed only by the global-correlation-coefficient. To improve the accuracy in small-scales, it may be worth to improve the loss function to enhance the small-scale structures and to utilize other physical quantities as input data related to the non-linear cascade of convective eddies.

-Name:Munehito Shoda

Home > ALMA Jセミナー | Solar and Space Plasma (SSP) Seminar | その他 | 太陽系小天体セミナー | 科学研究部コロキウム > 2021.6.28-2021.7.4

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