Nov 24 Wed 15:30～17:00 NAOJ Science Colloquium zoom
Nov 26 Fri 13:30～15:00 Solar and Space Plasma Seminar zoom
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11月24日（水）
Campus：Mitaka
Seminar：NAOJ Science Colloquium
Regularly Scheduled/Sporadic：Every Wednesday
Date and time：2021 Nov. 24, 15:30-17:00
Place：zoom
Speaker：Takemura Hideaki
Affiliation：D2
Title：The possibility of core growth with mass accretion and the core mass calculation method for continuum observations
Abstract：Stars are formed in dense regions which are called dense cores in the molecular clouds. Thus, it is crucial to understand how dense cores form from parental molecular clouds to reveal star formation processes. Since the evolution process of a star strongly depends on the mass, the mass is one of the most important properties of a dense core as well. The mass functions of dense cores (CMFs), the mass spectrum of dense cores, are expected to have information of the core evolution and star formation processes. Many previous studies of CMFs toward nearby star-forming regions with single-dish telescopes have suggested that the CMFs resemble the stellar IMFs. However, top-heavy CMFs are reported from recent ALMA observations toward distant high-mass star-forming regions. Therefore, the processes that link CMF and IMF have not been revealed. In this presentation, I will discuss the possibility of core growth suggested from the comparison of CMF and IMF in the Orion Nebula Cluster region and the core mass calculation method for dust continuum observation of ALMA.
Speaker：Kashiwagi Raiga
Affiliation：D1
Title：The Role of Filament-Filament Collision in Star Formation
Abstract：Filamentary structures are recognized as a fundamental component of interstellar molecular clouds in observations made by the Herschel satellite. In addition, most of the prestellar cores that will become protostars in the future have been found along gravitationally unstable filaments. Based on these observational results, the relationship between filaments and star formation has attracted much attention. Recently, some observations imply that star formation is caused by filament-filament collisions. However, theoretical predictions are still insufficient: how they will evolve and which physical parameters change their evolution. Thus, We are challenging the theoretical understanding of filament-filament collisions by using numerical calculation. In this seminar, I will report the first result of a 2d-hydrodynamical simulation that investigated evolutions of filament-filament collisions and what parameters controlled their evolution.
Facilitator
-Name：Akimasa Kataoka
Comment：English,
11月26日（金）
Campus： Mitaka
Seminar： Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic： Scheduled
Date and time：26 November (Fri), 13:30-15:00
Place： zoom
Speaker：正木寛之
Affiliation：千葉大学
Title：数値シミュレーションと機械学習を組み合わせた太陽表面の速度場・磁場推定
太陽の放射強度、視線方向磁場、視線方向速度場のスナップショットを用いて
太陽表面の水平速度場、水平磁場を予測するニューラルネットワークを開発した。
太陽ではこれまでに高精度な望遠鏡、衛星を用いた多くの観測が行われている。
しかし観測精度が十分でない物理量や、原理上、直接観測できないものなどもあり
すべての太陽のデータを得ることはできない。そこで本研究ではシミュレーションと
ディープラーニングを組み合わせることにより、このような観測が難しい物理量を
人工知能の高い推測能力によって放射強度など観測が容易な物理量から評価する手法を開発した。
現在までに太陽表面での水平速度場と水平磁場の予測を行っており、
シミュレーションデータとネットワークの推定したデータとの間の相関係数として、
水平速度場では0.7、水平磁場では0.6を達成している。
Facilitator
-Name：Takayoshi oba
Comment：in English
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