July 27 Wed 10:30～12:00 SOKENDAI Colloquium zoom
July 27 Wed 14:30～15:30 ALMA J Seminar zoom
July 27 Wed 15:30～17:00 NAOJ Science Colloquium zoom
July 29 Fri 13:30～15:00 Solar and Space Plasma Seminar zoom
詳細は以下をご覧下さい
7月27日（水）
Campus：Mitaka
Seminar：SOKENDAI Colloquium
Regularly Scheduled/Sporadic：Regular
Date and time：July 27th, 2022 10:30-12:00
Place：zoom
Speaker 1: Takumi Kakimoto
Affiliation: SOKENDAI 1st year (M1) (Supervisor: Masayuki Tanaka, Daisuke Iono)
Title: Quiescent Galaxies 1.5 Billion Years after the Big Bang and Their Progenitors
Speaker 2: Yoshihiro Naito
Affiliation: SOKENDAI 1st year (M1) (Supervisor: Hirohisa Hara, Ryoko Ishikawa, Takenori J. Okamoto)
Title: Study of Alfve’n waves in Coronal Hole, the source of the high-speed Solar Wind
Facilitator
-Name：Matsuda, Graduate Student Affairs Unit
7月27日（水）
Campus:Mitaka
Seminar：ALMA-J seminar
Regularly Scheduled/Sporadic:Every Wednesday
Date and Time:2022 July 27 14:30-15:30
Place：Zoom
Speaker：Yu Cheng
Affiliation：NAOJ
Title: Disks, multiplicity and outflows in the intermediate mass star formation region NGC2071IR
Abstract: Intermediate mass protostars, i.e., protostars that will eventually reach final masses of 2–8 Msun, constitute the link between low- and high-mass protostars, and provide a natural laboratory to test star formation theories that unify the two mass regimes. Here I will present our recent ALMA band 6/7 (1.3 mm/0.87 mm) and VLA Ka band (9 mm) observations toward NGC 2071 IR, an intermediate-mass star forming region. These observations allow us to study the dominant luminosity contributors of the region, IRS1 and IRS3, on ~100 au scales. Both sources show strong evidence of disk substructures in the continuum. IRS1 is an intermediate mass protostellar system (3Msun<m<5Msun) with the disk showing a bar-spiral configuration, while IRS3 is a low mass (1.4Msun<m<1.5Msun) close binary system that is in the very early stage of disk fragmentation. For both sources, the inferred ejection directions from different tracers can be strongly misaligned, suggesting jet precession or unresolved multiplicity. The abundant spectral lines allow for a detailed modeling of disk and envelope kinematics. We discuss the implication for the formation and evolution of disks and multiple systems.
Facilitator
Daisuke Iono, Andrea Silva
7月27日（水）
Campus：Mitaka
Seminar：NAOJ Science Colloquium
Regularly Scheduled/Sporadic：Every Wednesday
Date and time：2022 July 27, 15:30-17:00
Place：zoom
Speaker：Yoshida Yuki
Affiliation：NAOJ (D2)
Title：Molecular Dynamics Simulations Explore Dust Monomer Interactions: An Extension of the JKR Adhesion Model
Abstract：Dust is the main material of planets, and grows into planets. The minimum unit of dust is considered to be a sphere 0.1 um in size called a monomer. Monomers grow to cm size by collisional coalescence due to intermolecular forces. However, the growth process is not understood well. The collisional growth process has been studied by laboratory experiments and numerical calculations. In numerical calculations, the JKR theory, which gives the interactions of adhesion, rotation, sliding, and twisting between monomers, is used as the monomer interaction. However, it has been suggested that actual monomers have viscosity so that a part of the kinetic energy of the monomers is converted to that of the molecules (Tanaka et al. 2015). Therefore, it is necessary to extend the JKR theory based on molecular physics.We investigated monomer head-on collision to clarify the adhesion interactions by performing molecular dynamics (MD) simulations and investigated the coeffecient of restitution. We then performed simulations with temperatures and impact velocities to obtain the dependence on the coeffecient of restitution. In this talk, I will present our MD simulation and our recent studies. We found that the coefficient of restitution decreases when the impact velocity is higher than a certain value or when the temperature is higher. In addition, the coefficient of restitution is significantly smaller for higher impact velocity compared to the JKR theory, indicating that collisional physics and the JKR theory are qualitatively different. We, therefore, attempted to modify the JKR theory using the dissipative model of Krijt et al. (2013). We will present these results in detail and propose a new extended theory of JKR theory.
Speaker：Huang Shuo
Affiliation：NAOJ (D2)
Title：Characterizing three serendipitously detected CO emitters
Abstract：I present photometry and SED analysis of three serendipitously detected CO emitters in the SSA22 protocluster field. The single-line CO detection in ALMA band 3 suggests redshift of ~1.4 of two sources and 1.7 of the third source. To examine the redshift and investigate their properties, I perform multiband photometry and SED analysis. All these three sources have Spitzer IRAC counterpart, two of them have MIPS 24 um and/or Herschel detection. Then I check the single-line CO redshift with photometric redshift from SED. I will also discuss the extracted physical properties such as stellar/dust mass and SFR.
Facilitator
-Name：Akimasa Kataoka
Comment：English
7月29日（金）
Campus： Mitaka
Seminar： Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic： Scheduled
Date and time：29 July (金), 13:30-15:00
Place： Zoom
Speaker：吉田南
Affiliation：東京大学
Title：太陽光球面磁場マップが惑星間空間磁場推定に与える影響
Abstract:
太陽表面から太陽圏へと延びる磁場の振る舞いを理解することは、太陽活動が太陽圏や惑星間空間へ与える影響を見積もるために重要なことである。本研究では、太陽から延びる開いた磁場のうち惑星間空間へと広がり惑星間空間磁場となる、オープンフラックスに注目した。太陽光球の磁場マップからコロナ磁場を外挿することで、太陽から1 AU離れた地球近傍での動径方向磁場強度を推定することができる(オープンフラックス推定値)。しかし、オープンフラックス推定値がその場観測で測定されている値に対して2-4分の1程度に過小評価されていることが問題となっている(オープンフラックス問題；Linker et al., 2017)。この問題の原因の一つとして、推定に使用する太陽光球極域磁場が、観測が難しいために過小評価されている可能性が考えられる。
そこで本研究では、推定値と実測値の乖離の原因を探ることを目的に、コロナ磁場モデルに入力する光球の極域磁場と、オープンフラックス推定値との関係を調査した。コロナ磁場モデルにはPotential field source surface(PFSS)モデルとSDO衛星のHMIの磁場マップを用いて、2010年6月から2021年11月の11年間にわたってオープンフラックス推定値を計算した。結果として、双極子磁場構造を持つ極小期と、活動領域の多い極大期では、太陽表面の磁場の構造だけでなく、source surface面(モデル境界面)における磁場強度分布も大きく異なっていることがわかった。極小期のsource surfaceにおける磁場強度は、極域が強く赤道付近が小さい、南北対称の分布、極大期では低緯度に強い磁場がある分布をしていて、極大期では光球の極域磁場強度がオープンフラックスに与える影響は小さいことが示唆された。また、極域磁場強度を人為的に2倍しても、オープンフラックス推定値は測定値に対して、極小期においても10-20%程度の改善であった。以上より、光球磁場の観測が不十分であることは、オープンフラックス問題に対して、極大期では原因とはいえず、極小期でも影響は小さく、主要因とはならないと考えられる。
Facilitator
-Name：川畑佑典
Comment：日本語