May 18 Tue 10:00～11:30 太陽系小天体セミナー / Solar System Minor Body Seminar zoom
June 16 Wed 15:30～17:00 NAOJ Science Colloquium zoom
June 18 Wed 13:30～15:00 Solar and Space Plasma Seminar zoom
June 18 Wed 16:00～17:00 NAOJ Seminar zoom
詳細は以下をご覧下さい
6月15日（火）
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：6月15日（火曜日）10時00分～11時30分
場所：zoom
講演者：大澤亮
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
6月16日（水）
Campus：Mitaka
Seminar：NAOJ Science Colloquium
Regularly Scheduled/Sporadic：Every Wednesday
Date and time：2021 June 16, 15:30-17:00
Place：zoom
Speaker：Huang Shuo
Affiliation：NAOJ （D1 student）
Title：Dust-to-stellar mass ratio in 162 dusty star-forming galaxies
Abstract：Dust absorbs radiation at short wavelengths and re-emit the energy at far-infrared and plays an important role in physical processes in the interstellar medium. It is suggested that dust-to-stellar mass ratio can be used to probe evolutionary states of star-forming galaxies. In this talk I introduce the SED analysis of 162 dusty star-forming galaxies (DSFGs) selected by 1.1 mm ALMA observations. Using the latest modelling and fitting techniques to analyze the multiwavelength dataset, I derive the dust mass together with other physical properties. The negative correlation between M_dust/M_star and age in post-starburst galaxies is also present in massive galaxies that are still actively forming stars. The distance above the star-forming main sequence decreases with increasing age. Such results may reflect a smooth evolution of DSFGs’ physical properties.
Speaker：Yudong Luo
Affiliation：NAOJ （D3 student）
Title：Funny story about the big-bang nucleosynthesis constraints on the primordial black holes
Abstract：In this talk, I will show the constraints on the primordial black holes (PBHs) via studying the photodisintegration process triggered by the Hawking radiation.We calculate the nuclear photodisintegration rates with a nonthermal photon spectrum derived by solving the Boltzmann equation iteratively. The exact spectrum is much different than that based on an often-used analytical bended power-law spectrum and it is found to significantly depend on the adopted PBH mass functions. With the newest observational limit on the 3He abundance in Galactic H II regions, the updated 3He constraints on PBH mass spectrum in the horizon mass range 1012–1013 g are derived. Our results show that 3He constraints on the critical mass function are about one order of magnitude severer than the monochromatic one although the fraction of PBHs in the low-mass tail region is relatively small. The 6Li elemental abundance is also enhanced significantly for the critical mass function. More precise measurement of 6Li abundance is highly desirable to provide a promising constraint on PBHs in the future. For monochromatic mass function, we provide the analytical bounds for photodisintegration and hadrodissociation from PBH radiation, and we report discrepancies between our updated 3He constraints and the previous results.
Facilitator
-Name：Akimasa Kataoka
Comment：English
6 月18日（金）
Campus： Mitaka
Seminar： Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic： Scheduled
Date and time：18 June (Fri), 13:30-15:00
Place： zoom
Speaker：Kosuke Namekata
Affiliation： NAOJ
Title：The quest for filament eruptions on active M/G-type stars as an indicator of stellar CMEs
Abstract：
Solar flares are often accompanied by filament/prominence eruptions, sometimes leading to coronal mass ejections (CMEs). On active stars, larger `superflares’ are sometimes observed, which can severely affect the exoplanet habitability. However, the association of stellar filament eruptions/CMEs is little known. Optical spectroscopic observation of Balmer-lines is one of the promising ways to detect stellar filament eruptions. We have conducted time-resolved spectroscopic observations of the H-alpha line of active M-G dwarfs with our 3.8-m Seimei Telescope. With the high time cadence (~1 min) and high quality (S/N>100) data, we have detected a blue-shifted H-alpha absorption component during a superflare on young solar-type star EK Draconis as evidence of stellar filament eruption; this is the first detection for solar-type (G-type) stars. The velocity ~510 km/s and length scale ~500 Mm was very large, and its mass was more than 10 times larger than the largest solar CMEs, indicating that the associated CME can have a significant impact on exoplanet environment. Furthermore, we have detected blue-shifted H-alpha emission profiles during flares on M-dwarfs (red, cooler stars), as recently other researches have also reported (e.g. Vida et al. 2016). Although its origin has been controversial, I will discuss a possible relation with prominence/filament eruptions on cooler dwarfs. Further study will be able to constrain the effect of filament eruptions/CMEs on exoplanet environments around active stars and stellar mass/momentum evolution.
Facilitator
-Name：Munehito Shoda
6 月18日（金）
Campus：Mitaka
Seminar：NAOJ Seminar
Regularly Scheduled/Sporadic：Scheduled
Date and time：2021 June 18, 16:00～17:00
Place：zoom
Speaker：大坪 貴文 / Ootsubo, Takafumi（国立天文台天文データセンター / Astronomy Data Center,NAOJ)
Affiliation：
Title：すばる望遠鏡中間赤外線観測が明らかにする彗星の起源と熱履歴
Abstract：
彗星や小惑星などの太陽系小天体は、太陽系形成時に作られ原始太陽系円盤の
多くの情報を保持していると期待される。以前は彗星と小惑星は異なる領域で
形成されたと考えられていたが、近年では小惑星軌道で彗星活動を見せる
活動的小惑星の発見などもあり、その境界および起源と履歴を調べることは、
太陽系進化を理解するという点でも重要性が増してきている。
今回我々は、すばる望遠鏡でパンスターズ彗星 (P/2016 BA14) の中間赤外線
観測をおこない、これまで彗星には殆ど存在しないと考えられていた含水鉱物
の存在を初めて観測的にとらえ、過去にこの彗星が、現在の軌道で予想される
よりも高い温度に加熱された履歴があることを明らかにした。我々は、これまで
約15年にわたり、すばるの中間遠赤外線装置COMICSを用いて彗星のケイ酸塩鉱物・
有機物探査を続けてきたが、その成果を踏まえて、今回の含水鉱物の検出の
位置づけと今後の展望についても紹介したい。
Facilitator
-Name： 尾崎 忍夫 / Ozaki, Shinobu