February 6 Tue 10:00-11:30
太陽系小天体セミナー
Zoom
February 7 Wed 14:00-15:00
ALMA-J seminar
hybrid; Small seminar room in the Subaru building and Zoom
February 7 Wed 15:30-16:30
NAOJ Science Colloquium
hybrid; Large Seminar Room in Subaru Building and Zoom
February 9 Fri 10:30-12:00
Solar and Space Plasma Seminar
Zoom
February 9 Fri 16:00-17:00
NAOJ Seminar
hybrid; Large Seminar Room in Subaru Building and Zoom
詳細は下記からご覧ください。
=============== February 6 Tue ===============
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：2月6日（火曜日）10時00分～11時30分
場所：zoom
講演者：和田 空大
所属：東京大学
タイトル：Tomo-e Gozen NEO 探査改善プロジェクトの現状共有と今後の展望
Abstract：東京大学木曽観測所では2019年から地球接近小惑星 (NEOs)
の探査を開始し、現在までで多数の小惑星の発見や物理量の測定を行ってきました。
探査を行うにつれ現在のプロセスの課題が浮き彫りになっており、私が主導して改善を試みている最中です。
今回の発表では、プロセス全体の中でも特に移動天体検出に使っている機械学習モデルについて、その改善の方針と現状共有をします。
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
=============== February 7 Wed ===============
Campus: Mitaka
Seminar: ALMA-J seminar
Date and time: February 7 (Wed) 14:00-15:00
Place: hybrid (Small seminar room in the Subaru building and Zoom)
Speaker: Yuhito Shibaike
Affiliation: NAOJ
Title: Constrains on the properties of forming planets from the dust continuum emission of the circumplanetary disks
Abstract:
Although there have been a lot of theoretical research on the formation of gas planets, observational supports have still been very rare. The young T Tauri star PDS 70 has two gas accreting planets sharing one large gap in a pre-transitional disk, which is a valuable system to obtain observational constraints. Recently, dust continuum emission from PDS 70 c has been detected by ALMA Band 7, considered as the evidence of a circumplanetary disk (CPD), a small gas (and dust) disk formed around the planet as a byproduct of the gas accretion. To obtain constraints on the planet properties, we introduce a model of dust evolution in the CPD and reproduce the detection of the dust continuum emission. We find positive correlations between the intensity of the dust emission and three important planet properties, the planet mass, gas accretion rate, and their product called MMdot. We then find that the MMdot of PDS 70 c must be larger than 0.4 MJ^2 /yr, corresponding to the lower limits of the planet mass and the gas accretion rate, 5 MJ and 0.02 MJ/yr. This is the first case to succeed in obtaining constraints on planet properties from the dust continuum emission of a CPD. We also find some loose constraints on the properties of PDS 70 b from the non-detection of its dust emission. We propose possible scenarios for the PDS 70 b and c explaining the non-detection respectively detection of the dust emission from their CPDs. I will also discuss my future plans to obtain constraints on other gas accreting planets if there is enough time.
=============== February 7 Wed===============
Campus: Mitaka
Seminar: NAOJ Science Colloquium
Date and time: 2023 Feb. 7 (Wed.), 15:30-16:30
Place: the large seminar room / Zoom (hybrid)
Speaker: Yui Kawashima
Affiliation: ISAS/JAXA
Title: Subaru/IRD high-resolution spectroscopy of a T-type brown dwarf and investigation of its atmospheric properties with high-resolution spectrum model ExoJAX
Abstract:
While brown dwarf atmospheres share composition and temperature with those of extrasolar gas giant planets, in general, brown dwarfs are observable with a higher signal-to-noise ratio when compared to exoplanets. Thus, the observation of brown dwarf atmospheres helps us establish our understanding of various processes in the atmospheres of such temperature and composition, including chemistry, thermal structure, dynamics, and cloud formation. Also, their high-resolution spectra serve as excellent templates for the observational validation of the molecular line lists at such high temperatures. The accuracy of molecular line lists holds the key to detecting chemical species in exoplanet atmospheres, which are often observed with a lower signal-to-noise ratio.
Recently, we observed the high-resolution spectrum of a T6.5-type brown dwarf Gl 229B with the InfraRed Doppler (IRD) spectrograph mounted on the Subaru Telescope. We have constrained its atmospheric properties, such as the molecular abundances and thermal structure, using an inverse-problem approach with our high-resolution spectrum model ExoJAX (Kawahara, Kawashima et al. 2022). We have also investigated the possibility of inferring the object mass using the embedded information on collision-induced absorption uniquely accessible by high-resolution spectroscopy. Furthermore, we have revealed that in some wavelength regions, specific molecular line lists do not match the observed absorption features.
Facilitator
-Name: Kazumasa Ohno
Comment: English
=============== February 9 Fri==============
Campus： Mitaka
Seminar： Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic： Sporadic
Date and time：9 February (Fri), 10:30-12:00
Place： Zoom
Speaker：Dr. Tetsu Anan
Affiliation：The National Solar Observatory
Title：Measurements of a reconnection electric field in the solar chromosphere
Abstract：The efficient release of magnetic energy in astrophysical plasmas can be achieved through magnetic-field diffusion, the rate of which is directly tied to the associated electric field. However, there have been only a
few attempts to measure electric fields in the solar atmosphere, because of the common assumption that electric fields must vanish quickly or only exist at unresolvable spatial scales. Using the newly commissioned National Science Foundation’s Daniel K. Inouye Solar Telescope (DKIST), we observed NOAA active region 12995 on February 23rd, 2022, in three spectral bands 397 nm, 630 nm, and 854 nm using the Visible SpectroPolarimeter (ViSP). We successfully obtained Stokes spectra of an Ellerman bomb, which is brightening in the lower chromosphere and are thought to be associated with magnetic reconnection. At the Ellerman bomb, we discovered a broadband circular polarization in a Balmer line of the neutral hydrogen at 397 nm, H epsilon, that can only be explained by the presence of an electric field. Moreover, we found that the measured signal filled a region up to ~1000 km, which is three orders of
magnitude larger than that expected in theory. In this talk, we will present our findings and discuss why the diffusion region is so large, and what is the next step.
Facilitator
-Name：Akiko Tei
Comment：English
=============== February 9 Fri==============
Campus：Mitaka
Seminar：NAOJ Seminar
Regularly Scheduled/Sporadic：Regular
Date and time：February 9, 2024 16:00-17:00
Place：Zoom/Large Seminar Room (hybrid)
Speaker：Dr. Eleonora Di Valentino
Affiliation：University of Sheffield
Title：Unresolved Anomalies and Tensions in the Standard Cosmological Model
Abstract: The standard Lambda Cold Dark Matter cosmological model has been incredibly successful in explaining a wide range of observational data, from the cosmic microwave background radiation to the large-scale structure of the universe. However, recent observations have revealed a number of inconsistencies among the model’s key cosmological parameters, which have different levels of statistical significance. These include discrepancies in measurements of the Hubble constant, the S8 tension, and the CMB tension. While some of these inconsistencies could be due to systematic errors, the persistence of such tensions across various probes suggests a potential failure of the canonical LCDM model. I will examine these inconsistencies and discuss possible explanations, including modifications to the standard model, that could potentially alleviate them. However, I will also discuss the limitations of these proposed solutions and note that none of them have successfully resolved the discrepancies.
Facilitator
-Name：Takashi Moriya