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# 2022.05.09-2022.05.15

キャンパス：三鷹
セミナー名：太陽系小天体セミナー

名前：渡部潤一

## 5月10日（火）

Campus: Mitaka
Seminar: SOKENDAI Doctoral Thesis Preliminary Defense 総研大博士学位論文予備審査会
Date and time: May 10, 2022, 10:00～
Place: Zoom
Speaker1
10:00～10:40　　Yongming Liang
Title1：Correlation between Galaxies and IGM at z≈2 Mapped by Subaru/HSC
Speaker2
11:00～11:40　　Nao Fukagawa
Title2：Chemical Evolution of Dwarf Galaxies
Facilitator
-Name：Hideyuki Kobayashi, Yumiko Omura (Graduate Student Affairs Unit)
-URL：https://guas-astronomy.jp/CampusLife/doctor_report_pre.html

## 5月11日（水）

Campus：Mitaka
Seminar：SOKENDAI Colloquium
Date and time：May 11th , 2022 10:30-12:00
Place：Zoom
Speaker 1：Ryota Ikeda
Affiliation：SOKENDAI 2nd year (M2) (Supervisor: Daisuke Iono, Ken-ichi Tadaki, Masayuki Tanaka)
Title：The Mystery of [CII] Halo
Speaker 2：Ko Hosokawa
Affiliation：SOKENDAI 4th year (D2) (Supervisor: Takayuki Kotani, Yosuke Minowa, Yuka Fujii)
Title：Detectability of Atmospheric molecules from Directly Imaged Exoplanet by obtaining high-resolution spectra

Facilitator

## 5月11日（水）

Campus：Mitaka
Seminar：NAOJ Science Colloquium
Date and time：2022/5/11, 15:30-17:00
Place：zoom
Speaker：Kangrou Guo
Affiliation：NAOJ (D3)
Title：Planetesimal dynamics in the presence of a giant planet II – the dependence of outer planetesimal orbits on planet mass and eccentricity
Abstract：The presence of an existing planet embedded in the protoplanetary disk has mixed influence on the growth of other planetary embryos. Gravitational perturbation from the planet can increase the relative velocities of planetesimals at the mean motion resonances to very high values and impede accretion at those locations. However, it can also align the orbital pericenters of planetesimals in certain regions of the disk and thus make them dynamically quiet and “accretion-friendly” locations for planetary growth. Following the previous paper, where we investigated the effect of a Jupiter-like planet on an external planetesimal disk, we generalize our findings to extrasolar planetary systems by varying the planet parameters. In particular, we focus on the dependence of the planetesimal relative velocities on the mass and eccentricity of the existing planet. We found that the velocity dispersion of identical-mass particles increases monotonically with increasing planet mass. Meanwhile, the dependence of the relative velocity between different-mass planetesimals on their mass ratio becomes weaker as the planet mass increases. While the relative velocity generally increases with increasing planet eccentricity, the velocity dispersion of smaller-mass particles ($m \lesssim 10^{18}~\rm{g}$) is almost independent of planet eccentricity owing to their strong coupling to the nebula gas. The results suggest that in a protoplanetary disk with a massive planet ($\gtrsim M_{\rm{Jup}}$) in presence, subsequent planet formation can be challenging. Our results could provide some clues for the formation of Saturn’s core and the orbital features of extrasolar cold giant planets.

Speaker: Fei Wang
Affiliation：NAOJ (D3)
Title：Unveiling non-gray surface of cloudy exoplanets: the influence of wavelength-dependent surface albedo and cloud scattering properties on retrieval solutions
Abstract：Direct-imaging spectra hold rich information about a planet’s atmosphere and surface, and several space-based missions aiming at such observations will become a reality in the near future. Previous spectral retrieval works have resulted in key atmospheric constraints under the assumption of a gray surface, but the effect of wavelength-dependent surface albedo on retrieval has not been shown. We explore the influence of the coupling effect of cloud and wavelength-dependent surface albedo on retrieval performance via modeling suites of Earth-like atmospheres with varying cloud and surface albedo parameterizations. Under the assumption of known cloud scattering properties, the surface spectral albedos can be reasonably recovered when the surface cover represents that of Earth-like vegetation or ocean, which may aid in characterizing the planet’s habitability. When the cloud scattering properties cannot be assumed, we show that the degeneracy between the cloud properties and wavelength-dependent surface albedo leads to biased results of atmospheric and cloud properties. The multi-epoch visible band observations offer limited improvement in disentangling this degeneracy. However, the constraints on atmospheric properties from the combination of UV band (R ~ 6) + visible band (R = 140) are consistent with input values to within 1σ. If short bandpass data is not available, an alternative solution to reduce the retrieval uncertainties would be to have the prior constraints on planetary cloud fraction with less than 20% uncertainty.

Facilitator
-Name：Akimasa Kataoka

Home > その他 | 太陽系小天体セミナー | 科学研究部コロキウム | 総研大コロキウム > 2022.05.09-2022.05.15