論文 / 著書情報
Article / Book Information
題目(和文)

埋没惑星によって引き起こされるガスの流れ、ダスト動力学、及び原
始惑星系円盤の構造

Title(English)

Gas flow, dust dynamics, and protoplanetary-disk substructuresinduced by embedded planets

著者(和文)

桑原歩

Author(English)

Ayumu Kuwahara

出典(和文)

学位:博士(理学),学位授与機関:東京工業大学,
報告番号:甲第12323号,
授与年月日:2023年3月26日,
学位の種別:課程博士,審査員:井田 茂,中本 泰史,佐藤 文衛,玄田 英典,奥住 聡

Citation(English)

Degree:Doctor (Science),
Conferring organization: Tokyo Institute of Technology,
Report number:甲第12323号,
Conferred date:2023/3/26,
Degree Type:Course doctor,
Examiner:,,,,

学位種別(和文)博士論文

Category(English)

Doctoral Thesis

種別(和文)

論文要旨

Type(English)

Summary

Powered by T2R2 (Science Tokyo Research Repository)

（博士課程）Doctoral Program論 文 要 旨ＴＨＥＳＩＳ ＳＵＭＭＡＲＹ

系・コース：
Department of, Graduate major in

地球惑星科学
地球惑星科学

学生氏名：
Student’s Name系
コース

桑原歩

申請学位（専攻分野）：

博士

Academic Degree Requested

Doctor of

指導教員（主）：Academic Supervisor(main)（ 桑原歩 ）井田茂

指導教員（副）：Academic Supervisor(sub)要旨（英文 800 語程度）
Thesis Summary （approx.800 English Words ）Planets form in protoplanetary disks. The outcome of planetary growth depends on the environment of disks. The current
observed period-mass distribution of exoplanet suggests the dominance of low-mass planets. Recent high-spatial-resolution
observations have revealed dust substructures in disks such as rings and gaps, which do not always correlate with gas. Theinteraction between the planet and the disk would be a key for interpreting the diversity of exoplanets and observations ofprotoplanetary disks. A growing planet embedded in a disk interacts with the surrounding disk gas and induces three-dimensionalgas flow. Small dust grains are abundant in a disk, and they are sensitive to the gas flow. Planets accrete these small dust grains.
Because gas flow induced by embedded planets could affect dust dynamics, it potentially affects the growth of planets and forms
the observed dust substructures in disks.
In this thesis, we investigate dust dynamics influenced by the planet-induced gas flow and the potential of the planet-induced gas
flow to sculpt the rings and gaps in the dust profiles. Assuming a nonisothermal, inviscid sub-Keplerian gas disk, we first perform
three-dimensional hydrodynamical simulations, which resolve the local gas flow past a planet. We then numerically integrate theequation of motion for dust particles to calculate the trajectories of dust influenced by the planet-induced gas flow. We used theobtained hydrodynamical simulation data to calculate the gas drag force acting on the dust particle. Finally, we compute thesteady-state dust surface density by incorporating the influences of the planet-induced gas flow into a one-dimensional dust
advection-diffusion model.
We find that the gas flow induced by embedded planets affect dust dynamics around planetary orbits and the spatial distributionof dust changes significantly. Throughout this thesis, the key physics is the outflow of the gas. A substantial amount of gas fromthe disk enters the gravitational sphere of the planet (inflow) and exits (outflow). The outflow induced by the embedded planet
occurs in the radial direction to the disk.
The outflow of the gas toward the outside of the planetary orbit inhibits the radial drift of dust, leading to dust accumulation (thedust ring). The outflow toward the inside of the planetary orbit enhances the inward drift of dust, causing dust depletion aroundthe planetary orbit (the dust gap). Under weak turbulence (αdiff≲10-4, whereαdiff is the turbulence strength parameter), the gas flow
induced by the planet with ≳1 M (Earth mass) generates the dust ring and gap in the distribution of small dust grains (≲1 cm)
with a radial extent of ~1̶10 times the gas scale height around the planetary orbit without creating a gas gap and pressure bump.
We find that the response of the spatial distribution of dust to the planet-induced gas flow varies significantly depending on thelocation of the planet within the disk, resulting in the differences in the growth efficiency of planets. The dust gap formation by
the planet-induced gas flow is susceptible to occur in the inner region of the disk (≲1 au), where the growth of the planet via theaccretion of dust onto the planet is suppressed due to the dust gap. The dust ring formation by the planet-induced gas flow issusceptible to occur in the outer region of the disk (≳10 au), where the efficient growth of the planets via dust accretion would beachieved.
Our results suggest that: (1) the gas flow induced by embedded planets can be considered a possible origin of the observed dust
substructures in disks whose dust substructures were found not to correlate with those of the gas, and (2) the planet-induced gas
flow could determine the architecture of planetary systems, which may be helpful in explaining the current observed period-mass
distribution of exoplanets in which the low-mass planets are more frequent than giant planets at <1 au. The dust rings and gaps
formed by the planet-induced gas flow might be probed by future observations using a next-generation Very Large Array (ngVLA)
and a possible future extension to the Atacama Large Millimeter/submillimeter Array (ALMA). Our future work will include morequantitative discussions of both a comparison between our results and ptoroplanetary disk observations using synthetic images
and the influence of the planet-induced gas flow on the planetary growth with additional physics such as dust growth and planet
migration.

備考 : 論文要旨は、和文 2000 字と英文 300 語を 1 部ずつ提出するか、もしくは英文 800 語を 1 部提出してください。
Note : Thesis Summary should be submitted in either a copy of2000 Japanese Characters and 300 Words (Engｌish) or 1copy of 800

Words (English).
注意：論文要旨は、東工大リサーチリポジトリ（T2R2）にてインターネット公表されますので、公表可能な範囲の内容で作成してください。
Attention: Thesis Summary will be published on Tokyo Tech Research Repository

Website (T2R2).