21
周土星ガス円盤における 単一巨大衛星の形成 藤井悠里 (名古屋大学), 荻原正博 (国立天文台)

satellite Feb2020 Fujii - CPS Web Sitesatellite/2020/pdf/fujii.pdfSatellite Formation •In circumplanetary disks (CPD) –Minimum mass sub-nebula models –Solid enhanced minimum

  • Upload
    others

  • View
    0

  • Download
    0

Embed Size (px)

Citation preview

Page 1: satellite Feb2020 Fujii - CPS Web Sitesatellite/2020/pdf/fujii.pdfSatellite Formation •In circumplanetary disks (CPD) –Minimum mass sub-nebula models –Solid enhanced minimum

周土星ガス円盤における単一巨大衛星の形成

藤井悠里 (名古屋大学), 荻原正博 (国立天文台)

Page 2: satellite Feb2020 Fujii - CPS Web Sitesatellite/2020/pdf/fujii.pdfSatellite Formation •In circumplanetary disks (CPD) –Minimum mass sub-nebula models –Solid enhanced minimum

©NASA

Giant impact

Giant impact or captureCheck out JAXA MMX mission!

Page 3: satellite Feb2020 Fujii - CPS Web Sitesatellite/2020/pdf/fujii.pdfSatellite Formation •In circumplanetary disks (CPD) –Minimum mass sub-nebula models –Solid enhanced minimum

Image taken from A. Crida’s talk

©NASA

©NASA

Check out Charnoz et al. 2010Crida & Charnoz 2012Hyodo et al. 2015

Page 4: satellite Feb2020 Fujii - CPS Web Sitesatellite/2020/pdf/fujii.pdfSatellite Formation •In circumplanetary disks (CPD) –Minimum mass sub-nebula models –Solid enhanced minimum

木星の巨大衛星

ガリレオ衛星:4つ周惑星円盤内で形成

Canup & Ward (2002, 2006)Sasaki et al. (2010)Ogihara & Ida (2012)Miguel & Ida (2016)Fujii et al. (2017)Shibaike et al. (2017, 2019)Cilibrashi et al. (2018)Arakawa & Shibaike (2019)

カリスト

エウロパ

イオ

たくさん研究されている

Page 5: satellite Feb2020 Fujii - CPS Web Sitesatellite/2020/pdf/fujii.pdfSatellite Formation •In circumplanetary disks (CPD) –Minimum mass sub-nebula models –Solid enhanced minimum

Satellite Formation• In circumplanetary disks (CPD)–Minimum mass sub-nebula models

– Solid enhanced minimum mass model

– Gas-starved disk model

– Others (based on simulations)

• From tidally spreading solid disks

e.g. Lunine & Stevenson (1982), Lissauer & Stewart (1993)

Mosqueira & Estrada (2003ab), Miguel & Ida (2016)

Canup & Ward (2002, 2006), Sasaki+ (2010), Ogihara+ (2012)

Fujii+ (2014, 2017), Shibaike+ (2017, 2019), Cilibrasi+ (2018)

Charnoz+ (2010), Crida & Charnoz (2012), Hyodo+ (2016)

Page 6: satellite Feb2020 Fujii - CPS Web Sitesatellite/2020/pdf/fujii.pdfSatellite Formation •In circumplanetary disks (CPD) –Minimum mass sub-nebula models –Solid enhanced minimum

Satellite Formation• In circumplanetary disks (CPD)–Minimum mass sub-nebula models– Solid enhanced minimum mass model

– Gas-starved disk model– Others (based on simulations)

isolated system(learn controlling parameters)

embedded in PPD(learn environments)

Page 7: satellite Feb2020 Fujii - CPS Web Sitesatellite/2020/pdf/fujii.pdfSatellite Formation •In circumplanetary disks (CPD) –Minimum mass sub-nebula models –Solid enhanced minimum

Moon Formation in Gas-starved Disk Canup & Ward (2002, 2006)

前提となる仮定

• Continuous mass infall from PPD

Infall of gas and solids

⇒ Magnetorotational instability is not very efficient(Fujii+ 2011, 2014, Keith+2014, Turner+2014)

Interaction betweendisk and moons

• Turbulent viscosity keeps disk less massive

Page 8: satellite Feb2020 Fujii - CPS Web Sitesatellite/2020/pdf/fujii.pdfSatellite Formation •In circumplanetary disks (CPD) –Minimum mass sub-nebula models –Solid enhanced minimum

衛星の救い方• タイミングよく周惑星円盤が晴れた

• 円盤の内側に穴がある

• 円盤の構造で移動の向きが外向きになる

移動がゆっくりな場合はひとつ救うと後続の衛星も救われる⇒複数の衛星が形成される

Sasaki+ (2010), Ogihara & Ida (2012), Shibaike+ (2017, 2019)

Canup & Ward (2002, 2006)

Fujii+ (2017)

Ogihara & Kobayashi (2013)

Page 9: satellite Feb2020 Fujii - CPS Web Sitesatellite/2020/pdf/fujii.pdfSatellite Formation •In circumplanetary disks (CPD) –Minimum mass sub-nebula models –Solid enhanced minimum

土星の衛星

大きなものはタイタンのみ

土星・木星衛星の作り分けは難しい (cf. Ogihara & Ida 2015)⇒ これまでよりも現実的な円盤モデルを用いて再検討する

大きな衛星を一つだけ形成することは可能かどうか?

Page 10: satellite Feb2020 Fujii - CPS Web Sitesatellite/2020/pdf/fujii.pdfSatellite Formation •In circumplanetary disks (CPD) –Minimum mass sub-nebula models –Solid enhanced minimum

Gas accretion

gas giant

Circumplanetary disk (CPD)

infall

Birth place of moons ALMA (ESO/NAOJ/NRAO) A. Isella; ESO

Protoplanetary Disk (PPD)

Planet formation in PPD

Page 11: satellite Feb2020 Fujii - CPS Web Sitesatellite/2020/pdf/fujii.pdfSatellite Formation •In circumplanetary disks (CPD) –Minimum mass sub-nebula models –Solid enhanced minimum

周惑星円盤の面密度進化

流入項ありの円盤の拡散方程式r :周惑星円盤の半径Σ:面密度ν=αcsH:粘性係数

周惑星円盤

粘性拡散

原始惑星系円盤からの質量流入, f

(Tanigawa+ 2012)

α:粘性パラメータcs:音速H:スケールハイト

f / r�1<latexit sha1_base64="Wsr1lxI/+xIM17RMtSZtslnh8RU=">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</latexit>

Fujii et al. (2014, 2017)と同様

Tanigawa+2012 (Visualization: T. Takeda)

Page 12: satellite Feb2020 Fujii - CPS Web Sitesatellite/2020/pdf/fujii.pdfSatellite Formation •In circumplanetary disks (CPD) –Minimum mass sub-nebula models –Solid enhanced minimum

温度構造の計算

粘性加熱

放射冷却

Tc: 赤道面の温度Te: 有効温度Cp: 定圧比熱vr: r方向の速度κ: オパシティ

(Cannizzo 1993; Armitage+ 2001)

Bell & Lin (1994)

Fujii et al. (2017)と同様

Page 13: satellite Feb2020 Fujii - CPS Web Sitesatellite/2020/pdf/fujii.pdfSatellite Formation •In circumplanetary disks (CPD) –Minimum mass sub-nebula models –Solid enhanced minimum

散逸する円盤の時間進化

面密度 温度

原始惑星系円盤からの流入がなくなると円盤が散逸し始める

〈α=10-4のとき〉時間進化

102

103

104

1 10 100

T [K

]

r [Rp]

initial5x103yr3x104yr1x105yr

10-1

100

101

102

103

104

105

1 10 100

Σ [g

cm

-2]

r [Rp]

initial5x103yr3x104yr1x105yr

定常状態 ⇒ 流入を止めてからの時間進化

Fujii & Ogihara (2020)

Page 14: satellite Feb2020 Fujii - CPS Web Sitesatellite/2020/pdf/fujii.pdfSatellite Formation •In circumplanetary disks (CPD) –Minimum mass sub-nebula models –Solid enhanced minimum

Type I 衛星移動移動タイムスケール

β: 移動の向きを決める係数Mp: 中心惑星の質量 (土星質量)Ms: 衛星の質量 Cs : 音速vK: ケプラー速度

面密度や温度構造の半径依存性で決まる

β>0: 外向きβ<0: 内向き

(e.g., Paardekooper et al. 2011)

Page 15: satellite Feb2020 Fujii - CPS Web Sitesatellite/2020/pdf/fujii.pdfSatellite Formation •In circumplanetary disks (CPD) –Minimum mass sub-nebula models –Solid enhanced minimum

衛星移動の向き5000 year

10 100r [Rp]

0.01

0.1

1

10

Mm

[MTi

tan]

-4

-2

0

2

4

β/(1 + 0.04K) 外向き

内向き

K = (Mm/Mp)2(h/r)−5α−1

(Kanagawa et al. 2015, 2018)

Fujii & Ogihara (2020)

衛星質量[タイタン質量]

Page 16: satellite Feb2020 Fujii - CPS Web Sitesatellite/2020/pdf/fujii.pdfSatellite Formation •In circumplanetary disks (CPD) –Minimum mass sub-nebula models –Solid enhanced minimum

散逸する円盤内での衛星の軌道進化

α=10-3

衛星同士の相互作用なし⇒ ある初期位置においた衛星それぞれの独立した軌道進化

10

100

102 103 104 105

(a)

r [R

p]

Time [year]

移動が外向き

Page 17: satellite Feb2020 Fujii - CPS Web Sitesatellite/2020/pdf/fujii.pdfSatellite Formation •In circumplanetary disks (CPD) –Minimum mass sub-nebula models –Solid enhanced minimum

散逸する円盤内での衛星の軌道進化

α=10-5

衛星同士の相互作用なし⇒ ある初期位置においた衛星それぞれの独立した軌道進化

10

100

102 103 104 105

(c)

r [R

p]

Time [year]

移動が外向き

Page 18: satellite Feb2020 Fujii - CPS Web Sitesatellite/2020/pdf/fujii.pdfSatellite Formation •In circumplanetary disks (CPD) –Minimum mass sub-nebula models –Solid enhanced minimum

散逸する円盤内での衛星の軌道進化

α=10-4

衛星同士の相互作用なし⇒ ある初期位置においた衛星それぞれの独立した軌道進化

10

100

102 103 104 105

(b)

r [R

p]

Time [year]

移動が外向き

Page 19: satellite Feb2020 Fujii - CPS Web Sitesatellite/2020/pdf/fujii.pdfSatellite Formation •In circumplanetary disks (CPD) –Minimum mass sub-nebula models –Solid enhanced minimum

衛星同士の相互作用ありの計算

円盤散逸開始(=ガス流入停止)までに複数の衛星が形成されていたとしても最終的に1つに!

α=10-4

初期条件:0.5MTitan 9個初期条件:1MTitan 7個

100

101

102

102 103 104 105

Sem

imajo

r axis

[Rp]

Time [year]

(b)

100

101

102

102 103 104 105

Sem

imajo

r axis

[Rp]

Time [year]

(a)

Page 20: satellite Feb2020 Fujii - CPS Web Sitesatellite/2020/pdf/fujii.pdfSatellite Formation •In circumplanetary disks (CPD) –Minimum mass sub-nebula models –Solid enhanced minimum
Page 21: satellite Feb2020 Fujii - CPS Web Sitesatellite/2020/pdf/fujii.pdfSatellite Formation •In circumplanetary disks (CPD) –Minimum mass sub-nebula models –Solid enhanced minimum

まとめ• 散逸する周惑星円盤内での衛星の軌道進化を計算• Type I 移動の向き・速度は衛星の質量に依る• 多くのパラメータでは複数 or 0個の衛星形成• タイタン質量の衛星の場合では我々のモデルではα�10-4のときに衛星を1つだけ形成可能

• この結果を足がかりにタイタンの形成について詳しく調べていく必要がある