宇宙電波懇談会シンポジウム2013 “SKA”

星形成・星間媒質研究の視点から
Physics of ISM & Star Formation
Shu-ichiro Inutsuka (Nagoya Univ.)

18 - 19 Dec, 2013

@NAOJ, Mitaka, Tokyo, Japan

Outline• Galactic Structure of Interstellar Medium– Phase Transition  Turbulence– Formation of HI Clouds & Molecular Clouds• Filaments & Star Formation– Star Formation Threshold, Star Formation Rate
– IMF

• High Energy Astrophysics

Galactic Disk in Various Wavelengths
HI 21cm  ISM (T=102-104K)

CO(J=1-0)  Molecular Molecular Clouds (T~10K)

NIR (DIRBE)  mainly K-Giants

X-Ray (ROSAT)  Hot Gas (T=106K)

Various Scale Heights

Galactic Latitude Distribution: n(z)Ionized Gas
HI Gas
H2 GasAverage Number Density 〈n〉 cm-3

Ferrière 2001, Rev.Mod.Phys. 73, 1031

銀河面からの高さ(z)方向の静水圧平衡
種々の重力場モデルに対する静水圧平衡圧力分布の見積もり
Boulares & Cox 1990, ApJ 365, 544

Ferrière 2001, Rev.Mod.Phys. 73, 1031
によるレビュー論文からガス圧

現状では，z方向の（準）静水圧平衡において，ガス圧よりも，磁場圧や宇宙線に起因する圧力が効いていると結論されている． ???

Radial Distribution of Various Energy
NGC6946

assume energy equipartition

M51 Synchrotron

Polarized Intensity(Fletcher & Beck 2005)

シンクロトロン偏波成分の詳細マップ
まだ，理論的説明は無い！

偏光が無い部分がCanal状の構造を作っている．

Waiting for Planck Paper

第１部• 相転移のダイナミックス– 超新星爆発，電離領域膨張– 熱的不安定性乱流– 長さ：Field Length, 時間：Cooling Timescale

Observed “Turbulence” in ISM
Observation of Molecular Clouds
line-width δv > CS
Universal Supersonic Velocity Dispersion
even in the clouds without star formation activity
 should not be due to star formation activity

What is the Origin of “Supersonic Turbulence”
in Molecular Clouds?

Dynamical Timescale of ISM
Dynamical Three Phase Medium–e.g., McKee & Ostriker 1977

 SN Explosion Rate in Galaxy… 1/(100yr)
 Expansion Time…1Myr
2 ×100pc(10kpc) Expansion Radius… 100pc（10-2 yr-1 ）×（106 yr ）×（100pc）3 = 1010 pc3 ∼ VGal.Disk
Dynamical Timescale of ISM ∼ 1Myr

« Timescale of Galactic Density Wave ∼ 100Myr
Expanding HII regions also important
Energetics Argument  SNe

Radiative Equilibrium for a given density
Solid: NH=1019cm-2,

Dashed: 1020cm-2

Warm
MediumCold Neutral
MediumRadiative Cooling & Heating
Solid: Cooling,

Dashed: Heating

158µmgrains

Koyama & SI (2000) ApJ 532, 980 ,(adding CO to Wolfire et al. 1995)

2 Phase in Equilibrium
Solid: NH=1019cm-2,Warm
MediumDashed: 1020cm-2

Saturation
Pressure:
Zeldovich &Pikelner 1969

Cold NeutralMedium

Shock Propagation into WNM
122345Ambient ISM
WNM

Hot Medium

Color: Density
Koyama & Inutsuka (2002) ApJ 564, L97

Summary of TI-Driven Turbulence• 2D/3D Calculation of Propagation of ShockWave into WNM via Thermal Instability
 fragmentation of cold layer into cold
clumps with long-sustained supersonicvelocity dispersion (~ km/s)

κT−2“Field length” :λF ≡10pc→2ρ Λ

1D:Shock ⇒ Eth ⇒ Erad
2D&3D: Shock ⇒ Eth ⇒ Erad + Ekinδv ~ a few km/s < CS,WNM =10km/s
104K due to Lyα line: Universality?
Koyama & SI (2002) ApJ 564, L97

20 pcHennebelle & Audit 07

10,0002
Audit & Hennebelle 2007

3D simulations
12003

Heitsch et al.
40962
2D

Property of 3D"Turbulence"
Muranushi, Inoue & SI 2014 in prep.

14403 Sim
Kolmogorov(αv = 11/3)

δv < CS,WNM
Kolmogorov-likeSpectrum

Good Agreement!

Chepurnov & Lazarian 2010
Armstrong et al. 1995

FAQ
衝撃波が無い場合は，乱流は減衰するか？

答えは NO!

Sustained “Turbulence” in Periodic Box

Periodic Box Evolution without Shock Driving
With Cooling/Heating and Thermal Conduction
Without Physical Viscosity (Prandtl # = 0)

Iwasaki & SI (2013)

磁気雲の形成過程
磁化したWNMを圧縮して分子雲はできるか？
Ref.
Inoue & SI (2008) ApJ 687, 303
Inoue & SI (2009) ApJ 704, 161
Inoue & SI (2012) ApJ 759, 35

Colliding WNM with B0=3µG
v=10km/s
B=3µG(a) 15deg(b) 40 deg

2-Fluid MHD Simulation (AD included)

Colliding WNM with B0=3µG
v=10km/s(a) 15deg<δB2>init = B02(a) 40 deg<δB2>init = 4B02

2-Fluid MHD Simulation (AD included)

Colliding WNM with B0=3µG
v=20km/s(a) 15deg(b) 40 deg

Significant Fraction of Gas in
v=10km/s(c)15deg Thermally Unstable State(d)40
degObservable in HI (Heiles 2001)
v=20km/s(e)<δB2>init = B02(f) <δB2>init = 4B02

分子雲形成の現実的シナリオ
磁化したWNMを圧縮してもHI雲しかできない
Inoue & SI (2008) ApJ 687, 303; Inoue & SI (2009) ApJ 704, 161

HI雲を圧縮する必要がある
multiple episodes of compression.
Converging Flow into 2-Phase Medium
blue: 102/cc < n < 103/cc
magenta: dense clumps n > 103/cc
Inoue & SI (2012) ApJ 759, 35

つまり，分子雲形成は時間がかかる！

Timescales for Phase Transition• Warm Medium
106yr• HI Clouds
107yr?

• Molecular Clouds
105-6yr?

• New-Born Stars
c.f. tMC~20Myr in LMC (Fukui & Kawamura 2010)

HI Clouds vs Molecular Clouds©J. Koda

HI Clouds vs Molecular Clouds

M51 in PAWS Schinnerer+ (2013)

Summary• Shock waves in ISM create

turbulent CNM embedded in WNM.

• TI-driven Turbulence in Multi-Phase ISM– Evaporation/Condensation of CNM clouds– Instabilities in Phase Transition Front– Agree with Observed Kolmogorov Law• Multiple Compressions of Magnetized 2Phase Medium  Molecular Clouds

第２部
Filaments, Filaments, Filaments…
– Star Formation Threshold– Star Formation Rate
– IMF

“The Milky Way in the Herschel Era”
Sep 19-23, 2011@Rome, Italy

Herschel Satellite Telescope found ubiquitous filaments.
ML = ML,crit

AquilaML > ML,crit=2Cs2/Gのフィラメントでは星形成

PolarisRef. André et al. 2010

Character of Self-Gravity of Filaments
Cylindrical Symmetry
1 ∂ ∂Φ
∂ ∂Φ4π G ρ ⇒2 ⋅ 2π G ρ R
R=R=R ∂R ∂R∂R ∂R

Mass perUnitLength

No isothermal pressure support against
collapse  γcrit=1 for cylinder γcrit=4/3 for sphere, γcrit=0 for sheet

Critical Line-Mass for Filaments
Isothermal Equilibrium Filament(Stodolkiewicz 1963; Ostriker 1964)

ρeq(r)∞

2CS2=≈ 2 ×101 M  pc-1
M L,crit ≡ 2π ∫ ρeq (r )rdr
G0If ML < ML,crit , isothermal filament can be pressure-confined.
If ML > ML,crit , isothermal filament collapses indefinitely!
Self-gravity is essential for filament with ML ≈ ML,crit .
(SI & Miyama 1992, 1997)

What is the resultant line-mass?
Fragmentation ofIsothermal Sheet-Like
Cloud

Linear Analysis

λfastest ≈ 4πH = 4Cs2/(GΣ)
 ML ≈ Σλfastest = 4Cs2/G = 2 ML,critNagai, SI, & Miyama 1998

“The Milky Way in the Herschel Era”
Sep 19-23, 2011@Rome, Italy

Herschel Satellite Telescope found ubiquitous filaments.
ML = ML,crit

AquilaML > ML,crit=2Cs2/Gのフィラメントでは星形成

PolarisRef. André et al. 2010

From Ph. André’s Slide @Another Conference

予想外の驚き観測バイアスでは無い(Juvela+2012)

From Ph. André’s SlideWhich is determinant, NH or Filament-Width?

AquilaPolarisHerschel filaments have almost the same radii!
Aquila: 2R=0.1pc & ML = 2Cs2/G  NH ≈ 1022cm-2 (Av= several)
Polaris: 2R=0.1pc & ML < 2Cs2/G  NH < 1022cm-2 (Av< several)“Column Density Threshold” is a consequence?
Onishi+, Lada+, etc.

From Ph. André’s SlideMass Function of Cores in a Filament
SI 2001, ApJ 559, L149

Perturbation of Line-Mass of aFilamentary Cloud using
Press-Schechter Formalism
Power SpectrumP(k) ∝ k –n
Mass Function

Observation of Both Perturbation
SI & Miyama 1997
Spectrum and Mass Function
P (k) ∝ k -1.5
direct test !
t/tff = 0 (dotted) , 2, 4, 6, 8, 10 (solid)
cf. Hennbelle & Chabrier Theory
Observation shows P(k) ~k -1.6 (Andre+2013, PPVI)What is missing?
Formation of Molecular Clouds

Mfilament << Menvelope

Converging Flow into 2-PhaseMediumInoue & SI (2012)

Hα View of Our Galaxy

Wisconsin H-alpha Mapper (WHAM) ; Haffner et al. (2003)

銀河内での中性水素原子の分布

Taurus-Perseus HI Shell
Hartmann & Burton 1997

10

中性水素ガス雲と分子雲
HI=+2.06km/s+02.00km/s
00HIで直径15度の穴が存在。
その周囲にCOガスが分布する。

Galactic Latitude (degrees)+2 km/sの成分-10-10-20-20

Taurus-Perseus HI Shell-30-30190

180

Morino et al.1602002 (NAO) 150

170
Galactic Longitude (degrees)

10

中性水素ガス雲と分子雲
HI=+7.2km/s+7 km/sの成分+07.00km/s

等高線はＣＯの回転遷移輝線のマップ

Galactic Latitude (degrees)

00-10-10-20-20牡牛座分子雲-30-30190

180

170

Morino et al.1602002 (NAO) 150

Ｃ18Ｏの回転遷移輝線のマップ

Column Density Threshold?

Bigiel+2008
AJ 136, 2846

Part 1: Protostellar Collapse Phase
jetOutflow

360 AU
first corev~5 km/s

protostarv~50 km/s

Machida et al. (2006-2009), Banerjee & Pudritz (2006), Hennebelle & Fromang (2008)

Outflows & Jets are Natural By-Products!

Resistive MHD Calc. 分子雲コアから惑星へ

SI, Machida, & Matsumoto (2010) ApJ 718, L58

Global Disk Simulation

Global Calculation
by T. K. Suzuki(2010)

円盤風のz軸方向プロファイル

Distance from Midplane, ZSuzuki & Inutsuka (2009) ApJ 691, L49

惑星形成の最終段階:Disk Dispersal
Disk Windではガスだけが消失する
Suzuki, Muto & SI (2010) ApJ 718 1289

HI輝線はSKA
で見えるか

McJunkin, France+ (2014)arXiv:1312.1650

HII Region in Molecular CloudSh104• study the physical/chemical structure of the shell• Does molecular gas accumulates in the shell shielding FUV photons?

星形成の終焉
周りはHIにIf M* > 20Mo ,then number ofmassive stars
increases
exponetially.
 Star Burst
Hosokawa & SI (2006)
ApJ 648, L131

M* / Mo

第３部• 高エネルギー天体物理との接点– 超新星残骸– 粒子加速M51 Synchrotron

Polarized Intensity(Fletcher & Beck 2005)

Property of 3D"Turbulence"
Muranushi, Inoue & SI 2014 in prep.

14403 Sim
Kolmogorov(αv = 11/3)

δv < CS,WNM
Kolmogorov-likeSpectrum

Good Agreement!

Chepurnov & Lazarian 2010
Armstrong et al. 1995

Mystery: Energy Equipartition?
銀河系の中のエネルギー分布– 銀河系内の（単位体積当り）星起源の輻射場のエネルギーは，Eγ,stellar～ 100 eV/cc

Eγ, 星 ~ Eth, gas ~ E乱流 ~ E宇宙線 ~ E磁場 >~ ECMB「～」の意味は±１桁程度の精度で… 理由は不明？

Overall Equilibrium???

Spectrum of Various Components
Every component has energy density ~ 100 eV/cc .

Eγ, stellar ~ Eth, gas ~ Eturb ~ ECR ~ Emag ~> ECMBA New Type of Quasi-Equilibrium?

Supernova Explosion in Multi-Phase ISM
Shock waves can create turbulence ininhomogeneous pre-shock gas even without
cooling!
Giacalone & Jokipii 2007

tgrowth < tcooling輻射冷却は無視できるSupernova Shock in Multi-Phase ISM
Number Density : n

Magnetic Field Strength : |B|

Warm gas (n ~ 1 cm-3)

B = 6 µG
HI cloud (n ~ 30 cm-3)∇ρ ×∇p ≠ 0： Shock面で渦が発生態（ σv ~ cs ）Shell 内は乱流状∇ρ × ∇p ≠ 0 → Vorticity Creation (δv ~ cs)
Magnetic Field Amplification via Turbulent Dynamo
Bmax ~ 1mG (β ~ 1 @post shock)
Mach # > 104

Inoue, Yamazaki, & SI (2009) ApJ 695, 825

B~mG important for CRs

Inoue, Yamazaki, & SI (2009) ApJ 695, 825; (2010) ApJ 723, L108

X-ray Observations of Supernova@age~103yr
B ~ 1mG (Bamba+2002, Uchiyama+ 2008, etc.)

Crab Nebula in Multi-Phase ISM
Richardson+2013

Summary• Phase Transition Dynamics– Transition Layer Width = λF

– MC Formation Timescale ~107yr?
• Observable as Spiral Structures• Filaments & Star Formation– Star Formation Threshold• Various Environments… Observable– Planet Formation• High Energy Astrophysics– SN Explosion in Multi-Phase ISM– CR acceleration Observable