users meeting abe · 2020-01-23 · upper limit of filament mass fraction and sfe (inutsuka et al....

$: users meeting ABE · 2020-01-23 · Upper Limit of Filament mass fraction and SFE (Inutsuka et al. 2015) Massive stars with quench the star formationM > 20 M stars can be created,$
分子雲中におけるフィラメント形成と星形成効率 Filament Mass Fraction & Star Formation Efficiency in molecular cloudsDaisei Abe Collaborator : Tsuyoshi Inoue, Shuichiro Inutsuka

Nagoya University Laboratory of Theoretical Astronomy & Astrophysics (TA-lab.)

“Filament Paradigm”

Filament formation in molecular clouds -> Gravitational Collapse of Filaments -> Star Formation (SF)

Gravitational Collapse of Filaments determines the initial condition of star formation

Herschel discovered the universality of filamentary structures in molecular clouds

1

0.1

Unstable M

line /Mline,crit3

pc

log NH2map (cm−2)

21 22

Herschel Aquila filaments(André et al. . 2010)

: proto star: core

ユーザーズミーティング 1/15・16 @NAOJ

A Candidate of Filament Formation

B

Dense Clump in Cloud

Shock

vz

1

Collapse -> Star Formation

4

2

vzShock

B

Filament Formation

3

BShock

Colu

mn

dens

ityB0 lo

g[N

H2(

cm−

2 )]

BGas flow

y [pc]

z [pc

]

Filament formation can be explained by shock compression of molecular clumps(Inoue & Fukui 2013)

−3.0Inoue et al. 2018

3.0

−3.

03.

0

21.6

23.0

CCC etc.ex.)


Motivation of Our Study


-> How much fraction of shocked gas is converted into the dense filamentary gas?

-> Inoue & Fukui mechanism requires shock compression for dense filament creation. (Inoue & Fukui 2013)

Lada et al. 2010

Total mass of the clouds

Mass of dense gas component with > Av8 mag

~10—20%

Observation of Mass Fraction

Average star formation efficiency (SFE) of galaxies ~ a few %

Dens Gas Fraction

= NH2 ≃ 1.5 × 1022 cm−2

Simulation Setup

Numerical simulation by SFUMATO code (Matsumoto 2007)

-> Creation of dense gas layer

Turbulence velocity dispersion:Δv = 1.0 km/s

B0 = 10 μG

Conversing Flow of Molecular Gas

• Self Gravity• Ideal MHD• Isothermal• Resolution : 0.012 pc• 512 CPU-cores

y

6.0

[pc]

z [pc]

6.0

BFast Shock

Fast Shock

x [pc]

Gas Flow

Gas Flow


6.0

6.0

6.0

6.0

0.00.0

0.00.0 y [pc]

y [pc]

z [pc]

x [pc]

B

B

Simulation Setup

-> analyze filament mass fraction ( > Av8 mag) & SFE

Simulations by various parameters

Star : Sink particleFilament : Regions with Av > 8 mag.(= )

Definitions


y [pc]

z [pc] vz nH2

B vz

• Gas Flow Velocity ; 1 km/s, 2 km/s • Magnetic Field Strength ; 10 μG, 5.5 μG • Magnetic Field Orientation ; 90°( ), 45°( ) • Initial Density ; 300 cm-3, 1000 cm-3

vzB

nH2

NH2 ≃ 1.5 × 1022 cm−2

Upper Limit of Filament mass fraction and SFE

(Inutsuka et al. 2015)M > 20 M⊙Massive stars with quench the star formation

stars can be created,

200M⊙

20M⊙

Expansion Timescale

TlagTlag =

2 3RSt

7CHII ( 3 [pc]RSt )

7/4

− 13 pc

RIF : Ionization FrontRSt : Str··omgren Radius

CHII : Sound Speed in HII region

Chabrier IMF

Stellar Mass [M⊙]St

ella

rN

umbe

rdN

/dM

120 M⊙

total 200 M⊙if total stellar mass exceeds

RIF = RSt (1 +74

43

CHIItRSt )

4/7(Hosokawa & Inutsuka 2006)


How to evaluate mass fraction

Time [Myr]

2,00

04,

000

6,00

020

0

Mas

s[M

⊙]y

6.0

[pc]

z [pc]

6.0

Shock

Shock

Gas Flow

Gas Flow

Shocked Gas Mass


Total Stellar MassNH2 ≥ 1.5 × 1022 cm−2

Time [Myr]

2,00

04,

000

6,00

020

0

Mas

s[M

⊙]y

6.0

[pc]

z [pc]

6.0

Shock

Shock

Gas Flow

Gas Flow

Shocked Gas Mass




Time [Myr]

2,00

04,

000

6,00

020

0

Mas

s[M

⊙]y

6.0

[pc]

z [pc]

6.0

Shock

Shock

Gas Flow

Gas Flow

Snap Shot @1.0Myr

y [pc

]

6.0x [pc]

6.0

0.00.0 21

22

Colu

mn

dens

itylo

g[N

H2(

cm−

2 )]

Shocked Gas Mass




Time [Myr]

2,00

04,

000

6,00

020

0

Mas

s[M

⊙]y

6.0

[pc]

z [pc]

6.0

Shock

Shock

Gas Flow

Gas Flow

Snap Shot @1.0Myr

y [pc

]

6.0x [pc]

6.0

0.00.0 21

22

Colu

mn

dens

itylo

g[N

H2(

cm−

2 )]

more than 20 M⊙Star Formation

Shocked Gas Mass




Time [Myr]

2,00

04,

000

6,00

020

0

Tlag = 0.44 [Myr]

Mas

s[M

⊙]y

6.0

[pc]

z [pc]

6.0

Shock

Shock

Gas Flow

Gas Flow

Snap Shot @1.0Myr

y [pc

]

6.0x [pc]

6.0

0.00.0 21

22

Colu

mn

dens

itylo

g[N

H2(

cm−

2 )]

more than 20 M⊙Star Formation

Shocked Gas Mass




Results 1/4 : Dependence on Collision Velocity

Time [Myr]Time [Myr]

Ms = 6.7Ms

Fast Collision Slow Collision

FMF ∼ 10 %

SFE ∼ 4 %

FMF ∼ 12 %

SFE ∼ 5 %Mas

sFr

actio

n[%

]

Mas

sFr

actio

n[%

]

B = 10 μGnH2 = 300 cm−3

y

6.0

[pc]

z [pc]

6.0

vz

vz

nH2

B

(vz = 1 km/s)


0.5 1.5.0 .0.0

aNH2 ≥ 1.5 × 1022 cm−2

Ms = 13.3: Mach number(vz = 2 km/s)

FMF : filament mass fraction

Fraction(FMF)

Results 2/4 : Dependence on Magnetic Field Strength


Strong B Weak BB = 10 μG B = 5.5 μG

FMF ∼ 9 %SFE ∼ 5 %M

ass

Frac

tion

[%]

Mas

sFr

actio

n[%

]

nH2 = 300 cm−3

y

6.0

[pc]

z [pc]

6.0

vz

vz

nH2

B

vz = 2.0 km/s


aNH2 ≥ 1.5 × 1022 cm−2

FMF ∼ 10 %

SFE ∼ 4 %


Fraction(FMF)

Results 3/4 : Dependence on Magnetic Field Orientation


Mas

sFr

actio

n[%

]

Mas

sFr

actio

n[%

]FMF ∼ 14 %

SFE ∼ 5 %

=45°

y

z Gas Flow

Gas Flow

θ

B = 10 μGnH2 = 300 cm−3

y

6.0

[pc]

z [pc]

6.0

vz

vz

nH2

B

vz = 2.0 km/s


aNH2 ≥ 1.5 × 1022 cm−2

FMF ∼ 10 %

SFE ∼ 4 %


θ=90°

Fraction(FMF)

Results 4/4 : Dependence on Initial Density


SFE ∼ 4 %Mas

sFr

actio

n[%

]

Mas

sFr

actio

n[%

]

B = 10 μGy

6.0

[pc]

z [pc]

6.0

vz

vz

nH2

B

nH2 = 300 cm−3

vz = 2.0 km/s


aNH2 ≥ 1.5 × 1022 cm−2

FMF ∼ 10 %

SFE ∼ 4 %

FMF ∼ 22 %

nH2 = 1,000 cm−3


Fraction(FMF)

Summary


• Simulation results => Filament Mass Fraction ~ 10%, SFE ~ a few %

Consistent with observations

• New Paradigm of Star Formation = “Filament Paradigm”

• Can Inoue-Fukui mechanism creates dense filamentary gas whose mass fraction is consistent with observations?

• Carried out 3D isothermal MHD simulations

users meeting abe · 2020-01-23 · upper limit of filament mass fraction and sfe (inutsuka et al....

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