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Where’s the stuff?
Mass and magnetic distributions in Self-Gravitating Turbulence Simulations with AMR MHD
David Collins UCSD
Wheres the stuff? Mass and magnetic distributions in - - PowerPoint PPT Presentation
Wheres the stuff? Mass and magnetic distributions in - - PowerPoint PPT Presentation
Wheres the stuff? Mass and magnetic distributions in Self-Gravitating Turbulence Simulations with AMR MHD David Collins UCSD A story about power-laws. (Collins, Xu, Norman, Li, Li 2010) (Collins, Padoan, Norman, Xu 2010) AMR, MHD,
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- AMR, MHD, Enzo
- 2048 effective
(Collins, Padoan, Norman, Xu 2010) (Collins, Xu, Norman, Li, Li 2010)
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Supersonic Turbulence
- Dual Role
- Log Normal
Density PDF
- Used to predict
IMF, Star Formation Rate, etc.
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Gravity? Powerlaw
(Collins, Padoan, Norman, Xu 2010) (Kritsuk, Norman, Wagner 2010)
∝ P(ρ) ∝ ρ−1.6
∝
−
Psim(ρ) ∝ ρ−1.5
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Where’s the B?
P(B) ∝ B−2.7
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∝ B ∝ ρ0.5
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ρ ∝ B2 ∝ P(ρ) ∝ ρ−1.5
∝ P(B) ∝ B−3
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“Mass To Flux”
(Troland+2008) (Falgarone+2008)
× − Blos ∝ N0.6
N Blos ∝ M Φ
t=0 t=0.75
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Consistent with Prestellar Cores. ∝ n(M) ∝ M−2.1±0.6
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Ambipolar Diffusion
- I don’t have it.
- Things look pretty good.
- Do I need it?
- When do I need it?
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RAD =
v vAD
∇ × γ χ ρ2 vAD = B2
ℓ
∝ RAD = γ χ ρ2 v ℓ B−2
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∝ RAD = γ χ ρ2 v ℓ B−2
Simulated Chemistry (not simulated: guess)
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= χ ρ
= χ ρ
χ ∝ ρ−1/2
v
- Dynamics>>Recombination
Constant
- Dynamics<<Recombination
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t=0 t=0.75
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RAD = χ ρ2 v ℓ B−2
v
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RAD = χ ρ2 v ℓ B−2
v
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RAD = χ ρ2 v ℓ B−2
v
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Conclusions
- Turbulence + Gravity = Lognormal + Powerlaw
- +Magnetic Fields = Large field strengths+Powerlaw
- AMR + MHD necessary to probe Star Formation
- Excellent agreement with observed “Mass to Flux”
- Excellent agreement with observed mass distribution
- Diffusion maybe unimportant.