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From protostellar cores to disk galaxies - Zurich - 09/2007 S.Walch, A.Burkert, T.Naab Munich University Observatory S.Walch, A.Burkert, T.Naab Munich.

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Presentation on theme: "From protostellar cores to disk galaxies - Zurich - 09/2007 S.Walch, A.Burkert, T.Naab Munich University Observatory S.Walch, A.Burkert, T.Naab Munich."— Presentation transcript:

1 From protostellar cores to disk galaxies - Zurich - 09/2007 S.Walch, A.Burkert, T.Naab Munich University Observatory S.Walch, A.Burkert, T.Naab Munich University Observatory Formation & evolution of protostellar disks around low-mass stars

2 From protostellar cores to disk galaxies - Zurich - 09/2007 Density: Bonnor-Ebert Sphere Central density: max = g/cm³ Temperature: T = 20K Cut-off radius: BE = pc Total mass of the sphere: M BE 5.5M sun EOS: Adiabatic ( =1.4 for H 2 ) + Molecular line cooling: Neufeld et al., (1995) : Mostly H 2, CO, H 2 O, HCl, O 2 Initial Conditions = E therm /E pot 0.1

3 From protostellar cores to disk galaxies - Zurich - 09/2007 Velocity & Angular Momentum: P Thermal line-widths P Velocity gradient maps (e.g. Caselli 2002) Initial Conditions

4 From protostellar cores to disk galaxies - Zurich - 09/2007 Velocity & Angular Momentum: Caused by: Overall core rotation ? From galactic differential rotation; clump-clump collisions? Sub-/Transonic Turbulence? (Burkert & Bodenheimer 2000) Random Gaussian Velocity Fields; P(k) k n, n= Can turbulence account for net rotation? Reproduces Line-Width - Size relationship (Larson 1981): ( ) q (n=-3-2q), q= (e.g. Fuller & Myers 1992) (Kolmogorov: q=0.33, n= - 11 / 3 ) Reproduces projected rotational properties of cores Initial Conditions = E rot /E pot 0.01

5 From protostellar cores to disk galaxies - Zurich - 09/2007 Numerical Issues VINE-Code: VINE-Code: (Wetzstein et al.) MPI-Parallel N-Body + SPH CodeResolution: Particles -> Particle Mass: 1.28·10 -5 M -> Min. resolvable Jeans Mass: 1.28·10 -3 M -> Switch in EOS => M jeans always resolved! Minimum Smoothing Length: Minimum Smoothing Length: hmin = 2AU VINE-Code: VINE-Code: (Wetzstein et al.) MPI-Parallel N-Body + SPH CodeResolution: Particles -> Particle Mass: 1.28·10 -5 M -> Min. resolvable Jeans Mass: 1.28·10 -3 M -> Switch in EOS => M jeans always resolved! Minimum Smoothing Length: Minimum Smoothing Length: hmin = 2AU Boundary Conditions: Periodic in Hydro Isolated in Gravity

6 From protostellar cores to disk galaxies - Zurich - 09/2007 Rigid rotation vs. turbulence Turbulent core: j= cm 2 s -1 Rigidly rotating core: = s -1 => j=10 21 cm 2 s -1

7 From protostellar cores to disk galaxies - Zurich - 09/2007 Rigid rotation vs. turbulence

8 From protostellar cores to disk galaxies - Zurich - 09/2007 Rigid rotation vs. turbulence

9 From protostellar cores to disk galaxies - Zurich - 09/2007 Global core structure z 0.1 pc across

10 From protostellar cores to disk galaxies - Zurich - 09/2007 Global core structure 10 4 AU across z

11 From protostellar cores to disk galaxies - Zurich - 09/2007 Global core structure 2000 AU across z

12 From protostellar cores to disk galaxies - Zurich - 09/2007 Origin of spiral arms?

13 From protostellar cores to disk galaxies - Zurich - 09/2007 SBR: Nice big disks, which grow constantly in size & mass Filamentary & elongated (prolate) global core structure Disk sizes are in agreement with later observations Average Accretion Rates in Class 0 stage: Solid Body: 6.4 ·10 -5 M sun /yr Hb17: 2.3 ·10 -5 M sun /yr With turbulence, irregular infall, accretion is dynamically very complicated: Disks are warped and tilted No Fragmentation: Global gravitational torques cause spiral structure Wide binaries may form due to turbulence in the core - even in Bonnor-Ebert sphere! Conclusions

14 From protostellar cores to disk galaxies - Zurich - 09/2007 Predict observables Predict observables (ALMA, SCUBA, Spitzer) Bridge gap ! When can we first observe young protostars? Parameter study: Parameter study: Fragmentation & Characteristic disk parameters -> Brown Dwarf formation? In core / in disk? -> Gas giant planet formation? Do disks become massive enough? Toomre unstable? Outlook


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