From protostellar cores to disk galaxies - Zurich - 09/2007

S.Walch, A.Burkert, T.NaabS.Walch, A.Burkert, T.Naab

Munich University Munich University ObservatoryObservatory

S.Walch, A.Burkert, T.NaabS.Walch, A.Burkert, T.Naab

Munich University Munich University ObservatoryObservatory

Formation & evolution Formation & evolution of protostellar disksof protostellar disksaround low-mass starsaround low-mass stars

Formation & evolution Formation & evolution of protostellar disksof protostellar disksaround low-mass starsaround low-mass stars

From protostellar cores to disk galaxies - Zurich - 09/2007

Density: Bonnor-Ebert SphereCentral density: max =10-18 g/cm³

Temperature: T = 20K

Cut-off radius: BE= 6.9 0.1pc

Total mass of the sphere: MBE 5.5Msun

EOS: Adiabatic ( =1.4 for H2)+ Molecular line cooling: Neufeld et al., (1995): Mostly H2, CO, H2O, HCl, O2

Initial Conditions

= Etherm/Epot

0.1

From protostellar cores to disk galaxies - Zurich - 09/2007

Velocity & Angular Momentum:Thermal line-widthsVelocity gradient maps (e.g. Caselli

2002)

Initial Conditions

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) kn , n=-3..-4 Can turbulence account for net rotation?Reproduces Line-Width - Size relationship (Larson 1981):

() q (n=-3-2q), q=0.25..0.75 (e.g. Fuller & Myers 1992)

(Kolmogorov: q=0.33, n= - 11/3)Reproduces projected rotational properties of cores

Initial Conditions

= Erot/Epot

0.01

From protostellar cores to disk galaxies - Zurich - 09/2007

Numerical IssuesVINE-Code: VINE-Code: (Wetzstein et al.)

MPI-Parallel N-Body + SPH Code

Resolution:Resolution:430 000 Particles

-> Particle Mass: 1.28·10-5M

-> Min. resolvable Jeans Mass: 1.28·10-3M

-> Switch in EOS => Mjeans always resolved!

Minimum Smoothing Length:Minimum Smoothing Length: hmin = 2AU

VINE-Code: VINE-Code: (Wetzstein et al.)

MPI-Parallel N-Body + SPH Code

Resolution:Resolution:430 000 Particles

-> Particle Mass: 1.28·10-5M

-> Min. resolvable Jeans Mass: 1.28·10-3M

-> Switch in EOS => Mjeans always resolved!

Minimum Smoothing Length:Minimum Smoothing Length: hmin = 2AU

Boundary Conditions: Periodic in Hydro Isolated in Gravity

From protostellar cores to disk galaxies - Zurich - 09/2007

Rigid rotation vs. turbulence

Turbulent core: j=2.7•1021 cm2s-1

Rigidly rotating core: =6•10-14 s-1 => j=1021 cm2s-1

From protostellar cores to disk galaxies - Zurich - 09/2007

Rigid rotation vs. turbulence

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benötigt.

Zur Anzeige wird der QuickTime™ Dekompressor „YUV420 codec“

benötigt.

From protostellar cores to disk galaxies - Zurich - 09/2007

Rigid rotation vs. turbulence

From protostellar cores to disk galaxies - Zurich - 09/2007

Global core structure

z

0.1 pc across

From protostellar cores to disk galaxies - Zurich - 09/2007

Global core structure

104 AU across

z

From protostellar cores to disk galaxies - Zurich - 09/2007

Global core structure

2000 AU across

z

From protostellar cores to disk galaxies - Zurich - 09/2007

Origin of spiral arms?

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 Msun/yr Hb17: 2.3 ·10-5 Msun/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

From protostellar cores to disk galaxies - Zurich - 09/2007

Predict observablesPredict 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