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Long term evolution of circumstellar discs: Long term evolution of circumstellar discs: DM Tau and GM AurDM Tau and GM Aur
Ricardo Hueso (*) & Tristan Guillot
Laboratoire Cassini, Observatoire de la Côte d’Azur, Nice, France(*) Now at: E.T.S. Ing. Ind. y Telecom. UPV, Bilbao, Spain
Circumstellar disks & protoplanets, Nice, February 2003
Initial questions:Initial questions:
• Are models of star & disk formation able to compare with observations and give constraints on relevant disk physics?
• Numerous Parameterizations.How to set up values for the most relevant parameters?
Circumstellar disks & protoplanets, Nice, February 2003
• Is it viscous evolution the most important factor determining disk properties on the long term?
• Different models of turbulence prescription , prescription,Shear, convection, MRI, surface MRI, waves
• Statistics about protoplanetary disks begin to be available.
Life-span, disk masses, star accretion
rates with time …
• This work:
Make simple models of disk formation & evolution and compare with available observations. Set up model parameters and test turbulence prescriptions.
Models of Disk Formation and EvolutionModels of Disk Formation and Evolution
Circumstellar disks & protoplanets, Nice, February 2003
PAREMETERS
Tcloud
cloud
Mcloud
Several long term simulationsof DM Tau and GM Aur
Compare with observations
Fast 1D modelsFast 1D models
Including gravitational collapse of rotating isothermal spheres:
cteM
+Additional equations for disk properties
+Simplified radiative transfer
+Photoevaporation (Long term simulations)
Viscous evolution + source terms
Two “models” of turbulence: Two “models” of turbulence: and and
Non-Linear shear instability
ddRR3
Non-Linear shear instability
ddRR3
Not easy to study in numerical experiments!!
Intensity from experiments inrotating tanks.
~ 2 x 10-5
Not easy to study in numerical experiments!!
Intensity from experiments inrotating tanks.
~ 2 x 10-5
HCs
Mixing-Length
csH ~ r 3/4
Mixing-Length
csH ~ r 3/4
Only a parameterization!
Models of MRI ~ 0.01 - 0.1Used also when considering others kind of mechanisms for the turbulence
Only a parameterization!
Models of MRI ~ 0.01 - 0.1Used also when considering others kind of mechanisms for the turbulence
~ r 3/4~ r ½
Are finally both parameterizations so different when applied?
~ r 3/4~ r ½
Are finally both parameterizations so different when applied?
Circumstellar disks & protoplanets, Nice, February 2003
Observational characteristics of DM Tau and GM AurObservational characteristics of DM Tau and GM Aur
Guilloteau & Dutrey, 1998Simon, Guilloteau & Dutrey, 2001
CO Maps of disk emission:Temperature and retrievals
Dust Maps of diffused light: RetrievalsKitamura et al. 2002
Spectral Energy Dist. (IR) Signatures of Star accretion RateHartmann et al. 1998
Circumstellar disks & protoplanets, Nice, February 2003
Comparing model with DM TauComparing model with DM Tau
= 0.005cd = 3 10-14 s-1
Tcd = 10 KM0 = 0.3 M
PAREMETERS
Circumstellar disks & protoplanets, Nice, February 2003
Comparing model with DM TauComparing model with DM Tau
= 0.005cd = 3 10-14 s-1
Tcd = 10 KM0 = 0.3 M
PAREMETERS
Circumstellar disks & protoplanets, Nice, February 2003
Comparing model with DM TauComparing model with DM Tau
= 0.005cd = 3 10-14 s-1
Tcd = 10 KM0 = 0.3 M
PAREMETERS
csH
ddRR3
csH
ddRR3
Explore parameter space.
Test parameterizations of turbulence
Explore parameter space.
Test parameterizations of turbulence
Circumstellar disks & protoplanets, Nice, February 2003
Constraining model parametersConstraining model parameters::
All Models
Circumstellar disks & protoplanets, Nice, February 2003
Selecting modelsSelecting models
All Models
CO + Star age & mass
Circumstellar disks & protoplanets, Nice, February 2003
Constraining model parametersConstraining model parameters::
Selecting modelsSelecting models
All Models
CO + Star age & mass
CO + Dust
Circumstellar disks & protoplanets, Nice, February 2003
Constraining model parametersConstraining model parameters::
Selecting modelsSelecting models
All Models
CO + Star age & mass
CO + Dust
CO + Dust + Accretion Rate
Circumstellar disks & protoplanets, Nice, February 2003
Constraining model parametersConstraining model parameters::
Selecting modelsSelecting models
All Models
CO + Star age & mass
CO + Dust
CO + Dust + Accretion Rate
Circumstellar disks & protoplanets, Nice, February 2003
Constraining model parametersConstraining model parameters::
Selecting modelsSelecting models
Set of model parameters fitting the Set of model parameters fitting the observational constraints:observational constraints:
Circumstellar disks & protoplanets, Nice, February 2003
Practically a standard accretion disk.
Set of model parameters fitting the Set of model parameters fitting the observational constraints:observational constraints:
More mass is needed Less Turbulence Greater Temperature (15 K) (Faster early formation)
Less dispersion with Temperature
Circumstellar disks & protoplanets, Nice, February 2003
vs. vs. : DM Tau & GM Aur: DM Tau & GM Aur
models behave globally like models
models show bigger dispersion in turbulence
They have almost
unchanged in time while models evolve from high turbulence to less turbulent stages.
Circumstellar disks & protoplanets, Nice, February 2003
Knowing the data for the disk within an order of 5 doesn’t improve these plots.Iincertitudes come also from the assumed star age and its mass.
ConclusionsConclusions
Circumstellar disks & protoplanets, Nice, February 2003
• Models of purely viscous discs are able to explain presently observed characteristics of circumstellar disks like DM Tau and GM Aur. We can obtain valuable information about the relevant parameters governing disk formation and evolution.• Large incertitudes on the determination of physical properties.
Results depends on assumptions such as CO depletion or dust abundance.
Incertitudes give rise to one-two orders of magnitude indetermination of disk viscosity.
• Alpha an Beta parameterizations of turbulence work equally well (or bad)
to fit the observations.• GM Aur requires 10 times less turbulence than DM Tau. Consequence of a more massive disk combined with a lower accretion rate.
Why? Simply more massive system, older, or ...A procative posibility. Can this reduced “accretion” be interpreted in terms of an internal gap in GM Aur? SED of GM Aur seems to suggest a gap!