Long term evolution of circumstellar discs: DM Tau and GM Aur

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!