Title: Long%20term%20evolution%20of%20circumstellar%20discs:%20DM%20Tau%20and%20GM%20Aur
1Long term evolution of circumstellar discs DM
Tau and GM Aur
- Ricardo Hueso () Tristan Guillot
- Laboratoire Cassini, Observatoire de la Côte
dAzur, Nice, France - () Now at E.T.S. Ing. Ind. y Telecom. UPV,
Bilbao, Spain
Circumstellar disks protoplanets, Nice,
February 2003
2Initial 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?
- Is it viscous evolution the most important factor
determining disk properties on the long term?
- Different models of turbulence
- a prescription , b prescription,
- Shear, convection, MRI, surface MRI, waves
- Statistics about protoplanetary disks begin to be
available. - Life-span, disk masses, star accretion
- rates with time
Make simple models of disk formation evolution
and compare with available observations. Set up
model parameters and test turbulence
prescriptions.
Circumstellar disks protoplanets, Nice,
February 2003
3Models of Disk Formation and Evolution
Fast 1D models
Including gravitational collapse of rotating
isothermal spheres
Viscous evolution source terms
Simplified radiative transfer
Additional equations for disk properties
Photoevaporation (Long term simulations)
Circumstellar disks protoplanets, Nice,
February 2003
4Two models of turbulence a and b
- na r 3/4 nb r ½ ?
- Are finally both parameterizations so different
when applied?
Circumstellar disks protoplanets, Nice,
February 2003
5Observational characteristics of DM Tau and GM Aur
Circumstellar disks protoplanets, Nice,
February 2003
6Comparing model with DM Tau
PAREMETERS
a 0.005 wcd 3 10-14 s-1 Tcd 10 K M0 0.3 M?
Circumstellar disks protoplanets, Nice,
February 2003
7Comparing model with DM Tau
PAREMETERS
Circumstellar disks protoplanets, Nice,
February 2003
8Comparing model with DM Tau
Circumstellar disks protoplanets, Nice,
February 2003
9Constraining model parameters
Selecting models
All Models
Circumstellar disks protoplanets, Nice,
February 2003
10Constraining model parameters
Selecting models
All Models CO Star age mass
Circumstellar disks protoplanets, Nice,
February 2003
11Constraining model parameters
Selecting models
All Models CO Star age mass CO Dust
Circumstellar disks protoplanets, Nice,
February 2003
12Constraining model parameters
Selecting models
All Models CO Star age mass CO Dust CO
Dust Accretion Rate
Circumstellar disks protoplanets, Nice,
February 2003
13Constraining model parameters
Selecting models
All Models CO Star age mass CO Dust CO
Dust Accretion Rate
Circumstellar disks protoplanets, Nice,
February 2003
14Set of model parameters fitting the observational
constraints
- Practically a standard accretion disk.
Circumstellar disks protoplanets, Nice,
February 2003
15Set of model parameters fitting the observational
constraints
- Greater Temperature (15 K)
- (Faster early formation)
- Less dispersion with Temperature
Circumstellar disks protoplanets, Nice,
February 2003
16a vs. b DM Tau GM Aur
Knowing the data for the disk within an order of
5 doesnt improve these plots. Iincertitudes come
also from the assumed star age and its mass.
Circumstellar disks protoplanets, Nice,
February 2003
17Conclusions
- 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!
Circumstellar disks protoplanets, Nice,
February 2003