Constraining TW Hydra Disk Properties Chunhua Qi Harvard-Smithsonian Center for Astrophysics Collaborators : D.J. Wilner, P.T.P. Ho, T.L. Bourke, N. Calvet (CfA) G.A. Blake(Caltech), M. Hogerheijde(Leiden), N. Ohashi(ASIAA), E. Bergin (U. Michigan)

TW Hya disk in scattered light  Closest classical T Tauri star, 56 pc in distance  Nearly face on disk around.  Strong X-ray, UV radiation  Age variable from Myr, highly evolved system Weinberger et al. 2002

Outline  SMA observations  Dust continuum emission ( GHz)  Molecular line emission (cool gas K)  2D radiative transfer calculation and Chi- square analysis on disk properties  Temperature profile (surface heating)  Outer radius  Vsini at 100 AU  Depletion  Summary

SMA Observations

TW Hya Continuum The SMA continuum measurements agree well with the predictions of the physically self-consistent irradiated accretion disk model for TW Hya (Calvet et al. 2002) The SMA continuum measurements agree well with the predictions of the physically self-consistent irradiated accretion disk model for TW Hya (Calvet et al. 2002) The radial brightness distribution of the disk observed at 345 GHz is also consistent with the Calvet model. The radial brightness distribution of the disk observed at 345 GHz is also consistent with the Calvet model.

TW Hya Images I CO 2-1 CO CO 2-1

TW Hya Images II HCN 3-2 HCO CN 2-1

(Sub)mm molecular emission typically from cool gas k (Sub)mm molecular emission typically from cool gas k Some common lines are optically thick like CO Some common lines are optically thick like CO Physical and chemical processes ( freeze out, photodissociation etc.) add the complexity of analysis. Physical and chemical processes ( freeze out, photodissociation etc.) add the complexity of analysis. Aikawa et al Van Zadelhoff et al. 2003

Data Analysis We use a 2-D accelerated Monte Carlo model (Hogerheijde & van der Tak 2000) to calculate the radiative transfer and molecular excitation. We use a 2-D accelerated Monte Carlo model (Hogerheijde & van der Tak 2000) to calculate the radiative transfer and molecular excitation. Chi-square analysis Chi-square analysis Chi-square contour

Blue: Canonical Model (Calvet et al. 2002, Qi et al ) Black: SMA data CO 2-1CO 3-2 Temperature Contour Tau=1 Surfaces CO 3-2 CO 2-1

The Effects of X-Rays The heating by X-rays The heating by X-rays The dust-gas cooling The dust-gas cooling Glassgold & Najita 2001 Mean heating energy per ionization Mean dust radius

Blue: Canonical Model (Calvet et al. 2002, Qi et al ) Black: SMA data Red: Model with X ray heating CO 2-1 CO 6-5 CO 3-2

Constaining Outer Radius R out 172 ± 2 AU R out 172 ± 2 AU Vsini at 100 AU 0.27± 0.01km/s Vsini at 100 AU 0.27± 0.01km/s Turbulence velocity 0.12 ± 0.01 km/s Turbulence velocity 0.12 ± 0.01 km/s Uncertainty can be limited by the velocity resolution. Uncertainty can be limited by the velocity resolution. CO

Smaller outer radius: photochemical effect ? 13 CO R out 110 ± 5 AU R out 110 ± 5 AU Isotope-selective photodissociation of CO Isotope-selective photodissociation of CO HCN R out 120 ± 10 AU R out 120 ± 10 AU HCN large cross sections which absorb Lyα radiation HCN large cross sections which absorb Lyα radiation CO/ 13 CO=60

13 CO 2-1 Data Model (R out 110 AU) Model (R out 172 AU)

Depletion Dc: constant depletion factor Dc: constant depletion factor Dj: jump depletion factor where the kinetic temperature falls below 22K Dj: jump depletion factor where the kinetic temperature falls below 22K Dc: Dj: Dc: Dj:

Summary Dust emission follows closely the predictions of the irradiated accretion disk model of Calvet et al Dust emission follows closely the predictions of the irradiated accretion disk model of Calvet et al Higher gas temperature vs dust temperature on the disk surface is needed to explain the line intensity, probably due to X-ray heating. Higher gas temperature vs dust temperature on the disk surface is needed to explain the line intensity, probably due to X-ray heating. Outer radius can be well constrained, given the resolution small enough. We have the first clear evidence of the isotope-selective photodissociation of CO in the disk. Outer radius can be well constrained, given the resolution small enough. We have the first clear evidence of the isotope-selective photodissociation of CO in the disk. Substantial CO depletion, by an order of magnitude or more, is required to explain the line emission. Substantial CO depletion, by an order of magnitude or more, is required to explain the line emission.

Constraining inclination We can resolve the disk at radii where most of the disk mass resides. Can place strong constraints on vsini at 100AU. We can resolve the disk at radii where most of the disk mass resides. Can place strong constraints on vsini at 100AU. Very hard to use the kinematics to disentangle M from inclination. Better spectral resolution is needed. Very hard to use the kinematics to disentangle M from inclination. Better spectral resolution is needed. (Vsini)=0.27 km/s

CO 2-1 Data Model vsini (i=6 o ) Model vsini=0.273, (i=13.5 o )