Ringberg1 The gas temperature in T- Tauri disks in a 1+1-D model Bastiaan Jonkheid Frank Faas Gerd-Jan van Zadelhoff Ewine van Dishoeck Leiden observatory

Ringberg2 Why T gas ? Critical for understanding disk’s structure and dynamics. Critical for understanding disk’s structure and dynamics. T gas determines line emission. T gas determines line emission. Difficulties: Difficulties: Optically thick disk (see Kamp & van Zadelhoff for optically thin disks). Optically thick disk (see Kamp & van Zadelhoff for optically thin disks). Full 2-D radiative transfer is too slow. Full 2-D radiative transfer is too slow.  adopt a 1+1-D formulation.  adopt a 1+1-D formulation.

Ringberg3 Physical processes in the thermal balance Heating rates include: Heating rates include: Photoelectric heating on PAHs and large grains Photoelectric heating on PAHs and large grains Cosmic ray heating Cosmic ray heating Heating through formation, dissociation and deexcitation of H 2 Heating through formation, dissociation and deexcitation of H 2 Cooling rates include: Cooling rates include: [O I], [C II] and [C I] fine structure lines [O I], [C II] and [C I] fine structure lines CO rotational lines CO rotational lines Gas-dust collisions Gas-dust collisions

Ringberg4 1+1-D formalism (1) Advantages: Advantages: Simple 1-D radiative transfer Simple 1-D radiative transfer Gives correct results in optically thin and thick limits Gives correct results in optically thin and thick limits Detailed treatment of H 2 and CO photodissociation Detailed treatment of H 2 and CO photodissociation Disadvantages: Disadvantages: Overestimate UV intensity Overestimate UV intensity Uncertain results in intermediate regions Uncertain results in intermediate regions

Ringberg5 1+1-D formalism (2) Use 1-D code for photon dominated regions (tested for benchmark cases) to model each vertical slice Use 1-D code for photon dominated regions (tested for benchmark cases) to model each vertical slice Use densities and dust temperatures of D’Alessio et al (1999) (α=0.01, dM/dt=10 -8 Use densities and dust temperatures of D’Alessio et al (1999) (α=0.01, dM/dt=10 -8 M  yr -1 ). Use UV intensities at the surface by van Zadelhoff et al. (2003) (  105 AU wrt Draine field) Use UV intensities at the surface by van Zadelhoff et al. (2003) (  105 AU wrt Draine field) The code calculates gas-phase chemistry and temperature. The code calculates gas-phase chemistry and temperature.

Ringberg6 Dust settling Settling of large grains is simulated by varying the gas/dust ratio. Settling of large grains is simulated by varying the gas/dust ratio. Small particles (PAHs) stay well mixed. Small particles (PAHs) stay well mixed. PAHs are assumed to absorb ~50% of the UV radiation. PAHs are assumed to absorb ~50% of the UV radiation.

Ringberg7 Effects on chemistry

Ringberg8 Effects on the temperature (1): a vertical slice

Ringberg9 Effects on heating

Ringberg10 Effects on the temperature (2): 2-D distribution

Ringberg11 Effects on the temperature (3) distribution over mass

Ringberg12 Effects on emission lines

Ringberg13 Conclusions T gas » T dust in the optically thin part of the disk. T gas » T dust in the optically thin part of the disk. The intensity of high energy emission lines is increased dramatically. The intensity of high energy emission lines is increased dramatically. Dust settling increases the amount of warm gas in the disk, but has only limited influence on the chemistry in the current formulation. Dust settling increases the amount of warm gas in the disk, but has only limited influence on the chemistry in the current formulation.

Ringberg14 Future work 2-D radiative transfer for the UV radiation. 2-D radiative transfer for the UV radiation. 2-D escape probability formalism for cooling radiation. 2-D escape probability formalism for cooling radiation. Investigate the influence of X-rays on the thermal balance. Investigate the influence of X-rays on the thermal balance. Apply models to a real disk: HD Apply models to a real disk: HD