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Thomas Henning and Dima Semenov Chemistry and Dynamics in Protoplanetary Disks Max-Planck-Institut für Astronomie, Heidelberg Courtesy of David E. Trilling.

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Presentation on theme: "Thomas Henning and Dima Semenov Chemistry and Dynamics in Protoplanetary Disks Max-Planck-Institut für Astronomie, Heidelberg Courtesy of David E. Trilling."— Presentation transcript:

1 Thomas Henning and Dima Semenov Chemistry and Dynamics in Protoplanetary Disks Max-Planck-Institut für Astronomie, Heidelberg Courtesy of David E. Trilling

2 Motivation Initial conditions for planet formation Chemical composition of primitive bodies in the solar system Gas depletion and dissipation in disks – Molecules as tracers of disk history Chemistry – Physical state of the disk (temperature, density, radiation, ionization, transport)

3 Any Hot Topics? Coupling between dynamics and chemistry Complete evolutionary track from cold cores to disks (e.g. deuteration sequence) Coupling between solid-phase and gas-phase disk components (grain evolution and settling) Early stellar activity (winds, X-rays, UV, …)

4 Disk Structure ~500 AU100 AU1 AU ~1000 AU 0 Observable region with interferometers wind photon-dominated layer cold midplane warm mol. layer accretion (magneto- rotational instability) hν, UV, X-rays turbulent mixing IS UV, cosmic rays snowline

5 Disk Physics -7 ° - 7 ° (#20) Ω K = 12 Flux limited RT AU (#51) Highly Dynamical Environment Klahr, Henning, and Kley (1999)

6 N. Dziourkevitch & H. Klahr (2006), ApJ, in prep. MRI Overview Rotational axis Magnetic field geometry faster rotation slower rotation centrifugal force & magnetic tension loop generation (turbulence)

7 Ionization Structure of a Disk: Effect of Grain Evolution

8 Semenov, Wiebe, Henning (2004) Layered vertical structure Ionization Structure of a Disk: Effect of Grain Evolution

9 N 2 H + in disks: CID Collaboration (Bordeaux – Heidelberg – Jena – Grenoble - Paris) N 2 H + /HCO + ~ 0.03 HCO + is dominant ion N 2 H + is not a good tracer of ionization Dutrey, Henning et al. (2006), A&A, submitted

10 CID I: N 2 H + in three disks Main results: HCO + remains the more abundant molecular ion in disk [N 2 H + ]/[HCO + ] ~ , similar to dense cores A lower limit on the ionization fraction can be obtained from HCO + column density (and 13 CO abundance) [e] > Comparison observations / model (chemical model by Semenov et al., 2005) Good agreement (even if the slope p Is not yet properly reproduced) ! HCO + and N 2 H +

11 Dynamics and Chemistry Chemically reacting flow system Well-mixed reactor system Flow along predominant direction including mixing

12 Theoretical Milestones Anomalous viscosity (von Weizsäcker, early 40s) α model of disk viscosity (Shakura & Sunyaev 1973) Magneto-rotational instability (Balbus & Hawley 1991) Observational Evidence Non-thermal line broadening (~100 m/s) Crystalline silicates in comets and disks (van Boekel et al. 2005, Crovisier et al. 1997, Wooden et al. 2005) Chondritic refractory inclusions in meteorites (MacPherson et al. 1988) Gas-phase CO at T<25K in DM Tau (Dartois et al. 2003)

13 Observational Evidence Non-thermal line broadening (~100 m/s) Crystalline silicates in comets and disks (van Boekel et al. 2005, Crovisier et al. 1997, Wooden et al. 2005) Chondritic refractory inclusions in meteorites (MacPherson et al. 1988) Gas-phase CO at T<25K in DM Tau (Dartois et al. 2003)

14 Steady Inner Disk Model no vertical mixing vertical mixing CS Ilgner, Henning et al. (2004)

15 Previous Studies Gail & Tscharnuter (>2000): 2D hydro + RT inner disk, gas-phase combustion chemistry, grain evolution crystalline silicate distribution, carbon chains Ilgner et al. (2004; 2006a,b): 1+1D inner disk, 1D vertical mixing & radial transport, gas-grain chemistry molecular abundances Lyons & Young (2005): inner solar nebula, 1D vertical mixing, photochemistry 16/18 oxygen isotopic anomalies Willacy et al. (2006): 1+1D outer disk, 1D vertical chemistry, gas-grain + surface chemistry molecular abundances

16 Chemistry with Dynamics Input: Physical conditions, diffusion coefficient & flow data Initial abundances of species A chemical network A numerical solver Benchmarking Evolution = Formation - Destruction + Diffusion - Advection [ Chemistry ] [ Dynamics ]

17 Surface Chemistry Desorption Accretion Surface reaction (thermal hopping) 2-body reaction UV, CR, X-ray heating Mantle Grain

18 Chemical Network §Updated UMIST95: §Limited deuterium chemistry §Photochemistry: Cosmic rays, UV, X-rays & radioactivity §Accretion & desorption + surface reactions (0.1 μm grains) §Molecular initial abundances §t = a few million years Semenov et al. (2005)

19 Chemistry with Mixing §2D-implicit scheme for chemistry with mixing §Fickian diffusion §Full/reduced chemical networks §1D-benchmarking with K. Willacy & D. Wiebe Semenov, Wiebe, & Henning (2006), ApJL, submitted t ~ N 3 (amount of species in the model)

20 Disk Model §1+1D flared disk (DAlessio et al. 1999) M disk = 0.05M, M dot = M /yr, M = 0.65M, R >10 AU Mixing efficiency D ~ 0.01c s H (Johansen & Klahr 2005) §Radial D = 1.5 x vertical D ~ – cm 2 /g

21 Overview of Mixing Results 10 AU 800 AU

22 Disk Ionization Degree Unaffected by diffusion since chemical equilibrium is reached quickly Comp. Time: 2h 48h 24h >200h Stationary Vertical mix. Radial mix. 2D-Mixing 30x65 grid, 200 species in 1600 reactions 10 AU 800 AU

23 Gas-phase CO at T<25K Abundant CO gas in cold midplane despite fast freeze-out (steep local abundance gradients) Stationary Vertical mix. Radial mix. 2D-Mixing 10 AU 800 AU

24 N(CO) ~ cm -2 (2D-model) optical depth is ~ 1 explains the observations of Dartois et al. (2003) Gas-phase CO at T<25K

25 Gas-phase H 2 CO Diffusion-dependent H 2 CO enrichment due to slow surface processes 100x lower diffusion Stationary Vertical Radial 2D-Mixing 10x lower diffusion 10 AU 800 AU

26 Basic Results Sandwich-like disk structure is preserved Ionization degree is hardly affected Abundance of photo-controlled species are not affected Abundances of more complex (organic) species can be enhanced (grain mantle components, e.g. H 2 CO)

27 Disk Chemistry Large range of temperatures and densities Importance of radiation fields Strong coupling between chemistry and dynamics (ionization, temperature structure, …)

28 Collaborators CID collaboration (A. Dutrey, S. Guilloteau, V. Pietu, A. Bacmann, R. Launhardt, Y. Pavlyuchenko, J. Pety, K. Schreyer, V. Wakelam) D. Wiebe (Moscow): Chemistry with mixing M. Ilgner (London): Chemistry with mixing H. Klahr, A. Johansen (MPIA): Disk dynamics K. Dullemond (MPIA): Grain evolution

29 The End

30 NIR/Mid-IR thermal dust (VLTI: Midi, Amber) Scattered Light in Optical and NIR (opt. thick) mm / submm thermal dust emission (opt. thin) Optically thick CO lines thin lines Domain sampled in current images at 150 pc ~ 500~ 100~ 50~ 1 Vertical scale near the star Approximate radius r (AU) Approximate H(r) at 500 AU (AU) Flaring? Planetesimals?Acc. Rate ~ M /yr Accretion columns (broad emission lines: Hα, etc) Accretion shock Stellar magnetosphere Accretion disk ~ Kuiper Belt Passive reprocessing disk Wind Cumber03.ppt Adapted from A. Dutrey

31 Cumber01.ppt Angular Momentum Machines and Chemical Factories

32 Previous Models Gas and grain chemistry in Bauer et al., 1997 (Non-Equilibrium Thermodynamics) Willacy et al., 1998 Evolution of molecular abundances in proto- planetary disks with accretion flow Aikawa et al., 1999 Simulation of chemical reactions and dust destruction in protoplanetary disks Willacy et al., 2000 The importance of photoprocessing in protoplanetary disks Aikawa et al., 2002 Warm molecular layers in Markwick et al., 2002 Finocchi et al., 1997 Chemical reactions in protoplanetary disks Aikawa et al, 1996 Evolution of molecular abundance in gaseous disks around young stars Molecular distributions in the inner regions of protostellar disks protoplanetary disks

33 accretion rate accretion rate accretion rate Steady Disk Model M / yr yr yr (gas phase and surface chemistry incl. vertical mixing)

34 Steady Disk Model opacity (Henning & Stognienko) opacity (Bell & Lin) yr yr (gas phase and surface chemistry incl. vertical mixing)

35 Chemistry Reduction Code ART Automatic Reduction Technique to reduce sizes of chemical networks: Important species Main destruction and formation reactions Several time steps and disk regions Remove insignificant reactions Final benchmarking Wiebe, Semenov, Henning (2003)

36 Chemical simulations Reduced yet reliable accuracy 5X time gain Surface chemistry >10X loss Old: DVODE + dense matrix formalism slow (1 disk point ~ 5-30 min) Now: DVODPK + sparse matrix formalism fast >200X gain (1 disk point ~1-5 s) t ~ N3!t ~ N3!


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