Thomas Henning and Dima Semenov

Chemistry and Dynamics in Protoplanetary Disks

Max-Planck-Institut für Astronomie, Heidelberg

Courtesy of David E. Trilling

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)

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, …)

Disk Structure

~500 AU100 AU1 AU

~1000 AU

0

Observable region with interferometers

wind

photon-dominated layer

cold midplanewarm mol. layer

accretion (magneto-rotational instability)

hν, UV, X-rays

turbulent mixing

IS UV, cosmic rays

snowline

Disk Physics

-7 ° - 7 ° (#20)ΩK = 12

Flux limited RT

3.5 - 6.5 AU (#51)

Highly Dynamical Environment

Klahr, Henning, and Kley (1999)

N. Dziourkevitch & H. Klahr (2006), ApJ, in prep.

MRI OverviewR

otat

iona

l axi

s

Mag

neti

c fi

eld

geom

etry

faster rotation slower rotation

centrifugal force & magnetic tension loop generation(turbulence)

Ionization Structure of a Disk: Effect of Grain Evolution

Semenov, Wiebe, Henning (2004)

„Layered“ vertical structure

Ionization Structure of a Disk: Effect of Grain Evolution

N2H+ in disks: CID Collaboration (Bordeaux – Heidelberg – Jena – Grenoble - Paris)

N2H+/HCO+ ~ 0.03

HCO+ is dominant ionN2H+ is not a good

tracer of ionization

Dutrey, Henning et al. (2006), A&A, submitted

10

1010

1012

Dynamics and Chemistry

Chemically reacting flow system

„Well-mixed reactor system“

Flow along predominant direction including mixing

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)

Steady Inner Disk Model

no vertical mixing vertical mixing

CS CS

Ilgner, Henning et al. (2004)

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

Chemistry with Dynamics

Input: Physical conditions, diffusion coefficient & flow data

Initial abundances of species A chemical network A numerical solver Benchmarking

iil

lliikj

kjjki UnnnDnnknnnk

t

n

H2H2

,

/

Evolution = Formation - Destruction + Diffusion - Advection [ Chemistry ] [ Dynamics ]

Chemistry with Mixing

2D-implicit scheme for chemistry with mixing Fickian diffusion Full/reduced chemical networks1D-benchmarking with K. Willacy & D. Wiebe

Semenov , Wiebe, & Henning (2006), ApJL, submitted

t ~ N3 (amount of species in the model)

Disk Model

1+1D flared disk (D‘Alessio et al. 1999) Mdisk= 0.05M, Mdot = 10-8M/yr, M = 0.65M, R >10 AU

Mixing efficiency D ~ 0.01csH (Johansen & Klahr 2005)

Radial D = 1.5 x vertical D ~ 1015 – 1018 cm2/g

Overview of Mixing Results

10 AU 800 AU

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 reactions10 AU 800 AU

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

N(CO) ~ 1017 cm-2 (2D-model) optical depth is ~ 1 explains the observations of Dartois et al. (2003)

Gas-phase CO at T<25K

Gas-phase H2CO

Diffusion-dependent H2CO enrichment due to slow surface processes

100x lower diffusion

Stationary Vertical Radial 2D-Mixing

10x lower diffusion

10 AU 800 AU

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.

H2CO)

Disk Chemistry

Large range of temperatures and densities

Importance of radiation fields

Strong coupling between chemistry and dynamics (ionization, temperature structure, …)

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

The End