Chemical characterization of the first stages of protoplanetary disk formation Collaborators : Valentine Wakelam (supervisor) Stéphane Guilloteau (supervisor) Franck Hersant Astrochemistry of Molecules and ORigins of planetary systems (AMOR) Laboratoire d’Astrophysique de Bordeaux, France Ugo Hincelin – 25th June 2010

Is there a link between interstellar matter & disk matter? Introduction Method Results Prospects Disk formation Is there a link between interstellar matter & disk matter? Are initial conditions of disk formation important for the disk chemical composition? Is thermal history of disk formation important?

<-- initial chemical composition of a diffuse cloud Introduction Method Results Prospects Modelling steps Steps: simulate chemistry during different phases (diffuse cloud  molecular cloud  disk) How? using chemical gas-grain model Nautilus (Hersant et al. 2009, based on Herbst’s team) <-- initial chemical composition of a diffuse cloud T = 10K n = 2.104 cm-3 different ages --> final chemical composition of molecular cloud = initial conditions for disk formation T = f(time) nH = f(time) different evolution scenarios --> chemical composition of the disk

density & temperature profiles Introduction Method Results Prospects density & temperature profiles Scenarios, from molecular cloud collapse to disk, extracted from hydrodynamic models (Visser et al. 2009…) gas cell trajectory arrival at 30AU from the protostar at 2.5x105 yr R (AU) z (AU) (Visser et al. 2009) temperature and density along trajectory = parameters for Nautilus

3 models : testing the initial conditions Introduction Method Results Prospects list of models List of models used 3 models : testing the initial conditions 1 trajectory  evolution of T & n different initial conditions for disk formation : varying the age of the molecular cloud 104 105 106 years old 2 models : testing the evolution ‘s impact of the temperature and the density molecular cloud : 105 years old 1) 1 trajectory  evolution of T & n 2) no evolution of T & n 5 models : testing changes in thermal and density history molecular cloud : 106 years old temperature of the accretion shock (100K & 780K) time of the shock (early & late) temperature decreasing after the accretion shock

testing the initial conditions Introduction Method Results Prospects testing the initial conditions  Dependence of the disk chemical composition on initial conditions (age of parent cloud) About one order of magnitude difference in the abundances of a lot of species when varying initial conditions  Final chemical composition of the disk is influenced by the age of the parent cloud Chemistry is not at equilibrium  time = important factor H2CO = tracer of the age of the parent cloud? Temperature and density evolution from Visser’s trajectory

testing the initial conditions – comparison with comets composition Introduction Method Results Prospects testing the initial conditions – comparison with comets composition - Similar abundances for some species (C2H2, H2CO…) - Little CO on grain : disk temperature too high - Lot of CO2 in 1 case : OH + CO  CO2 + H (efficient reaction) (Bockelée-Morvan et al. 2004)

testing thermal and density history Introduction Method Results Prospects testing thermal and density history testing thermal and density history ------ model with evolution for T & n (Visser’s trajectory) model without evolution for T & n  thermal and density history of gas and dust changes the final chemical composition of the disk

testing changes in thermal and density history Introduction Method Results Prospects testing changes in thermal and density history parametric functions for the temperature and density profiles maximal density Shock temperature final temperature Time of the transition time of the shock minimal density

CO abundance reproduced Introduction Method Results Prospects testing changes in thermal and density history – temperature decreased at the end of the disk formation use of Visser’s temperature profile with final decrease – cloud of 106yr CO abundance reproduced Results closer to comets composition (13/17 abundances reproduced within 1 order of magnitude)

 HCOOCH3, a tracer of temperature of the shock? Introduction Method Results Prospects testing changes in thermal and density history – temperature of the shock parametric functions – cloud of 106yr  No big changes except for some species  good for identification of tracers  HCOOCH3, a tracer of temperature of the shock?

testing changes in thermal and density history – time of the shock Introduction Method Results Prospects testing changes in thermal and density history – time of the shock parametric functions – cloud of 106yr  Again no big changes except for some species  good for identification of tracers  HC3N and C2H2, tracers of the shock of the time?

Test other trajectories and link parametric profiles with trajectories Introduction Method Results Prospects Conclusion : Chemical composition of the disk is sensitive to the density and thermal history Some tracers would give us some information about the thermal history of the disk Chemical composition of comets seems to be a melting pot of matter from different locations in the disk (and envelope?)… Prospects : Test variation on the temperature peak width  ongoing work Add a high temperature network in chemical model to better simulate warm regions Test other trajectories and link parametric profiles with trajectories

Thank you for your attention Introduction Method Results Prospects Conclusion : Chemical composition of the disk is sensitive to the density and thermal history Some tracers would give us some information about the thermal history of the disk Chemical composition of comets seems to be a melting pot of matter from different locations in the disk (and envelope?)… Prospects : Test variation on the temperature peak width  ongoing work Add a high temperature network in chemical model to better simulate warm regions Test other trajectories and link parametric profiles with trajectories Thank you for your attention