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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 358760.0, MPI für Astronomie / Publikationen_mpia
Chemistry in disks. I. Deep search for N2H+ in the protoplanetary disks around LkCa 15, MWC 480, and DM Tauri
Authors:Dutrey, A.; Henning, T.; Guilloteau, S.; Semenov, D.; Piétu, V.; Schreyer, K.; Bacmann, A.; Launhardt, R.; Pety, J.; Gueth, F.
Date of Publication (YYYY-MM-DD):2007
Title of Journal:Astronomy and Astrophysics
Start Page:615
End Page:623
Audience:Not Specified
Abstract / Description:Aims.To constrain the ionization fraction in protoplanetary disks, we present new high-sensitivity interferometric observations of N2H+ in three disks surrounding DM Tau, LkCa 15, and MWC 480.<BR /> Methods: .We used the IRAM PdBI array to observe the N2H+ J=1-0 line and applied a chi^2-minimization technique to estimate corresponding column densities. These values are compared, together with HCO+ column densities, to results of a steady-state disk model with a vertical temperature gradient coupled to gas-grain chemistry.<BR /> Results: .We report two N2H+ detections for LkCa 15 and DM Tau at the 5 sigma level and an upper limit for MWC 480. The column density derived from the data for LkCa 15 is much lower than previously reported. The [ N2H^+/HCO^+] ratio is on the order of 0.02-0.03. So far, HCO+ remains the most abundant observed molecular ion in disks.<BR /> Conclusions: .All the observed values generally agree with the modelled column densities of disks at an evolutionary stage of a few million years (within the uncertainty limits), but the radial distribution of the molecules is not reproduced well. The low inferred concentration of N2H+ in three disks around low-mass and intermediate-mass young stars implies that this ion is not a sensitive tracer of the overall disk ionization fraction. Based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain). Research partially supported by PCMI, the French national program for the Physics and Chemistry of the Interstellar Medium.
Free Keywords:stars: pre-main sequence; planetary systems: protoplanetary disks; submillimeter
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie

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