Chemistry in disks. I. Deep search for N2H+ in the protoplanetary disks around LkCa 15, MWC 480, and DM Tauri

Anne Dutrey 1 T. Henning 2 S. Guilloteau 1 D. Semenov 2 V. Piétu 3 K. Schreyer A. Bacmann 1 R. Launhardt 2 J. Pety 3, 4 F. Gueth 3
1 AMOR 2007
L3AB - Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux, OASU - Observatoire aquitain des sciences de l'univers, LAB - Laboratoire d'Astrophysique de Bordeaux [Pessac], Université Sciences et Technologies - Bordeaux 1
Abstract : 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. Methods: We used the IRAM PdBI array to observe the N2H+ J=1-0 line and applied a ?^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. Results: We report two N2H+ detections for LkCa 15 and DM Tau at the 5 ? 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. 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.
Type de document :
Article dans une revue
Astronomy and Astrophysics - A&A, EDP Sciences, 2007, 464, pp.615-623. 〈10.1051/0004-6361:20065385〉
Liste complète des métadonnées

https://hal.archives-ouvertes.fr/hal-00315760
Contributeur : Jérôme Pety <>
Soumis le : vendredi 29 août 2008 - 20:19:58
Dernière modification le : mercredi 19 septembre 2018 - 01:27:15

Lien texte intégral

Identifiants

Collections

Citation

Anne Dutrey, T. Henning, S. Guilloteau, D. Semenov, V. Piétu, et al.. Chemistry in disks. I. Deep search for N2H+ in the protoplanetary disks around LkCa 15, MWC 480, and DM Tauri. Astronomy and Astrophysics - A&A, EDP Sciences, 2007, 464, pp.615-623. 〈10.1051/0004-6361:20065385〉. 〈hal-00315760〉

Partager

Métriques

Consultations de la notice

435