Deuterium fractionation in the Horsehead edge - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Astronomy and Astrophysics - A&A Année : 2007

Deuterium fractionation in the Horsehead edge

Résumé

Context: Deuterium fractionation is known to enhance the [ DCO^+] /[ HCO^+] abundance ratio over the D/H ? 10-5 elemental ratio in the cold and dense gas typically found in pre-stellar cores. Aims: We report the first detection and mapping of very bright DCO^+J=3-2 and J=2-1 lines (3 and 4 K respectively) towards the Horsehead photodissociation region (PDR) observed with the IRAM-30m telescope. The DCO+ emission peaks close to the illuminated warm edge of the nebula (<50'' or ~0.1 pc away). Methods: Detailed nonlocal, non-LTE excitation and radiative transfer analyses have been used to determine the prevailing physical conditions and to estimate the DCO+ and H13CO+ abundances from their line intensities. Results: A large [ DCO^+] /[ HCO^+] abundance ratio (?0.02) is inferred at the DCO+ emission peak, a condensation shielded from the illuminating far-UV radiation field where the gas must be cold (10-20 K) and dense (? 2 × 105 cm-3). DCO+ is not detected in the warmer photodissociation front, implying a lower [ DCO^+] /[ HCO^+] ratio (<10-3). Conclusions: .According to our gas phase chemical predictions, such a high deuterium fractionation of HCO+ can only be explained if the gas temperature is below 20 K, in good agreement with DCO+ excitation calculations. Based on observations obtained with the IRAM Plateau de Bure interferometer and 30?m telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).

Dates et versions

hal-00126363 , version 1 (24-01-2007)

Identifiants

Citer

J. Pety, J. R. Goicoechea, Pierre Hily-Blant, M. Gerin, D. Teyssier. Deuterium fractionation in the Horsehead edge. Astronomy and Astrophysics - A&A, 2007, 464, pp.L41-L44. ⟨10.1051/0004-6361:20067009⟩. ⟨hal-00126363⟩
56 Consultations
0 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More