HAL : hal-00019201, version 1

arXiv : astro-ph/0602396

DOI : 10.1051/0004-6361:200600005

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Astronomy and Astrophysics 448/2 (2006) L5-L8

Deuterated molecules in DM Tau: DCO+, but no HDO

S. Guilloteau 1, 2, 3, 4, Vincent Piétu 5, Anne Dutrey 1, 2, 3, 4, Michel Guélin 5

(2006)

We report the detection of the J=2-1 line of DCO+ in the proto-planetary disk of DM Tau and re-analyze the spectrum covering the 465 GHz transition of HDO in this source, recently published by Ceccarelli et al. (2005). A modelling of the DCO+ line profile with the source parameters derived from high resolution HCO+ observations yields a DCO+/HCO+ abundance ratio of about 0.004, an order of magnitude smaller than that derived in the low mass cores. The re-analysis of the 465 GHz spectrum, using the proper continuum flux (0.5 Jy) and source systemic velocity (6.05 km/s), makes it clear that the absorption features attributed to HDO and C6H are almost certainly unrelated to these species. We show that the line-to-continuum ratio of an absorption line in front of a Keplerian disk can hardly exceed the ratio of the turbulent velocity to the projected rotation velocity at the disk edge, unless the line is optically very thick (tau > 10 000). This ratio is typically 0.1-0.3 in proto-planetary disks and is about 0.15 in DM Tau, much smaller than that for the alleged absorption features. We also show that the detection of H2D+ in DM Tau, previously reported by these authors, is only a 2-sigma detection when the proper velocity is adopted. So far, DCO+ is thus the only deuterated molecule clearly detected in proto-planetary disks.

1 :	Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB)
	CNRS : UMR5804 – INSU – Université Sciences et Technologies - Bordeaux I
2 :	Laboratoire d'Astrophysique de Bordeaux (LAB)
	CNRS : UMR5804 – INSU – Université Sciences et Technologies - Bordeaux I
3 :	Observatoire aquitain des sciences de l'univers (OASU)
	CNRS : UMS2567 – INSU – Université Sciences et Technologies - Bordeaux I
4 :	Université Sciences et Technologies - Bordeaux 1
	Université Sciences et Technologies - Bordeaux I
5 :	Institut de RadioAstronomie Millimétrique (IRAM)
	CNRS : UPS2074

Équipe de recherche : RADIOASTRONOMIE 2006

Domaine

:

Physique/Astrophysique/Cosmologie et astrophysique extra-galactique Planète et Univers/Astrophysique/Cosmologie et astrophysique extra-galactique Planète et Univers/Astrophysique

Mots Clés : Stars: circumstellar matter – planetary systems: protoplanetary disks – individual: DM Tau – Radio-lines: stars

hal-00019201, version 1

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Contributeur : Vincent Piétu <>

Soumis le : Vendredi 17 Février 2006, 14:39:13

Dernière modification le : Lundi 12 Décembre 2011, 10:36:03