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A&A 419, L35-L38 (2004)
DOI: 10.1051/0004-6361:20040140

Letter

Disappearance of N $\mathsf$ from the gas phase in the class 0 protostar IRAM 04191

A. Belloche1, 2 and P. André3

1  Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
2  LERMA/LRA, École Normale Supérieure, 24 rue Lhomond, 75231 Paris Cedex 05, France
3  Service d'Astrophysique, CEA/DSM/DAPNIA, C.E. Saclay, 91191 Gif-sur-Yvette Cedex, France
    e-mail: pandre@cea.fr

(Received 23 February 2004 / Accepted 10 April 2004 )

Abstract
We present a high-resolution millimeter study of the very young class 0 protostar IRAM 04191+1522 in the Taurus molecular cloud. N 2H +(1-0) observations with the IRAM Plateau de Bure Interferometer and 30 m telescope demonstrate that the molecular ion N 2H + disappears from the gas phase in the inner part of the protostellar envelope ( r < 1600 AU, $n_{\mbox{\tiny }} > 5 \times 10^5$ cm -3). This result departs from the predictions of current chemical models. It suggests either that N 2 is more depleted than the models predict, owing to a higher binding energy on polar ice or an enhanced grain chemistry transforming N 2 to less volatile species, or that strong deuterium fractionation enhances N 2D + to the detriment of N 2H +.


Key words: stars: formation -- circumstellar matter -- stars: individual: IRAM 04191+1522 -- ISM: abundances -- astrochemistry -- stars: rotation

Offprint request: A. Belloche, belloche@mpifr-bonn.mpg.de

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