Letter to the Editor

CN in prestellar cores

¹ IRAM, Domaine Universitaire, 300 rue de la Piscine, 38406 Saint-Martin d'Hères, France e-mail: hilyblan@iram.fr
² INAF – Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy
³ IAS (UMR 8617 du CNRS), Université de Paris-Sud, 91405 Orsay, France
⁴ LERMA (UMR 8112 du CNRS), Observatoire de Paris, 61 avenue de l'Observatoire, 75014 Paris, France
⁵ Physics Department, The University, Durham DH1 3LE, UK

Received: 20 December 2007
Accepted: 15 January 2008

Abstract

Context.Determining the structure of and the velocity field in prestellar cores is essential to understanding protostellar evolution.

Aims.We have observed the dense prestellar cores L 1544 and L 183 in the N = 1 0 rotational transition of CN and ¹³CN in order to test whether CN is depleted in the high-density nuclei of these cores.

Methods.We have used the IRAM 30 m telescope to observe along the major and minor axes of these cores. We compare these observations with the 1 mm dust emission, which serves as a proxy for the hydrogen column density.

Results.We find that while CN(1-0) is optically thick, the distribution of ¹³CN(1-0) intensity follows the dust emission well, implying that the CN abundance does not vary greatly with density. We derive an abundance ratio of [CN]/[ H₂] = 10^-9 in L 183 and   10^-9 in L 1544, which, in the case of L 183, is similar to previous estimates obtained by sampling lower-density regions of the core.

Conclusions.We conclude that CN is not depleted towards the high-density peaks of these cores and thus behaves like the N-containing molecules N₂H and NH₃. CN is, to our knowledge, the first C-containing molecule to exhibit this characteristic.