Chemical and physical small-scale structure in a pre-stellar core
Institut für integrierte Naturwissenschaften, Abteilung Physik, Universität Koblenz-Landau, Universitätsstr. 1, 56070 Koblenz, Germany e-mail: email@example.com
2 Radioastronomisches Institut, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany e-mail: firstname.lastname@example.org
3 Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany e-mail: email@example.com
Accepted: 9 June 2008
Aims. We present a comparative study of several molecular lines and of the dust contiunuum at 1.2mm in a pre-stellar core that is embedded in the Galactic cirrus cloud MCLD123.5+24.9. Previous studies found that the core is gravitationally stable and shows signs of inward motion.
Methods. Using the Owens Valley (OVRO) and Plateau de Bure (PdB) interferometers we obtained high-angular resolution maps of the core in the carbon monosulfide CS (21) and the cyanoacetylene HC3N (109) transitions. Together with CS (54), C34S (32), and bolometer data obtained with the IRAM 30 m telescope, we analyse the excitation conditions and the structural properties of the cloud.
Results. On the one hand, the new CS (J = 21) observations reveal significant substructure on a scale of about , i.e., the beam size, corresponding to about 1050 AU at an adopted distance of 150 pc. On the other hand, the interferometric observations in the HC3N (J = 109) transition shows just one single well resolved clump in the inner part of the core. This core is well described by an intensity profile following from a centrally peaked volume density distribution. We find no evidence for depletion of CS onto dust grains. The inward motion seen in the CS (21) occurs one-sided from the middle of the filamentary cloud towards the HC3N core.
Key words: ISM: clouds / ISM: abundances / ISM: molecules / stars: formation
© ESO, 2008