Volume 398, Number 1, January IV 2003
|Page(s)||169 - 180|
|Section||Interstellar and circumstellar matter|
|Published online||14 January 2003|
Probing the structure of a birthplace of intermediate-mass stars: Ammonia cores in Lynds 1340
Konkoly Observatory, 1525 Budapest, PO Box 67, Hungary
2 Joint Astronomy Centre, 660 N. A'ohoku Place, University Park, 96720 Hilo, Hawaii, USA
3 Department of Astronomy, Loránd Eötvös University, 1117 Budapest, Pázmány Péter sétány 1, Hungary
4 Helsinki University Observatory, PO Box 14, 00014 University of Helsinki, Finland
Corresponding author: M. Kun, firstname.lastname@example.org
Accepted: 6 November 2002
Lynds 1340, a molecular cloud forming intermediate-mass stars, has been mapped in the NH3(1,1) and (2,2) transitions with the Effelsberg 100-m telescope. We observed the whole area of the cloud where C18O emission was detected earlier, at a 40″ grid, with additional positions towards the C18O peaks and optically invisible IRAS point sources. Our observations covered an area of 170 arcmin2, corresponding to about 5.15 pc2 at a distance of 600 pc, and revealed 10 ammonia cores. The cores, occupying some 7% of the mapped area, probably represent the highest density regions of L 1340. Their total mass is ~80 , about 6% of the mass traced by C18O. Six cores are associated with optically invisible IRAS point sources. Their average nonthermal line width is 0.78 km s-1, while the same quantity for the four starless cores is 0.28 km s-1. We suggest that the narrow-line cores are destined to form low-mass stars, whereas small groups of intermediate-mass stars are being formed in the turbulent cores. The features traced by NH3, 13CO, C18O and obey the line width–size relation . Comparison of sizes, densities and nonthermal line widths of ammonia cores with those of C18O and 13CO structures supports the scenario in which core formation has been induced by turbulent fragmentation. The typical physical properties of the NH3 cores of L 1340, pc, K, km s-1, and are close to those of the high-mass star forming Perseus and Orion B clouds.
Key words: stars: formation / ISM: molecules / ISM: individual objects: L 1340
© ESO, 2003
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