2003A&A...398..169K

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 5.15pc² at a distance of 600pc, 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 M_☉, about 6% of the mass traced by C¹⁸O. Six cores are associated with optically invisible IRAS point sources. Their average nonthermal line width is 0.78km/s, while the same quantity for the four starless cores is 0.28km/s. 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 HI obey the line width-size relation Δv_NT∝R_1/2^0.41. 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, <R_1/2≥0.08pc, <T_kin≥13.8K, <Δv_total≥0.64km/s, and <M≥9M_☉ are close to those of the high-mass star forming Perseus and Orion B clouds.