Star-forming regions of the Aquila rift cloud complex - I. NH3 tracers of dense molecular cores

摘要

Aims. The physics of star formation is an important part of Galactic evolution. Most stars are formed in high-density environments (n?>?104 cm-3) and emit lines of diverse molecular transitions. In the present part of our survey we search for ammonia emitters in the Aquila rift complex, which trace the densest regions of molecular clouds. Methods. From a CO survey carried out with the Delingha 14-m telescope we selected ~150 targets for observations in other molecular lines. Here we describe the mapping observations in the NH3(1, 1) and (2, 2) inversion lines of the first 49 sources performed with the Effelsberg 100-m telescope. Results. The NH3(1, 1) emission lines are detected in 12 and the (2, 2) in 7 sources. Among the newly discovered NH3 sources, our sample includes the following well-known clouds: the starless core L694-2, the Serpens cloud cluster B, the Serpens dark cloudL572, the filamentary dark cloud L673, the isolated protostellar source B335, and the complex star-forming region Serpens South. Angular sizes between 40′′ and 80′′ (~0.04–0.08 pc) are observed for compact starless cores but can be as large as 9′ (~0.5 pc) for filamentary dark clouds. The measured kinetic temperatures of the clouds lie between 9 K and 18 K. From NH3 excitation temperatures of 3–8 K we determine H2 densities with typical values of ~?(0.4?4)?×?104 cm-3. The masses of the mapped cores range between ~0.05 and ~?0.5??M⊙. The relative ammonia abundance X?= [NH3]/[H2] varies from 1?×?10-7 to 5?×?10-7 with the mean ??X????=?(2.7?±?0.6)?×?10-7 (estimated from spatially resolved cores assuming a filling factor of η?=?1). In two clouds, we observe kinematically split NH3 profiles separated by ~1 km s-1. The splitting is most likely due to bipolar molecular outflows, for one of which we determine an acceleration of V?? ??0.03 km s-1 yr-1. A starless core with significant rotational energy is found to have a higher kinetic temperature than the other ones, which is probably caused by magnetic energy dissipation.