Studying the chemical and kinematical structures of dense cores TMC-1C, L1544, and TMC-1 in the Taurus molecular cloud using CCS and NH3 observations

Abstract

ABSTRACT The measurement of chemical and kinematic structures in pre-stellar cores is essential for better understanding of the star-formation process. Here, we study three pre-stellar cores (TMC-1C, L1544, and TMC-1) of the Taurus molecular cloud by means of the thioxoethenylidene (CCS) radical and ammonia (NH3) molecule observed with the Karl G. Jansky Very Large Array telescope in the D, C, and CNB configurations. Our main results are based on the CCS observation of the TMC-1C core, showing that complex structures are present. A spatial offset relative to dust emission is observed in the CCS radical. Across a wide region around the dust peak, inward motion is found through the CCS radical. We have calculated the infall velocity and measured the turbulence inside the core. The turbulence is found to be subsonic. We obtain that the virial parameter α is < 1. Thus, thermal and non-thermal motions cannot prevent the collapse. Spatial incoherence of the CCS and NH3 is observed from the integrated intensity maps in these cores, suggesting that these molecules trace different environments in the cores. We compare the integrated flux densities of CCS with previous single-dish data and find that a small amount of flux is recovered in the interferometric observations, indicating the presence of significant diffuse emission in favourable conditions for producing CCS.