2016ApJ...824..136L

We report Shanghai Tian Ma Radio Telescope (TMRT) detections of several long carbon-chain molecules in the C and Ku bands, including HC₃N, HC₅N, HC₇N, HC₉N, C₃S, C₆H, and C₈H toward the starless cloud Serpens South 1a. We detected some transitions (HC₉N J=13-12, F=12-11, and F=14-13; H¹³CCCN J=2-1, F=1-0, and F=1-1; HC¹³CCN J=2-1, F=2-2, F=1-0, and F=1-1; HCC¹³CN J=2-1, F=1-0, and F=1-1) and resolved some hyperfine components (HC₅N J=6-5, F=5-4; H¹³CCCN J=2-1, F=2-1) for the first time in the interstellar medium. The column densities of these carbon-chain molecules in the range 10¹²-10¹³/cm2 are comparable to two carbon-chain molecule rich sources, TMC-1 and Lupu/sA. The abundance ratios are 1.00:(1.11±0.15):(1.47±0.18) for [H¹³CCCN]:[HC¹³CCN]:[HCC¹³CN]. This result implies that the ¹³C isotope is also concentrated in the carbon atom adjacent to the nitrogen atom in HC₃N in Serpens South 1a, which is similar to TMC-1. The [HC₃N]/[H¹³CCCN] ratio of 78±9, the [HC₃N]/[HC¹³CCN] ratio of 70±8, and the [HC₃N]/[HCC¹³CN] ratio of 53±4 are also comparable to those in TMC-1. Serpens South 1a proves to be a suitable testing ground for understanding carbon-chain chemistry.