http://arxiv.org/abs/1901.06446
We have carried out survey observations of molecular emission lines from HC${3}$N, N${2}$H$^{+}$, CCS, and cyclic-C${3}$H${2}$ in the 81$-$94 GHz band toward 17 high-mass starless cores (HMSCs) and 28 high-mass protostellar objects (HMPOs) with the Nobeyama 45-m radio telescope. We have detected N${2}$H$^{+}$ in all of the target sources except one and HC${3}$N in 14 HMSCs and in 26 HMPOs. We investigate the $N$(N${2}$H$^{+}$)/$N$(HC${3}$N) column density ratio as a chemical evolutionary indicator of massive cores. Using the Kolmogorov-Smirnov (K-S) test and Welch’s t test, we confirm that the $N$(N${2}$H$^{+}$)/$N$(HC${3}$N) ratio decreases from HMSCs to HMPOs. This tendency in high-mass star-forming regions is opposite to that in low-mass star-forming regions. Furthermore, we found that the detection rates of carbon-chain species (HC${3}$N, HC${5}$N, and CCS) in HMPOs are different from those in low-mass protostars. The detection rates of cyanopolyynes (HC${3}$N and HC${5}$N) are higher and that of CCS is lower in high-mass protostars, compared to low-mass protostars. We discuss a possible interpretation for these differences.
K. Taniguchi, M. Saito, T. Sridharan, et. al.
Wed, 23 Jan 19
111/111
Comments: Accepted for publication in The Astrophysical Journal, 29 pages, 16 figures, 8 tables