Survey Observations to Study Chemical Evolution from High-Mass Starless
  Cores to High-Mass Protostellar Objects II. HC$_{3}$N and N$_{2}$H$^{+}$
  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.
