Astrochemical Properties of Planck Cold Clumps
  We observed thirteen Planck cold clumps with the James Clerk Maxwell
Telescope/SCUBA-2 and with the Nobeyama 45 m radio telescope. The N$_2$H$^+$
distribution obtained with the Nobeyama telescope is quite similar to SCUBA-2
dust distribution. The 82 GHz HC$_3$N, 82 GHz CCS, and 94 GHz CCS emission are
often distributed differently with respect to the N$_2$H$^+$ emission. The CCS
emission, which is known to be abundant in starless molecular cloud cores, is
often very clumpy in the observed targets. We made deep single-pointing
observations in DNC, HN$^{13}$C, N$_2$D$^+$, cyclic-C$_3$H$_2$ toward nine
clumps. The detection rate of N$_2$D$^+$ is 50\%. Furthermore, we observed the
NH$_3$ emission toward 15 Planck cold clumps to estimate the kinetic
temperature, and confirmed that most of targets are cold ($\lesssim$ 20 K). In
two of the starless clumps observe, the CCS emission is distributed as it
surrounds the N$_2$H$^+$ core (chemically evolved gas), which resembles the
case of L1544, a prestellar core showing collapse. In addition, we detected
both DNC and N$_2$D$^+$. These two clumps are most likely on the verge of star
formation. We introduce the Chemical Evolution Factor (CEF) for starless cores
to describe the chemical evolutionary stage, and analyze the observed Planck
cold clumps.
