Gas emissions in Planck cold dust clumps---A Survey of the J=1-0
  Transitions of $^{12}$CO, $^{13}$CO, and C$^{18}$O
  A survey toward 674 Planck cold clumps of the Early Cold Core Catalogue (ECC)
in the J=1-0 transitions of $^{12}$CO, $^{13}$CO and C$^{18}$O has been carried
out using the PMO 13.7 m telescope. 673 clumps were detected with the $^{12}$CO
and $^{13}$CO, and 68% of the samples have C$^{18}$O emission. Additional
velocity components were also identified.A close consistency of the three line
peak velocities was revealed for the first time. Kinematic distances are given
out for all the velocity components and half of the clumps are located within
0.5 and 1.5 kpc. Excitation temperatures range from 4 to 27 K, slightly larger
than those of $T_d$. Line width analysis shows that the majority of ECC clumps
are low mass clumps. Column densities N$_{H_{2}}$ span from 10$^{20}$ to
4.5$\times10^{22}$ cm$^{-2}$ with an average value of
(4.4$\pm$3.6)$\times10^{21}$ cm$^{-2}$. N$_{H_{2}}$ cumulative fraction
distribution deviates from the lognormal distribution, which is attributed to
optical depth. The average abundance ratio of the $^{13}$CO to C$^{18}$O in
these clumps is 7.0$\pm$3.8, higher than the terrestrial value. Dust and gas
are well coupled in 95% of the clumps. Blue profile, red profile and line
asymmetry in total was found in less than 10% of the clumps, generally
indicating star formation is not developed yet. Ten clumps were mapped. Twelve
velocity components and 22 cores were obtained. Their morphologies include
extended diffuse, dense isolated, cometary and filament, of which the last is
the majority. 20 cores are starless.Only 7 cores seem to be in gravitationally
bound state. Planck cold clumps are the most quiescent among the samples of
weak-red IRAS, infrared dark clouds, UC H{\sc ii} region candidates, EGOs and
methanol maser sources, suggesting that Planck cold clumps have expanded the
horizon of cold Astronomy.
