Physical properties of Planck Cold Dust Clumps

To explore physical properties of Planck cold dust clumps, 674 of the pilot samples were observed at the 13.7 m telescope of Purple Mountain Observatory (PMO) in J = 1 – 0 transitions of CO, 13 CO and C 18 O. HCO + , HCN and N 2 H + emissions were also observed with PMO 13.7 m and IRAM 30 m telescopes. They are real cold and quiescent with mean T k ∼ 10 K and mean FWHM of 13 CO (1–0) 1.27 km s −1 . Column density ranges from 10 20 to 10 22 cm −2 . Gas of the Planck clumps extends molecular space in the Milky Way. Turbulence dominates in cores. Filament structure is the majority and most of the cores are starless. Ten percent of the cores show asymmetric emission features including blue- and red- profiles. Planck clumps include different cold or low luminosity sources. Dense cores constitute an ideal sample for studying initial state of star formation while the diffuse clumps are suitable for investigating the formation of cores.