Physical properties of Planck Cold Dust Clumps

¹ Astronomy Dept., Peking Univ., Beijing, China
² Korea Astronomy and Space Science Institute, Daejeon, Korea
³ I. Physical Institute, University of Cologne, Germany
⁴ Key Lab of Radio Astronomy, NAOC, Chinese Academy of Sciences, Beijing, China
⁵ Department of Astronomy, Yunnan University, Yunna, China
⁶ Purple Mountain Observatory, Qinghai Station, Qinghai, China

e-mail: ywu@pku.edu.cn

Abstract

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, ¹³CO and C¹⁸O. HCO⁺, HCN and N₂H⁺ 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 ¹³CO (1–0) 1.27 km s⁻¹. Column density ranges from 10²⁰ to 10²² 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.