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Molecular environments of 51 Planck cold clumps in Orion complex

Abstract

A mapping survey towards 51 Planck cold clumps projected on Orion complex was performed with J=1-0 lines of 12^{12}CO and 13^{13}CO at the 13.7 m telescope of Purple Mountain Observatory. The mean column densities of the Planck gas clumps range from 0.5 to 9.5Γ—1021\times10^{21} cmβˆ’2^{-2}, with an average value of (2.9Β±\pm1.9)Γ—1021\times10^{21} cmβˆ’2^{-2}. While the mean excitation temperatures of these clumps range from 7.4 to 21.1 K, with an average value of 12.1Β±\pm3.0 K. The averaged three-dimensional velocity dispersion Οƒ3D\sigma_{3D} in these molecular clumps is 0.66Β±\pm0.24 km sβˆ’1^{-1}. Most of the clumps have ΟƒNT\sigma_{NT} larger than or comparable with ΟƒTherm\sigma_{Therm}. The H2_{2} column density of the molecular clumps calculated from molecular lines correlates with the aperture flux at 857 GHz of the dust emission. Through analyzing the distributions of the physical parameters, we suggest turbulent flows can shape the clump structure and dominate their density distribution in large scale, but not affect in small scale due to the local fluctuations. Eighty two dense cores are identified in the molecular clumps. The dense cores have an averaged radius and LTE mass of 0.34Β±\pm0.14 pc and 38βˆ’30+5_{-30}^{+5} M_{\sun}, respectively. And structures of low column density cores are more affected by turbulence, while those of high column density cores are more concerned by other factors, especially by gravity. The correlation of the velocity dispersion versus core size is very weak for the dense cores. The dense cores are found most likely gravitationally bounded rather than pressure confined. The relationship between MvirM_{vir} and MLTEM_{LTE} can be well fitted with a power law. The core mass function here is much more flatten than the stellar initial mass function. The lognormal behavior of the core mass distribution is most likely determined by the internal turbulence.Comment: Accepted to The Astrophysical Journal Supplement Series (ApJS

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