Origin of High-Speed Non-Thermal Flow Due to the Collisions of Molecular Cloud Clumps

Abstract

It is well-known that there is non-thermal flow in molecular clouds. Its origin is frequently discussed in the context of star-formation. Interestingly, non-thermal flow has two components of the velocity field. One of the two is the so-called turbulent component, and its velocity dispersion is expressed as σc, which is called the core-component. The other is the wing-component, and its dispersion is denoted as σw. There is a characteristic relation between those two components, σw ∼ 3 × σc. In this paper, we present a simple derivation of this core-wing relation, assuming that the wing component originates in the collisions of small clumps, which have been suggested observationally in molecular clouds and their cores. Throughout our discussions, we insist that the core-wing relation is a reminiscence of the shock property in a moment of collisions of the clumps.