Formation of low-mass condensations in the molecular cloud cores via thermal instability

TL;DR

This paper investigates how isobaric thermal instability can lead to the formation of low-mass condensations in molecular cloud cores, providing a potential explanation for their origin as precursors to stars and planets.

Contribution

It demonstrates that thermal instability, influenced by ambipolar diffusion heating, can occur in molecular clouds and lead to the formation of low-mass condensations.

Findings

Thermal instability can occur in outer regions of molecular cloud cores.

Perturbations larger than a few astronomical units can grow into condensations.

Thermal conduction stabilizes smaller perturbations, allowing larger ones to develop.

Abstract

The low-mass condensations (LMCs) have been observed within the molecular cloud cores. In this research, we investigate the effect of isobaric thermal instability (TI) applied for forming these LMCs. For this purpose, at first we investigate the occurrence of TI in the molecular clouds. Then, for studying the significance of linear isobaric TI, we use a contracting axisymmetric cylindrical core with axial magnetic field. Consideration to cooling and heating mechanisms in the molecular clouds shows that including the heating due to ambipolar diffusion can lead to the occurrence of TI in a time-scale smaller than dynamical time-scale. Application of linear perturbation analysis shows that isobaric TI can take place in outer region of the molecular cloud cores. Furthermore, the results showthat perturbations with wavelengths greater than few astronomical units are protected from destabilization property of thermal conduction, so they can grow to form LMCs. Thus, the results show that the mechanism of TI can be used to explain the formation of LMCs as the progenitors of collapsing proto-stellar entities, brown dwarfs, or proto-planets.