Journal Article

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

Mohsen Nejad-Asghar

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 414, issue 1, pages 470-478
Published in print June 2011 | ISSN: 0035-8711
Published online June 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.18412.x
Formation of low-mass condensations in molecular cloud cores via thermal instability

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Low-mass condensations (LMCs) have been observed within molecular cloud cores. In this study, we investigate the effect of the application of isobaric thermal instability (TI) in forming these LMCs. For this purpose, we first investigate the occurrence of TI in molecular clouds. Then, to study the significance of linear isobaric TI, we use a contracting axisymmetric cylindrical core with an axial magnetic field. Consideration of cooling and heating mechanisms in molecular clouds shows that including the heating due to ambipolar diffusion can lead to the occurrence of TI on a time-scale smaller than the dynamical time-scale. Application of linear perturbation analysis shows that isobaric TI can take place in the outer regions of molecular cloud cores. Furthermore, the results show that perturbations with wavelengths greater than few astronomical units are protected from the destabilization property of thermal conduction, so that 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 protostellar entities, brown dwarfs or protoplanets.

Keywords: diffusion; hydrodynamics; stars: formation; ISM: clouds; ISM: evolution; ISM: magnetic fields

Journal Article.  5741 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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