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Internal heating of molecular clouds by tidal fields

Das, M and Jog, CJ (1995) Internal heating of molecular clouds by tidal fields. In: Astrophysical Journal, 451 (1 part 1). pp. 1567-175.

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Presents a study of the effect of the galactic tidal field on the internal energy of molecular clouds, moving in the disk or central bar potential of a galaxy. During epicyclic motion or orbital motion in a bar, the tidal field across a cloud varies with time. This time variation of the tidal field across the cloud couples the rotational motion in the galaxy to the internal clump motion within the cloud. There will be a net exchange of internal energy between the cloud and the external gravitational field of the galaxy. The authors have examined this effect to see whether tidal fields are an important heating mechanism for molecular clouds and hence important for cloud support. An N-body simulation method has been used to treat the motion of clumps in molecular clouds. The authors find that the heating effect of the tidal field is not important for epicyclic motion, but it is significant for a cloud moving in a bar potential. For a cloud of mass $5×10^4 M_&odot$;, the change in internal energy is 10%-15% of the initial internal energy. Thus, although tidal fields alone cannot provide the energy required for cloud support, their contribution is significant in a bar potential. Also, some clumps become unbound from the cloud during the bar orbits. This can explain the origin of diffuse molecular gas which has been observed in the central regions of galaxies like the Galaxy, IC 342, and NGC 1808. The authors also find that an initially virialized cloud is not disrupted by the tidal field after a few rotations in the bar potential.

Item Type: Journal Article
Publication: Astrophysical Journal
Publisher: University of Chicago Press
Additional Information: Copyright of this article belongs to University Of Chicago Press.
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 20 Nov 2006
Last Modified: 27 Aug 2008 12:22
URI: http://eprints.iisc.ac.in/id/eprint/8610

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