Starbursts Triggered by Central Overpressure. II. A Parameter Study

Jog, Chanda J and Das, Mousumi (1996) Starbursts Triggered by Central Overpressure. II. A Parameter Study. In: The Astrophysical Journal, 473 (2 Part). pp. 797-805.

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Abstract

A parameter study is made of the radiative shock compression of a disk molecular cloud due to the high pressure of the central molecular intercloud medium, after the cloud has fallen into the central region of a galaxy following a galaxy interaction. The dependence of the compression on the disk cloud and central gas parameters has been studied. We show that $f_{shell}$, the fraction of cloud mass compressed in the outer shell that becomes unstable, it is a function of only the external pressure, the cloud radius, and the cloud density. We find that for a wide range of values for the input parameters, $f_{shell}$ is high and lies between 0.75 to 0.90. The fraction $f_{shell}$ is not sensitively dependent on the value of the central gas pres-sure because the initial inward shock velocity is proportional to the square root of the central pressure, and at later stages it is determined mainly by the self-gravity of the shocked shell. Thus, star formation triggered in disk clouds by compression by the central overpressure, as proposed by Jog & Das, is a general triggering mechanism and is valid as long as the central gas has an overpressure of even a factor of a few higher than that of the incoming disk molecular clouds. We apply the mechanism to the galaxies for which the central gas parameters are known; for example, IC 342 and NGC 1808. We find that in both cases a large fraction of the cloud mass will be compressed. Hence, these galaxies should show a central starburst, provided that there is a substantial gas infall rate from the disk to the central region. This agrees with observations, in that NGC 1808 with gas infall due to galaxy interaction has a central starburst, while IC 342 does not.

Item Type:	Journal Article
Publication:	The Astrophysical Journal
Publisher:	American Astronomical Society.
Additional Information:	Copyright of this article belongs to American Astronomical Society.
Keywords:	Galaxies;Interactions - galaxies;ISME galaxies;Starburst- hydrodynamics -shock waves-stars;Formation - galaxies;ISM
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	22 Dec 2006
Last Modified:	19 Sep 2010 04:33
URI:	http://eprints.iisc.ac.in/id/eprint/9154

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