Volume 542, June 2012
|Number of page(s)||17|
|Section||Interstellar and circumstellar matter|
|Published online||12 June 2012|
Physical properties of interstellar filaments
1 Canadian Institute for Theoretical Astrophysics, University
of Toronto, 60 St. George Street, ON M5S3H8, Canada
2 Research School of Astronomy Astrophysics, Institute of Advanced Studies, The Australian National University, Cotter Road, Weston Creek, ACT 2611, Australia
Accepted: 13 April 2012
We analyze the physical parameters of interstellar filaments that we describe by an idealized model of isothermal self-gravitating infinite cylinder in pressure equilibrium with the ambient medium. Their gravitational state is characterized by the ratio fcyl of their mass line density to the maximum possible value for a cylinder in a vacuum. Equilibrium solutions exist only for fcyl < 1. This ratio is used in providing analytical expressions for the central density, the radius, the profile of the column density, the column density through the cloud centre, and the FWHM. The dependence of the physical properties on external pressure and temperature is discussed and directly compared to the case of pressure-confined isothermal self-gravitating spheres. Comparison with recent observations of the FWHM and the central column density NH(0) show good agreement and suggest a filament temperature of ~10 K and an external pressure in the range 1.5 × 104 K cm-3 to 5 × 104 K cm-3. Stability considerations indicate that interstellar filaments become increasingly gravitationally unstable with mass line ratio fcyl approaching unity. For intermediate fcyl > 0.5 the instabilities should promote core formation through compression, with a separation of about five times the FWHM. We discuss the nature of filaments with high mass line densities and their relevance to gravitational fragmentation and star formation.
Key words: stars: formation / ISM: clouds / ISM: structure / submillimeter: ISM / infrared: ISM
© ESO, 2012
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