The expulsion and retention of dust grains by galactic discs

Details The expulsion and retention of dust grains by galactic discs The expulsion and retention of dust grains by galactic discs

Nov 1998

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998mnras.300.1006d&link_type=abstract

Monthly Notices of the Royal Astronomical Society, Volume 300, Issue 4, pp. 1006-1014.

Astronomy and Astrophysics

Astronomy

37

Dust, Extinction, Galaxies: General

Scientific paper

We have constructed a numerical model of a galaxy that consists of a stellar, gas and dust disc imbedded within a dark halo. We have used this model to assess the radiation, gravitational and viscous forces on dust grains and to trace their motion through the interstellar medium over a period of 10^9yr. We conclude that the disc opacity is a crucial factor in understanding the motion of the grains. Large grains (~0.1mum) with low disc opacity will lead to dust expulsion from the stellar disc, while high opacity leads to dust retention. Reasonable disc opacities lead to the recycling of the larger grains from the outer to the inner regions of the galaxy. The larger grains travel at higher velocities than small grains (0.01-0.001mum), and so the smaller grains remain relatively close to their formation sites. Dust can `leak' out over the entire surface of the disc because of the imbalance of radiation and gravitational forces. The dust is dynamically coupled to the gas and so although the gas lags behind the dust it is carried along with it. This explains the close correlation between the far-infrared emission from dust and the gas column density. We use a simple analytical model to show how the dust mass of a galaxy may evolve with time and how a significant fraction (90 per cent) of the total dust mass produced may have been expelled into the intergalactic medium.

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