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Cycling of dust grains through the galactic halo

Published online by Cambridge University Press:  12 April 2016

A. Ferrara
Affiliation:
Dipartimento di Astronomia, Università di Firenze, Firenze, Italy
J. Franco
Affiliation:
Instituto de Astronomía, UNAM, México City, México
B. Barsella
Affiliation:
Istituto di Astronomia, Università di Pisa, Pisa, Italy
F. Ferrini
Affiliation:
Istituto di Astronomia, Università di Pisa, Pisa, Italy

Abstract

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The analysis of the vertical motion of dust grains inside the disk of spiral galaxies shows that grains at high latitudes (z/H > 0.3 — 0.5, where H is the scale height of the gaseous disk) can be removed from the gaseous disk by radiation pressure from field stars. Once the dust particles are located at the base of the galactic corona, and neglecting the presence of magnetic fields, their motion is determined by the global light and mass distributions. We follow the dynamical evolution of grains embedded in a hot galactic corona (T ≥ 105 K and n ≤ 10−2 cm−3), including drag and sputtering. We find that typical sputtering time scales are larger than 108 yrs, and, in these times scales, the grains can travel large radial and vertical distances from their original positions. This process can remove grains from the inner part of a galaxy and send them to large galactocentric distances. The evolution resembles a dusty galactic fountain which may pollute the outer galaxy with grains and heavy elements. Similarly, for some cases the dust particles can be detached from the galactic gravitational field and they are expelled to the intergalactic medium. In these cases, the chemical pollution is not restricted to the host galaxy and may reach material which is otherwise primordial.

Type
VI. Interstellar Matter at High Galactic Latitudes
Copyright
Copyright © Springer-Verlag 1989

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