EDP Sciences
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Volume 428, Number 1, December II 2004
Page(s) 99 - 108
Section Interstellar and circumstellar matter
DOI http://dx.doi.org/10.1051/0004-6361:20034137

A&A 428, 99-108 (2004)
DOI: 10.1051/0004-6361:20034137

On the thermal behaviour of small iron grains

J. Fischera

Research School of Astronomy & Astrophysics, Institute of Advanced Studies, The Australian National University, Cotter Road, Weston Creek, ACT 2611, Australia
    e-mail: fischera@mso.anu.edu.au

(Received 31 July 2003 / Accepted 28 July 2004)

The optical properties of small spherical iron grains are derived using a Kramers-Kronig-consistent model of the dielectric function including its dependence on temperature and size. Especially discussed is the effect of the size dependence, which results from the limitation of the free path of the free electrons in the metal by the size of the grain, on the absorption behaviour of small iron spheres and spheroids. The estimated absorption properties are applied to study the temperature behaviour of spherical and spheroidal grains which are heated by the interstellar radiation field.

Key words: ISM: dust, extinction -- ISM: general

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