Ultraviolet photoproduction of ISM dust

Free access article

Issue		A&A Volume 432, Number 3, March IV 2005


Page(s)		895 - 908
Section		Interstellar and circumstellar matter
DOI		http://dx.doi.org/10.1051/0004-6361:20042094

A&A 432, 895-908 (2005)
DOI: 10.1051/0004-6361:20042094

Laboratory characterisation and astrophysical relevance

E. Dartois¹, G. M. Muñoz Caro¹, D. Deboffle¹, G. Montagnac² and L. d'Hendecourt¹

¹ Institut d'Astrophysique Spatiale, UMR - 8617, Université Paris-Sud, Bâtiment 121, 91405 Orsay Cedex, France
e-mail: emmanuel.dartois@ias.u-psud.fr
² Laboratoire des Sciences de la Terre, UMR 5570 CNRS, École Normale Supérieure de Lyon, 46 allée d'Italie, 69364 Lyon Cedex 07, France

(Received 30 September 2004 / Accepted 30 October 2004 )

Abstract
The production of a hydrogenated amorphous carbon polymer (a-C:H) via the photolysis of a series of organic molecule precursors at low temperature is described. Such amorphous material is synthesised under interstellar conditions (10 K and Lyman- $\alpha$ photons) and represents the best candidate to explain the Diffuse Interstellar Medium absorption observed in our Galaxy and in other galaxies. We perform a series of laboratory analyses (Infrared spectroscopy, $\mu$ spectroscopy, Raman, Photoluminescence and UV-visible spectroscopy) which allow a full characterisation of such polymers. This allows us to assess the importance of the polymer and possible scenarios for its role in crucial aspects of the lifecycle of dust. Such material has implications for the carbon budget at galactic scales, hydrogen formation, extended red emission, as a PAH precursor, and in explaining the 2175 $\AA$ extinction bump.

Key words: ISM: dust, extinction -- galaxies: ISM -- ISM: lines and bands

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