Effects of cosmic rays on hydrocarbon interstellar dust

¹ Institut d’Astrophysique Spatiale, Univ. Paris-Sud, Bât. 121, 91405 Orsay, France
² Astrochemistry Laboratory (Code 691), NASA Goddard Space Flight Center, Building 34, 8800 Greenbelt Road, Greenbelt, MD 20771, USA
³ Institut des Sciences Moléculaires d’Orsay, Univ. Paris-Sud, Bât. 210, 91405 Orsay, France
⁴ Institut de Physique Nucléaire d’Orsay, Univ. Paris-Sud, Bât. 102, 91405 Orsay, France
⁵ Laboratoire de Physique des Lasers, Atomes et Molécules, Univ. Lille 1, Bât. P5, 59655 Villeneuve d’ Ascq Cedex, France
⁶ Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, Univ. Paris-Sud, Bât. 104, 91405 Orsay, France

Abstract

Hydrogenated amorphous carbons, an important component of the interstellar carbonaceous dust, possess infrared spectral signatures (at 3.4, 6.9 and 7.3 μm) that are ubiquitous in the diffuse interstellar medium of galaxies, but not observed in dense clouds. To better understand the role played by cosmic rays in the disappearance of these absorption bands, irradiation experiments of hydrocarbon dust analogues have been performed with different swift ions. The results obtained through the in situ infrared monitoring of the samples during the irradiations allow to infer the dehydrogenation effect of the cosmic ray distribution on the interstellar hydrogenated amorphous carbons. The importance of this interstellar dust destruction by cosmic rays is discussed in comparison to other energetic processes in different interstellar environments.