SpringerLink
Forum Springer Astron. Astrophys.
Forum Whats New Search Orders


Astron. Astrophys. 363, L5-L8 (2000)

Next Section Table of Contents

Letter to the Editor

Dehydrogenation of polycyclic aromatic hydrocarbons in the diffuse interstellar medium

M.H.Vuong and B.H. Foing

Solar System Division, ESA Space Science Department, ESTEC/SO, 2200 AG Noordwijk, The Netherlands (vuong@obs-nice.fr, bfoing@estec.esa.nl)

Received 28 July 2000 / Accepted 17 October 2000

Abstract

We present a model for the hydrogenation states of Polycyclic Aromatic Hydrocarbons (PAHs) in the diffuse interstellar medium. First, we study the abundance of hydrogenation and charge states of PAHs due to photo-ionization, photo-dissociation in the interstellar UV field, electron recombination and chemical reactions between PAH cations and H or H2. For PAH cations, we find that the dehydrogenation effects are dominant. The hydrogenation state of PAHs depends strongly on the H density, the size of molecule and UV field. In diffuse clouds with low H density and normal UV radiation, PAHs containing less than 40 C are completely or strongly dehydrogenated whereas at high H density, they are normally hydrogenated. The partially dehydrogenated species dominate in intermediate density clouds. PAHs above 40 C are quite stable and are fully hydrogenated, which would favor their spectroscopic search in near IR surveys of Diffuse Interstellar Bands (DIBs).

Key words: ISM: molecules – ISM: clouds – ISM: dust, extinction

Present address: Observatoire de la Côte d'Azur, Département Fresnel, 06304 Nice Cedex, France

Send offprint requests to: Bernard H. Foing

This article contains no SIMBAD objects.

Contents