• Jones, Anthony

Abstract

Carbonaceous matter is an important and ubiquitous component of interstellar dust. However, observations of shocked regions of the interstellar medium (ISM) seem to show that this dust may be rather more easily eroded in shock waves than current models predict. We have therefore recently re-evaluated the life-cycle of carbonaceous materials in the interstellar medium through a study of the erosion of hydrogenated amorphous carbon (a-C:H) grains and PAH molecules in supernova-generated shocks. Here we adopt a-C:H as a more realistic form for the carbon dust, rather than the usually-assumed “graphite.” We find that with a-C:H grains we can get a better agreement with observations. These results imply that the cycling of carbon into and out of dust must be much faster than previously thought, and that the re-formation of hydrocarbon dust in the ISM must be efficient. The evolution of a-C:H grains in the ISM, principally through progressive “aromatisation” and eventual photo- or collisional-fragmentation (in photon-dominated regions and shocks), may be a primary source of the aromatic emission band carriers. We discuss this within the context of the nature of a-C:H carbon dust and its likely evolution in the ISM....

Topics

• impedance spectroscopy
• amorphous
• Carbon
• grain