Polycyclic aromatic hydrocarbon processing in interstellar shocks

By E. Micelotta, A. Jones, A. Leiden, Leiden University, The Netherlands., I. D. Spatiale, Universite de Paris Sud, Cnrs, Orsay, France. and 3 more. 2009

219 citations recorded by the source corpus.

Context. PAHs appear to be an ubiquitous interstellar dust component but the effects of shocks waves upon them have never been fully investigated. Aims. We study the effects of energetic (≈0.01−1 keV) ion (H, He and C) and electron collisions on PAHs in interstellar shock waves. Methods. We calculate the ion-PAH and electron-PAH nuclear and electronic interactions, above the threshold for carbon atom loss from a PAH, in 50−200 km s −1 shock waves in the warm intercloud medium. Results. Interstellar PAHs (NC = 50) do not survive in shocks with velocities greater than 100 km s −1 and larger PAHs (NC = 200) are destroyed for shocks with velocities ≥125 km s −1 . For shocks in the ≈75−100 km s −1 range, where destruction is not complete, the PAH structure is likely to be severely denatured by the loss of an important fraction (20−40%) of the carbon atoms. We derive typical PAH lifetimes of the order of a few ×10 8 yr for the Galaxy. These results are robust and independent of the uncertainties in some key parameters that have yet to be well-determined experimentally. Conclusions. The observation of PAH emission in shock regions implies that that emission either arises outside the shocked region or that those regions entrain denser clumps that, unless they are completely ablated and eroded in the shocked gas, allow dust and PAHs to survive in extreme environments.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/6e571f022a9f6c3df4106d59d8aa92a4c2eeb62a

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Citations in the corpus

The global dust SED: tracing the nature and evolution of dust with DustEM (2010, background): “However, given the results for the processing of a-C:H/HAC dust and PAHs (Serra Dı́az-Cano & Jones 2008; Micelotta et al. 2010b,a), the Fig.”
The evolution of amorphous hydrocarbons in the ISM: dust modelling from a new vantage point (2013, background): “…rather complex, sizedependent evolution arising, principally, from ultraviolet (UV) photon absorption leading to photo- or thermal-processing (e.g., Jones 2009, 2012a,b,c) and incident ion and electron collisions in shock waves and in a hot gas (e.g., Micelotta et al. 2010a,b; Bocchio et al. 2012).”
The Molecular Universe (2011, unknown): “In the ISM, these molecular species will be further processed by UV and X-ray photons and by energetic particles in shock waves, hot gas or cosmic rays (Micelotta et al. 2010a,b, 2011), before becoming incorporated into regions of star and planet formation.”