Polycyclic aromatic hydrocarbon processing in a hot gas

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

172 citations recorded by the source corpus.

Context. PAHs are thought to be a ubiquitous and important dust component of the interstellar medium. However, the effects of their immersion in a hot (post-shock) gas have never before been fully investigated. Aims. We study the effects of energetic ion and electron collisions on PAHs in the hot post-shock gas behind interstellar shock waves. Methods. We calculate the ion-PAH and electron-PAH nuclear and electronic interactions, above the carbon atom loss threshold, in H ii regions and in the hot post-shock gas for temperatures ranging from 10 3 −10 8 K. Results. PAH destruction is dominated by He collisions at low temperatures (T < 3 × 10 4 K), and by electron collisions at higher temperatures. Smaller PAHs are destroyed faster for T < 10 6 K, but the destruction rates are roughly the same for all PAHs at higher temperatures. The PAH lifetime in a tenuous hot gas (nH ≈ 0.01 cm −3 , T ≈ 10 7 K), typical of the coronal gas in galactic outflows, is found to be about thousand years, orders of magnitude shorter than the typical lifetime of such objects. Conclusions. In a hot gas, PAHs are principally destroyed by electron collisions and not by the absorption of X-ray photons from the hot gas. The resulting erosion of PAHs occurs via C2 loss from the periphery of the molecule, thus preserving the aromatic structure. The observation of PAH emission from a million degree, or more, gas is only possible if the emitting PAHs are ablated from dense, entrained clumps that have not yet been exposed to the full effect of the hot gas.

Subfields: Astronomy and Astrophysics, Instrumentation, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/124f76ec783a42d86946cbb5bb204f6a4f75a0e4

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Instrumentation

In Statistical and Nonlinear Physics

L. Testi

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.”
A gallery of bubbles. The nature of the bubbles observed by Spitzer and what ATLASGAL tells us about the surrounding neutral material (2010, background): “However, the study by Micelotta et al. (2010) of the interaction of PAHs with electrons or ions (H+ and He+) in a hot or warm gas shows that PAH destruction is dominated by He+ collisions at a temperature lower than 30 000 K, thus is dominant in H ii regions.”
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.”