Self-generated ultraviolet radiation in molecular shock waves
| Autor: | G. Pineau des Forêts, Benjamin Godard, A. Lehmann, E. Falgarone |
|---|---|
| Přispěvatelé: | Université de Picardie Jules Verne (UPJV), HTL - Histoire des Théories Linguistiques - UMR 7597 (HTL), Université Sorbonne Nouvelle - Paris 3-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS) |
| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
Shock wave
Photon Opacity Astrophysics::High Energy Astrophysical Phenomena Astrophysics ISM: atoms Kinetic energy 01 natural sciences methods: numerical 0103 physical sciences Radiative transfer 010303 astronomy & astrophysics Astrophysics::Galaxy Astrophysics Physics ISM: kinematics and dynamics 010308 nuclear & particles physics Astronomy and Astrophysics shock waves Photoelectric effect Astrophysics - Astrophysics of Galaxies ISM: molecules 3. Good health Supernova 13. Climate action Space and Planetary Science radiative transfer Intergalactic travel [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] |
| Zdroj: | Astronomy and Astrophysics-A&A Astronomy and Astrophysics-A&A, EDP Sciences, 2020, 643, pp.A101. ⟨10.1051/0004-6361/202038644⟩ |
| ISSN: | 0004-6361 |
| Popis: | Shocks are ubiquitous in the interstellar and intergalactic media, where their chemical and radiative signatures reveal the physical conditions in which they arise. Detailed astrochemical models of shocks at all velocities are necessary to understand the physics of many environments including protostellar outflows, supernova remnants, and galactic outflows. We present an accurate treatment of the self-generated UV radiation in intermediate velocity, stationary, weakly magnetised, J-type, molecular shocks. Shock solutions computed with the Paris-Durham shock code are post-processed using a multi-level accelerated $\Lambda$-iteration radiative transfer algorithm to compute Ly$\alpha$, Ly$\beta$, and 2-photon continuum emission. The subsequent impacts on the ionisation and dissociation of key atomic and molecular species as well as on the heating by the photoelectric effect take the wavelength dependent cross-sections and the fluid velocity profile into account. We analyse shock models with velocities $V=25-60$ km/s, propagating in dense ($n \geq 10^4$ ${\rm cm}^{-3}$), shielded gas. Self-absorption traps Ly$\alpha$ photons in a small region in the shock, though a large fraction escapes into the line wings. We find a critical velocity $V\sim 30$ km/s above which shocks produce a Ly$\alpha$ photon flux exceeding that of the standard ISRF. The escaping photons generate a warm slab (T~100 K) ahead of the shock as well as pre-ionise C and S. These shocks are traced by bright atomic fine structure (e.g. O and S) and metastable (e.g. O and C) lines, substantive molecular emission (e.g. H2, OH, and CO), enhanced column densities of several species (e.g. CH+ and HCO+), as well as a severe destruction of H2O. As much as 13-21% of the initial kinetic energy of the shock escapes in Ly$\alpha$ and Ly$\beta$ photons if the dust opacity in the radiative precursor allows it. Comment: Accepted for publication in A&A, 16 main body pages, 8 appendices pages |
| Databáze: | OpenAIRE |
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