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Chemical and radiative transfer modelling of the ISO-LWS Fabry-Perot spectra of Orion-KL water lines

Lerate, MR; Yates, JA; Barlow, MJ; Viti, S; Swinyard, BM; (2010) Chemical and radiative transfer modelling of the ISO-LWS Fabry-Perot spectra of Orion-KL water lines. Monthly Notices of the Royal Astronomical Society , 406 (4) pp. 2445-2451. 10.1111/j.1365-2966.2010.16478.x. Green open access

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Abstract

We present chemical and radiative transfer models for the many far-infrared ortho- and para-H2O lines that were observed from the Orion-KL region in high resolution Fabry-Pérot (FP) mode by the Long Wavelength Spectrometer (LWS) on board the Infrared Space Observatory (ISO). The chemistry of the region was first studied by simulating the conditions in the different known components of Orion-KL: chemical models for a hot core, a plateau and a ridge were coupled with an accelerated Λ-iteration radiative transfer model to predict H2O line fluxes and profiles. Our models include the first 45 energy levels of ortho- and para-H2O. We find that lines arising from energy levels below 560 K were best reproduced by a gas of density 3 × 105 cm−3 at a temperature of 70–90 K, expanding at a velocity of 30 km s−1 and with a H2O/H2 abundance ratio of the order of 2–3 × 10−5, similar to the abundance derived by Cernicharo et al. However, the model that best reproduces the fluxes and profiles of H2O lines arising from energy levels above 560 K has a significantly higher H2O/H2 abundance, 1–5 × 10−4, originating from gas of similar density, in the Plateau region, that has been heated to 300 K, relaxing to 90–100 K. We conclude that the observed water lines do not originate from high-temperature shocks.

Type: Article
Title: Chemical and radiative transfer modelling of the ISO-LWS Fabry-Perot spectra of Orion-KL water lines
Open access status: An open access version is available from UCL Discovery
DOI: 10.1111/j.1365-2966.2010.16478.x
Publisher version: https://doi.org/10.1111/j.1365-2966.2010.16478.x
Language: English
Additional information: This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: line: identification, surveys, ISM: individual: Orion, ISM: lines and bands, ISM: molecules, infrared: ISM
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Computer Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI: https://discovery.ucl.ac.uk/id/eprint/10095509
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