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Monte Carlo predictions of far-infrared emission from spiral galaxies

Bianchi, S., Davies, Jonathan Ivor and Alton, P. B. 2000. Monte Carlo predictions of far-infrared emission from spiral galaxies. Astronomy & Astrophysics 359 (1) , pp. 65-81.

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Abstract

We present simulations of Far Infrared (FIR) emission by dust in spiral galaxies, based on the Monte Carlo radiative transfer code of \citet*{BianchiApJ1996}. The radiative transfer is carried out at several wavelength in the Ultraviolet (UV), optical and Near Infrared (NIR), to cover the range of the stellar Spectral Energy Distribution (SED). Together with the images of the galactic model, a map of the energy absorbed by dust is produced. Using Galactic dust properties, the spatial distribution of dust temperature is derived under the assumption of thermal equilibrium. A correction is applied for non-equilibrium emission in the Mid Infrared (MIR). Images of dust emission can then be produced at any wavelength in the FIR. We show the application of the model to the spiral galaxy NGC 6946. The observed stellar SED is used as input and models are produced for different star-dust geometries. It is found that only optically thick dust disks can reproduce the observed amount of FIR radiation. However, it is not possible to reproduce the large FIR scalelength suggested by recent observation of spirals at 200 mu m, even when the scalelength of the dust disk is larger than that for stars. Optically thin models have ratios of optical/FIR scalelengths closer to the 200 mu m observations, but with smaller absolute scalelengths than optically thick cases. The modelled temperature distributions are compatible with observations of the Galaxy and other spirals. We finally discuss the approximations of the model and the impact of a clumpy stellar and dust structure on the FIR simulations.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Uncontrolled Keywords: radiative transfer – ISM: dust, extinction – galaxies: individual: NGC 6946 – galaxies: spiral – galaxies: structure – infrared: galaxies
Additional Information: Pdf uploaded in accordance with publisher's policy at http://www.sherpa.ac.uk/romeo/issn/0004-6361/ (accessed 16/04/2014)
Publisher: EDP Sciences
ISSN: 1432-0746
Date of First Compliant Deposit: 30 March 2016
Last Modified: 04 Jun 2017 04:23
URI: http://orca-mwe.cf.ac.uk/id/eprint/38117

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