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Title: A semi-empirical model of the spectra of dusty galaxies
Author: Ford, D. C.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2008
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In this thesis, a semi-empirical model for the infrared emission of dust around star-forming sites in galaxies is developed and then applied to fitting a variety of observations. A simple model of radiative transport in dust clouds is combined with a state-of-the-art model of the microscopic optical properties of interstellar dust grains. In combination with the STARBURST99 stellar spectral synthesis package, this framework is able to produce synthetic spectra for galaxies which extend from the Lyman limit through to the far-infrared. Models of radiative transport in dusty media and of the optical properties of dust grains both have potential to be computationally time-consuming. This has restricted previous semi-empirical models to include detailed considerations of only one of these. In this thesis, a minimal set of simplifications are adopted in the treatment of radiative transport, such that the use of a state-of-the-art model of dust grain energetics is computationally tractable. Following an initial exploration of the predictions of the model, it is applied to fitting the spectra of M82, Arp220 and NGC 6381. M82 and Arp220 are chosen for study because they are nearby starburst galaxies, and test the ability of our model to fit extreme systems. In both cases, we need to remove some of the smallest grains from our model to fit their mid-infrared spectra, but achieve an excellent fit after doing so. NGC 6381 is chosen because it is the only NGC or UGC galaxy within the xFLS field. From our model fit, we infer a flat star formation history over the past (150±50)Myr with star-formation rate (4.69 ± 0.37) M yr-1, and that these stars are surrounded by a column density (6 ± 1) x 1025 Hm-2  of material and an old stellar population of mass (95 ± 5) x 109 M.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available