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Title: Any old iron? : astrochemical modelling of star-forming regions at low metallicity
Author: Kunawicz, Nadya
ISNI:       0000 0004 2696 3956
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2010
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Two pseudo-time-dependent chemical models have been utilised - one of a dark cloud,and one of a hot core - in order to model these clouds in low metallicity environments, such as other galaxies. The dark cloud model uses gas-phase chemistry, whereas the hot core model includes both gas-phase and surface chemistry. The simulations have been calculated with varying initial elemental abundances of C, O, N, S and the heavy metals Fe, Mg and Na (henceforth, M). These initial abundances are taken from observations of HII regions in the Galaxy, the Large Magellanic Cloud and the Small Magellanic Cloud. The results have been used to identify species which potentially trace the underlying metallicity in dark clouds and hot cores. In the dark cloud models, the most useful tracers are ratios of two species, notably CO/OH and HCO+/CO, which trace the underlying C and M abundances respectively. In the hot core models, the most useful metallicity tracer species are HNC and NH3. The HNC abundance traces an underlying change in metallicity, independent of any changes to the dust/gas ratio. The NH3 abundance traces the underlying N abundance. The hot core model output abundances were used with RATRAN, a non-LTE radiative transfer code, to predict the integrated intensity as a function of hot core radius for various species. The RATRAN results are more directly comparable with observations than the results from the chemical models. Less common isotopes have been used to limit the optical depth of the species modelled. The results show that the extent of the emission may not reflect the size of the hot core. HN13C and NH3 are confirmed as the most useful metallicity tracer species in hot cores.
Supervisor: Markwick, Andrew Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available