Decoding the kinematic and ionisation structure of axisymmetric nebulae

The aim of the thesis was to develop a code and pipeline for generating 3D photoionisation models of axisymmetric nebulae to better understand their ob- served structure and composition. This was achieved through a new code that amalgamated the features of popular (but separate) codes in astronomy; a 3D morpho-kinematic modelling application called Shape, a well known, large-scale spectral synthesis code called Cloudy and PyCloudy, a Python library that handles Cloudy. The resulting code presented in this thesis was called Py- Cross, an acronym for “PyCloudy Rendering of Shape Software”. The steep learning curves traditionally experienced when developing and using new codes overshadows the necessity for a formal software development lifecycle. As software development and coding is becoming an essential skill for new astronomers, who are often required to create their own codes for specific purposes, employing and adhering to a software development lifecycle during developing will help meet milestones while managing complex projects, thus ensuring reliability and quality. Here, a formal software development lifecycle and test driven development approach is described and employed in the development of the PyCross code. A detailed account of the code development, installation, functionality, user interface and operational overview is given using both theoretical and actual stellar objects. Creating photoionisation models for known planetary nebulae and novae can only be accomplished when there is sufficient information to determine the most significant physical parameters of the nebula and the central star. Presented here are novel approaches for various scientific methods/pipelines that can be employed with PyCross to generate photoionisation models. Over the course of this thesis PyCross has been used to develop, for the first time, 3D photoionisation models of novae V5668 Sagittarii (2015), V4362 Sagittarii (PTB 42) as well as planetary nebulae LoTr 1 and MyCn 18