Introducing PyCross: PyCloudy Rendering Of Shape Software for pseudo 3D ionisation modelling of nebulae

Research into the processes of photoionised nebulae plays a significant part in our understanding of stellar evolution. It is extremely difficult to visually represent or model ionised nebula, requiring astronomers to employ sophisticated modelling code to derive temperature, density and chemical composition. Existing codes are available that often require steep learning curves and produce models derived from mathematical functions. In this article we will introduce PyCross: PyCloudy Rendering Of Shape Software. This is a pseudo 3D modelling application that generates photoionisation models of optically thin nebulae, created using the Shape software. Currently PyCross has been used for novae and planetary nebulae, and it can be extended to Active Galactic Nuclei or any other type of photoionised axisymmetric nebulae. Functionality, an operational overview, and a scientific pipeline will be described with scenarios where PyCross has been adopted for novae (V5668 Sagittarii (2015) & V4362 Sagittarii (1994)) and a planetary nebula (LoTr1). Unlike the aforementioned photoionised codes this application does not require any coding experience, nor the need to derive complex mathematical models, instead utilising the select features from Cloudy/PyCloudy and Shape. The software was developed using a formal software development lifecycle, written in Python and will work without the need to install any development environments or additional python packages. This application, Shape models and PyCross archive examples are freely available to students, academics and research community on GitHub for download (this https URL).