Automated Processing and Analysis of Galactic Neutral Hydrogen Absorption Observations

Abstract

In this research project I analysed the composition and structure of the cold neutral hydrogen (H i) gas at the locations of the MAGMO (Mapping the Galactic Magnetic field through OH masers) survey observations. To enable this analysis I developed an automated pipeline and used that to produce H i absorption and emission spectra from the MAGMO observations. This pipeline was designed with the aim of being applicable to future large surveys such as GASKAP, the Galactic Australian SKA Pathfinder survey.

The MAGMO observations targeted the sites of 6.7-GHz methanol masers, which are associated with star-forming regions. These very active regions have complex structures with bubbles formed by stellar winds from young, high mass stars. In these regions it is reasonable to expect there will be significant reserves of cold gas. The MAGMO H i dataset provided an excellent opportunity to examine the cold neutral medium (CNM) towards these regions and to compare it with the overall CNM population.

In Chapter 2 I provide a summary of the current knowledge of the Milky Way’s cold H i gas and an introduction to other topics which will assist the reader in understanding the analysis. Chapter 3 provides a detailed description of the data, and the pipeline developed for its analysis. This is more detailed than is typical in order to explain the decisions in developing the automated processing. In Chapter 4 I provide the results from the observations. In Chapter 5 I compare the results to results from similar studies, discuss the overall findings and assess the effectiveness of the processing pipeline. Finally in Chapter 6 I summarise the main findings and discuss future potential for both this data set and the processing pipeline.