A multifrequency study of supernova remnants in the Large Magellanic Cloud

Abstract

Supernova remnants (SNRs) are the structures left behind after the explosive death of a star - the supernova (SN). They are responsible for the chemical enrichment of galaxies and inject massive amounts of energy into their surroundings. As they play a significant role in the dynamical and chemical evolution of galaxies, understanding them is of great importance. In this study, I look toward the SNR population of the Large Magellanic Cloud (LMC) - an irregular dwarf galaxy located at a distance of ~ 50 kpc. The LMC is an ideal laboratory for astronomers due to the numerous favourable attributes that aid in observations, e.g., its relatively close proximity, low foreground absorption, and nearly face on orientation. Although emission across the electromagnetic spectrum is included in this study, the primary focus is on emission in the radio-continuum. Hence, the majority of the data used in this thesis consists of pointed and mosaic observations taken with the Australia Telescope Compact Array - a radio interferometer consisting of six 22-m telescopes. Depending on the set-up of this array, the observations may result in high-resolution images - used to study the intricate structure of the remnants, or low resolution images, for obtaining total flux measurements. The first component of this work looks into the individual SNRs and the candidates, adding to the population with the discovery and classification of new SNRs and (re)measuring known remnants. The result of this is the most comprehensive catalogue of SNRs in the LMC. In this catalogue, multi-frequency morphologies of the remnant were examined and various properties were measured, such as the size, integrated flux density measurements at several radio-continuum frequencies - leading to the resulting radio spectral indices, polarisation (and Faraday rotation where possible), star formation history and star formation rates of the surrounding environment, surface-brightness, and luminosity. The second portion of this work makes use of the properties measured and recorded in the catalogue in conjunction with properties (e.g., age) from the literature to carry out basic statistical analysis to inspect the entire population of SNRs in the LMC. This allows astronomers to track the evolution of SNRs, and investigate how certain properties (spectral index, surface brightness etc.) changed as they aged. Further, it showed the relationship between the stellar environment that the SNR resides and the type of SN that it underwent, allowing for this information to be use to better understand other galaxies and star forming regions. With a more complete luminosity function, it was seen that the influence of SNRs to the cosmic ray acceleration in a galaxy is very significant.

Date of Award	2015
Original language	English