The Missing Supernova Remnant Problem: Searching for Galactic Supernova Remnants with EMU & POSSUM

• Author / Creator

  Ball, Brianna D.

• Supernova remnants (SNRs) are an important part of the stellar feedback cycle that regulates star formation and influences the evolution of galaxies. They disperse the heavy elements formed in the cores of massive stars back into the interstellar medium,
  are responsible for forming and destroying large quantities of dust, and are believed to be the dominant source of Galactic cosmic rays. It is widely accepted that there is a significant discrepancy between the number of SNRs that have been discovered in our Galaxy and the number that models predict we should be able to detect at radio frequencies. This is often referred to as the “missing supernova remnant problem”. Most of the known Galactic SNR population has been observed in the radio and thus, discoveries of new Galactic SNRs have historically been driven by the development of more sophisticated radio telescopes. Improvements in the resolution and sensitivity of these telescopes allow us to detect smaller and/or fainter sources that likely would have been missed in previous surveys. Based on our current catalogues, the missing
  SNR population is believed to mostly consist of low surface brightness sources and sources located in regions with complex backgrounds and high concentrations of other Galactic radio sources, like HII regions. There may also be SNRs located at high latitudes that have been missed in previous surveys of the Galactic plane. In this thesis, we present pilot data from the EMU and POSSUM sky surveys, conducted using the Australian Square Kilometre Array Pathfinder (ASKAP). We use this pilot data as a test case to assess the capabilities of these surveys to uncover new SNR candidates and to develop techniques that can be used to search for and study SNRs with the full surveys as data become available. The results show remarkable success as we detect 21 SNR candidates in a field that previously only contained 7 known SNRs. If these candidates are confirmed, this will quadruple the number of SNRs in this small test field. By comparing our candidates to the known Galactic SNR population, we demonstrate that ASKAP should be capable of detecting many of the faint sources that likely comprise the majority of the missing SNR population. We believe that new SNRs discovered using these surveys will contribute to our understanding of the Galactic SNR population by allowing us to build a more complete census and conduct statistical studies of the distribution of SNRs in the Galaxy.

• Subjects / Keywords

  • Supernova remnants

• Graduation date

  Fall 2023

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-1794-zm78

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.