Unraveling a cosmic phoenix: multi-wavelength exploration of Galactic Supernova Remnant G311.5-0.3

Abstract

This study is a multi-wavelength analysis into the heart of a single object: Galactic SNR G311.5–0.3. Data from radio, infrared, and high-energy 𝛾-ray observations is fused together to give insight into the physical processes that drive the SNR and its environment.

The first result is a high-resolution image, pieced together using radio data from the ATCA. This gives insight into the physical mechanism that is the source of its radio emission: non-thermal sycnchrotron radiation which is emitted by electrons spiralling around in the magnetic field. This portrayal provides a vivid visual narrative of the SNR’s extended structure. I constrain a new value for the spectral index of 𝛼 = −0.73 ± 0.02 in radio from a previously approximated value of 𝛼 ≈ −0.5 in the Green (2019) catalog for G311.5–0.3. This spectral index is found to be relatively steeper than the SNR population in galaxies of the Local Group, but still within the expected range of 0.5 – 1. From the radio image, a more accurate angular size of 4.4 arcmin (264′′) is calculated for the SNR which translates to a physical size of 17.3 pc, placing G311.5–0.3 among somewhat smaller SNRs than its Galactic counterparts. Further radio analysis allow the calculation of the strength of the magnetic field, luminosity and radio surface brightness, all of which are well within range for other SNRs in galaxies of the Local Group.

This thesis is an example of a multi-wavelength approach to study SNRs. The various properties of G311.5–0.3 that I put forth in this study are juxtaposed with other SNRs, offering a comparative analysis among the ensemble of its Galactic counterparts. Navigating through the spectrum of observations, the radio waves reveal it’s morphology, angular size, spectral index, surface brightness and luminosity. The infrared emission from WISE illuminates the remnants’ thermal glow, while the high-energy emissions detected by Fermi-LAT lend insight into the interactions of cosmic-rays with the magnetic fields. Coupled with the study of HI and CO, these analyses shed further light on a turbulent environment of G311.5–0.3, placing a new constraint on the distance. This allows understanding the remnant’s past and some speculation about its future evolution. Are the findings in this thesis cutting edge? Do they have a great impact? Perhaps not. But perhaps they serve as a stepping stone to study the deeper questions surrounding SNRs in the universe.

Date of Thesis submission	2023
Original language	English
Awarding Institution	Western Sydney University
Supervisor	Miroslav Filipovic (Supervisor) & Luke Barnes (Supervisor)