Towards Gamma-Ray Telescopes in Australia
| dc.contributor.advisor | Einecke, Sabrina | |
| dc.contributor.advisor | Rowell, Gavin | |
| dc.contributor.author | Lee, Simon Alan Theodor | |
| dc.contributor.school | School of Physics, Chemistry and Earth Sciences | |
| dc.date.issued | 2024 | |
| dc.description.abstract | Recent decades have seen the rise of the field of gamma-ray astronomy, probing the most extreme environments in our Universe. The upcoming Cherenkov Telescope Array Observatory (CTAO), alongside H.E.S.S. in Namibia, are Imaging Air Cherenkov Telescopes (IACTs) that will cover roughly two thirds of the Southern Hemisphere gamma-ray sky. Short-term and variable events, or “transients”, in the Australian night sky would thus be unobservable. To this end, Monte Carlo simulations of hypothetical IACT arrays were created to determine and optimise the expected performance and scientific output of a potential Australian gamma-ray telescope. With the configurations used by CTAO as a base, a software pipeline was set up and configured for processing simulated telescope data, applying different methods of camera triggering and image cleaning, applying machine learning tools for reconstructing events, comparing array performance, and simulating observations of astronomical sources. Differential sensitivity, angular resolution, and effective area performance were compared between arrays of different altitudes (0m and 1000 m), numbers of telescopes (1 through 4), sizes of telescopes (using the “Small-” and “Medium-Sized Telescope” (SST & MST) designs from CTAO), and array baselines (from 80m to 277 m). To attempt to improve low-energy performance, a stereoscopic trigger (requiring multiple telescopes to detect an event), a topological trigger (requiring images to be in a limited region of the camera), and the combination of both were implemented and investigated. Additionally, a large collection of transient gamma-ray sources from the Fermi All-sky Variability Analysis catalogue were processed, simulated, and assessed for their detectability by an Australian IACT array. Across almost all energies, doubling the telescope count from one to two or two to four allowed for the detection of 2.5× dimmer sources. MSTs could detect gamma rays down to ∼200 GeV, whereas SSTs were restricted to energies above ∼1TeV. Above ∼3TeV, two SSTs had comparable sensitivity to one MST, and four SSTs were similar to two MSTs. Low-energy sensitivity was slightly improved at 1000m altitude compared to at 0 m. Angular resolution improved up to two-fold when increasing the baseline up to 277 m. Lowered image cleaning thresholds allowed for detection of ∼30-50% more active galactic nucleus (AGN) flares, with smaller improvements available from implementing a stereoscopic trigger for MST arrays, and a topological trigger for SSTs. An array of four MSTs was estimated to detect ∼24 AGN flares >5σ per year, up to a redshift of z ≈ 1.5. Two MSTs achieved ∼80–90% of the detections of four MSTs. The modelled Galactic transients were detectable within the observation time of one night, 11 of the 21 modelled gammaray bursts were detectable, as were ∼10% of unidentified transients. An array of MST-class telescopes in Australia would thus be a valuable complementary telescope array for transient TeV gamma-ray astronomy. | |
| dc.description.dissertation | Thesis (Ph.D.) -- University of Adelaide, School of Physics, Chemistry and Earth Sciences, 2024 | en |
| dc.identifier.uri | https://hdl.handle.net/2440/144196 | |
| dc.language.iso | en | |
| dc.provenance | This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exceptions. If you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at: http://www.adelaide.edu.au/legals | en |
| dc.title | Towards Gamma-Ray Telescopes in Australia | |
| dc.type | Thesis | en |
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