Mining MeerKAT data for minute to hour timescale transients and variable sources
- Authors: Gcilitshana, Sihle
- Date: 2024-10-11
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/464886 , vital:76554
- Description: In radio astronomy, minute-to-hour timescale transients and variable sources present an understudied population. We now have an unprecedented view of the transient radio sky due to the advent of new telescopes (such as the MeerKAT) with high instantaneous sensitivity, excellent snapshot imaging capabilities, and a large field of view. We can now probe into this population. This thesis presents the search for minute-to-hour timescale transient and variable sources in two of MeerKAT archival observations: the COSMOS and MACS J2140.2−2339 fields. The fields were observed for eight and five hours at the UHF band, respectively. We employed the PARROT transient and variable search pipeline currently being developed by the RATT group at Rhodes University. The pipeline’s input is a cross-calibrated measurement set, and its outputs are light curves extracted from all the sources in the restored image of the field. Using the light curves from the pipeline, we detected two variable sources in the COSMOS field, scintillating Active Galactic Nuclei (AGNs), which are most likely caused by the turbulent plasma in the interstellar medium. Due to persistent ionospheric diffraction, no variable sources were detected in the MACS J2140.2−2339 field, and no transients were detected in either field. The thesis also highlights areas where improvements to the PARROT pipeline can be implemented. , Thesis (MSc) -- Faculty of Science, Physics and Electronics, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Gcilitshana, Sihle
- Date: 2024-10-11
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/464886 , vital:76554
- Description: In radio astronomy, minute-to-hour timescale transients and variable sources present an understudied population. We now have an unprecedented view of the transient radio sky due to the advent of new telescopes (such as the MeerKAT) with high instantaneous sensitivity, excellent snapshot imaging capabilities, and a large field of view. We can now probe into this population. This thesis presents the search for minute-to-hour timescale transient and variable sources in two of MeerKAT archival observations: the COSMOS and MACS J2140.2−2339 fields. The fields were observed for eight and five hours at the UHF band, respectively. We employed the PARROT transient and variable search pipeline currently being developed by the RATT group at Rhodes University. The pipeline’s input is a cross-calibrated measurement set, and its outputs are light curves extracted from all the sources in the restored image of the field. Using the light curves from the pipeline, we detected two variable sources in the COSMOS field, scintillating Active Galactic Nuclei (AGNs), which are most likely caused by the turbulent plasma in the interstellar medium. Due to persistent ionospheric diffraction, no variable sources were detected in the MACS J2140.2−2339 field, and no transients were detected in either field. The thesis also highlights areas where improvements to the PARROT pipeline can be implemented. , Thesis (MSc) -- Faculty of Science, Physics and Electronics, 2024
- Full Text:
- Date Issued: 2024-10-11
SolarKAT: a solar imaging pipeline for MeerKAT
- Samboco, Victória da Graça Gilberto
- Authors: Samboco, Victória da Graça Gilberto
- Date: 2024-10-11
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/465102 , vital:76573
- Description: Solar interference poses a significant challenge in radio interferometric observations, particularly with the increasing sensitivity of modern new-generation telescopes. This thesis presents the SolarKAT pipeline, a novel approach designed to mitigate solar interference in MeerKAT observations. The pipeline incorporates a series of steps, including self-calibration (second generation calibration or 2GC), precise determination of the Sun’s position, phase centre adjustments, creation of region-based masks, deconvolution, prediction, solar model subtraction, and peeling. We applied the SolarKAT pipeline to three datasets that feature the Sun in different conditions (frequency band and angular distance from the Sun to the telescope pointing position). These observations were obtained from three MeerKAT telescope surveys: ThunderKAT, MIGHTEE and LADUMA. We compared the visual images, peak fluxes, flux density, RMS and pixel distribution to evaluate the pipeline. Our results showed a notable reduction in solar interference. This is evidenced by the improved image quality, reduction in RMS and pixel distribution values, and consistent peak flux measurements after applying the pipeline. SolarKAT has not only improved the data quality but also demonstrated to be a valuable tool in producing high-quality solar images, which can be a helpful resource for solar physics and space weather forecasts. This study showcases the potential of the SolarKAT pipeline in enabling high-quality radio interferometric observations, even in the presence of solar interference. Unlike conventional methods that often discard corrupted visibilities (e.g. flagging), our approach focuses on recovering them. Additionally, the SolarKAT pipeline naturally delivers detailed images of the Sun. Our findings contribute to advancing the field of radio interferometry, providing a valuable tool for researchers seeking to enhance the accuracy of their observations and conduct studies in solar physics and space weather. , Thesis (MSc) -- Faculty of Science, Physics and Electronics, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Samboco, Victória da Graça Gilberto
- Date: 2024-10-11
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/465102 , vital:76573
- Description: Solar interference poses a significant challenge in radio interferometric observations, particularly with the increasing sensitivity of modern new-generation telescopes. This thesis presents the SolarKAT pipeline, a novel approach designed to mitigate solar interference in MeerKAT observations. The pipeline incorporates a series of steps, including self-calibration (second generation calibration or 2GC), precise determination of the Sun’s position, phase centre adjustments, creation of region-based masks, deconvolution, prediction, solar model subtraction, and peeling. We applied the SolarKAT pipeline to three datasets that feature the Sun in different conditions (frequency band and angular distance from the Sun to the telescope pointing position). These observations were obtained from three MeerKAT telescope surveys: ThunderKAT, MIGHTEE and LADUMA. We compared the visual images, peak fluxes, flux density, RMS and pixel distribution to evaluate the pipeline. Our results showed a notable reduction in solar interference. This is evidenced by the improved image quality, reduction in RMS and pixel distribution values, and consistent peak flux measurements after applying the pipeline. SolarKAT has not only improved the data quality but also demonstrated to be a valuable tool in producing high-quality solar images, which can be a helpful resource for solar physics and space weather forecasts. This study showcases the potential of the SolarKAT pipeline in enabling high-quality radio interferometric observations, even in the presence of solar interference. Unlike conventional methods that often discard corrupted visibilities (e.g. flagging), our approach focuses on recovering them. Additionally, the SolarKAT pipeline naturally delivers detailed images of the Sun. Our findings contribute to advancing the field of radio interferometry, providing a valuable tool for researchers seeking to enhance the accuracy of their observations and conduct studies in solar physics and space weather. , Thesis (MSc) -- Faculty of Science, Physics and Electronics, 2024
- Full Text:
- Date Issued: 2024-10-11
Discovery and classification of compact radio sources in the MeerKAT Galactic Centre data
- Authors: Rammala, Isabella Dineo
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432218 , vital:72852
- Description: Access restricted. Expected release date in 2025. , Thesis (PhD) -- Faculty of Science, Physics and Electronics, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Rammala, Isabella Dineo
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432218 , vital:72852
- Description: Access restricted. Expected release date in 2025. , Thesis (PhD) -- Faculty of Science, Physics and Electronics, 2023
- Full Text:
- Date Issued: 2023-10-13
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