New insights on classical radio galaxies from MeerKAT and uGMRT
- Authors: Legodi, Portia Potasi
- Date: 2025-04-03
- Subjects: Radio galaxies , MeerKAT , Giant Metrewave Radio Telescope , Radio sources (Astronomy) , Radio interferometers
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/479886 , vital:78376 , DOI 10.21504/10962/479886
- Description: The morphology of low and high-power sources has been the subject of a classification method for over four decades, leading to a comprehensive understanding of extragalactic radio sources. The morphological classification of radio galaxies is again a hot topic. This project aims to revisit the current classification scheme for classical radio galaxies and investigate the properties and origin of the new filamentary features which are becoming standard within and outside the radio lobes and which are suggestive of so far unexplored interactions between the radio plasma and the external medium. This thesis presents high-resolution and sensitivity studies of the nature of ten known radio galaxies: three FRIs (4C -03.43, 3C 403.1, 3C 198), three FRIIs (3C 105, 3C 227, 3C 445), tailed radio sources (CGCG046-067, NGC7503) and the FR0s (SDSS J 09157+1331, SDSS J 1120+0407). The total sample was selected from the 4C catalogue with well-defined criteria. To this aim, we are using the μJy sensitivity offered by the combination of uGMRT and MeerKAT in a frequency range from 500−1712 MHz. The radio images present several new morphological features in the radio emission at a ∼4′′ −10′′ angular resolution. Our radio maps validate the morphological classification. The sources exhibit remarkable features that raise new questions regarding the complex interaction between radio plasma emitted by host galaxies and the surrounding medium through which the jet propagates. The wealth of morphological details includes, for example, the detection of filaments in the emission from the lobes, the existence of diffuse emission beyond the hotspots, and multiple knot-like structures along the jet spine in some sources in the sample. Detailed descriptions of the overall radio structures are presented. We derived the equipartition parameters for each source in the sample, and after fitting their integrated spectrum, we estimated their global radiative ages. We find a broad range of radiative ages, i.e. 40.19−242.85 Myr. We derived in-band spectral index imaging for a few radio galaxies in the sample. This allowed us to make some preliminary considerations on the origin of the various radio features. , Thesis (PhD) -- Faculty of Science, Physics and Electronics, 2025
- Full Text:
- Date Issued: 2025-04-03
- Authors: Legodi, Portia Potasi
- Date: 2025-04-03
- Subjects: Radio galaxies , MeerKAT , Giant Metrewave Radio Telescope , Radio sources (Astronomy) , Radio interferometers
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/479886 , vital:78376 , DOI 10.21504/10962/479886
- Description: The morphology of low and high-power sources has been the subject of a classification method for over four decades, leading to a comprehensive understanding of extragalactic radio sources. The morphological classification of radio galaxies is again a hot topic. This project aims to revisit the current classification scheme for classical radio galaxies and investigate the properties and origin of the new filamentary features which are becoming standard within and outside the radio lobes and which are suggestive of so far unexplored interactions between the radio plasma and the external medium. This thesis presents high-resolution and sensitivity studies of the nature of ten known radio galaxies: three FRIs (4C -03.43, 3C 403.1, 3C 198), three FRIIs (3C 105, 3C 227, 3C 445), tailed radio sources (CGCG046-067, NGC7503) and the FR0s (SDSS J 09157+1331, SDSS J 1120+0407). The total sample was selected from the 4C catalogue with well-defined criteria. To this aim, we are using the μJy sensitivity offered by the combination of uGMRT and MeerKAT in a frequency range from 500−1712 MHz. The radio images present several new morphological features in the radio emission at a ∼4′′ −10′′ angular resolution. Our radio maps validate the morphological classification. The sources exhibit remarkable features that raise new questions regarding the complex interaction between radio plasma emitted by host galaxies and the surrounding medium through which the jet propagates. The wealth of morphological details includes, for example, the detection of filaments in the emission from the lobes, the existence of diffuse emission beyond the hotspots, and multiple knot-like structures along the jet spine in some sources in the sample. Detailed descriptions of the overall radio structures are presented. We derived the equipartition parameters for each source in the sample, and after fitting their integrated spectrum, we estimated their global radiative ages. We find a broad range of radiative ages, i.e. 40.19−242.85 Myr. We derived in-band spectral index imaging for a few radio galaxies in the sample. This allowed us to make some preliminary considerations on the origin of the various radio features. , Thesis (PhD) -- Faculty of Science, Physics and Electronics, 2025
- Full Text:
- Date Issued: 2025-04-03
Observations of diffuse radio emission in the Perseus Galaxy Cluster
- Authors: Mungwariri, Clemence
- Date: 2020
- Subjects: Galaxies -- Clusters , Radio sources (Astronomy) , Radio interferometers , Perseus Galaxy Cluster , Diffuse radio emission
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/143325 , vital:38233
- Description: In this thesis we analysed Westerbork observations of the Perseus Galaxy Cluster at 1380 MHz. Observations consist of two different pointings, covering a total of ∼ 0.5 square degrees, one including the known mini halo and the source 3C 84, the other centred on the source 3C 83.1 B. We obtained images with 83 μJy beam⁻¹ and 240 μJy beam⁻¹ noise rms for the two pointings respectively. We achieved a 60000 : 1 dynamic range in the image containing the bright 3C 84 source. We imaged the mini halo surrounding 3C 84 at high sensitivity, measuring its diameter to be ∼140 kpc and its power 4 x 10²⁴ W Hz⁻¹. Its morphology agrees quite well with that observed at 240 MHz (e.g. Gendron-Marsolais et al., 2017). We measured the flux density of 3C 84 to be 20.5 ± 0.4 Jy at the 2007 epoch, consistent with a factor of ∼2 increase since the 1960s.
- Full Text:
- Date Issued: 2020
- Authors: Mungwariri, Clemence
- Date: 2020
- Subjects: Galaxies -- Clusters , Radio sources (Astronomy) , Radio interferometers , Perseus Galaxy Cluster , Diffuse radio emission
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/143325 , vital:38233
- Description: In this thesis we analysed Westerbork observations of the Perseus Galaxy Cluster at 1380 MHz. Observations consist of two different pointings, covering a total of ∼ 0.5 square degrees, one including the known mini halo and the source 3C 84, the other centred on the source 3C 83.1 B. We obtained images with 83 μJy beam⁻¹ and 240 μJy beam⁻¹ noise rms for the two pointings respectively. We achieved a 60000 : 1 dynamic range in the image containing the bright 3C 84 source. We imaged the mini halo surrounding 3C 84 at high sensitivity, measuring its diameter to be ∼140 kpc and its power 4 x 10²⁴ W Hz⁻¹. Its morphology agrees quite well with that observed at 240 MHz (e.g. Gendron-Marsolais et al., 2017). We measured the flux density of 3C 84 to be 20.5 ± 0.4 Jy at the 2007 epoch, consistent with a factor of ∼2 increase since the 1960s.
- Full Text:
- Date Issued: 2020
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