Studying the brightest radio sources in the southern sky
- Authors: Sejake, Precious Katlego
- Date: 2022-04-06
- Subjects: Galaxies Formation , Galaxies Evolution , Active galaxies , Radio galaxies , Radio sources (Astronomy) , Southern sky (Astronomy)
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/455350 , vital:75423
- Description: Active Galactic Nuclei (AGN) are among the most remarkable and powerful extragalactic radio sources in the Universe. The study of AGN enables us to understand better the critical mechanisms leading to the launch of radio jets, and its link to the central engine. Radio jets are thought to impact their host galaxy by promoting or suppressing star formation. By studying AGN, we can better understand their formation, evolution, and environment. The host galaxy cross-identification is a crucial step to be carried out to build a multi-wavelength analysis of powerful radio sources; AGN. The GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) 4Jy (G4Jy) Sample comprises 1,863 of the powerful radio sources in the southern sky. However, 140 sources from the G4Jy Sample were followed-up with the Open Time on MeerKAT. Of these 140 sources, 126 had an ambiguous host galaxy, and 13 had an identified host galaxy; however, there were some discrepancies in the literature concerning the host galaxy. The host-galaxy identification of these sources is limited by the poor resolution of radio data at 25" to 45". This study aims to assess the radio morphology of these 140 sources and identify their host galaxy using the ⇠ 7” resolution images from MeerKAT in conjunction with datasets at other wavelengths. This analysis is carried out by visually inspecting the overlays. The overlays comprise radio contours from 150 MHz, 200 MHz, 843/1400 MHz and 1300 MHz overlaid on the mid-infrared image (3.4 μm). The MeerKAT images reveal sources with various radio morphologies. While most of the sources have radio morphology of typical symmetric lobes, 10 radio sources have head-tail morphology, 14 are wide-angle tail (WAT), and 5 have X-, S- /Z-shaped morphology. Overall, we find host galaxies for 70% of the sources in the sample, with the remainder comprising sources with ambiguous host galaxy (20.7%) and sources with a faint mid-infrared host galaxy (9.3%). These results highlight the importance of angular resolution and sensitivity for morphological classification and host galaxy cross-identification. , Thesis (MSc) -- Faculty of Science, Physics and Electronics, 2022
- Full Text:
- Date Issued: 2022-04-06
- Authors: Sejake, Precious Katlego
- Date: 2022-04-06
- Subjects: Galaxies Formation , Galaxies Evolution , Active galaxies , Radio galaxies , Radio sources (Astronomy) , Southern sky (Astronomy)
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/455350 , vital:75423
- Description: Active Galactic Nuclei (AGN) are among the most remarkable and powerful extragalactic radio sources in the Universe. The study of AGN enables us to understand better the critical mechanisms leading to the launch of radio jets, and its link to the central engine. Radio jets are thought to impact their host galaxy by promoting or suppressing star formation. By studying AGN, we can better understand their formation, evolution, and environment. The host galaxy cross-identification is a crucial step to be carried out to build a multi-wavelength analysis of powerful radio sources; AGN. The GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) 4Jy (G4Jy) Sample comprises 1,863 of the powerful radio sources in the southern sky. However, 140 sources from the G4Jy Sample were followed-up with the Open Time on MeerKAT. Of these 140 sources, 126 had an ambiguous host galaxy, and 13 had an identified host galaxy; however, there were some discrepancies in the literature concerning the host galaxy. The host-galaxy identification of these sources is limited by the poor resolution of radio data at 25" to 45". This study aims to assess the radio morphology of these 140 sources and identify their host galaxy using the ⇠ 7” resolution images from MeerKAT in conjunction with datasets at other wavelengths. This analysis is carried out by visually inspecting the overlays. The overlays comprise radio contours from 150 MHz, 200 MHz, 843/1400 MHz and 1300 MHz overlaid on the mid-infrared image (3.4 μm). The MeerKAT images reveal sources with various radio morphologies. While most of the sources have radio morphology of typical symmetric lobes, 10 radio sources have head-tail morphology, 14 are wide-angle tail (WAT), and 5 have X-, S- /Z-shaped morphology. Overall, we find host galaxies for 70% of the sources in the sample, with the remainder comprising sources with ambiguous host galaxy (20.7%) and sources with a faint mid-infrared host galaxy (9.3%). These results highlight the importance of angular resolution and sensitivity for morphological classification and host galaxy cross-identification. , Thesis (MSc) -- Faculty of Science, Physics and Electronics, 2022
- Full Text:
- Date Issued: 2022-04-06
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
An investigation into the decametric radio emission by the planet Jupiter
- Authors: Gruber, Georg M
- Date: 1967
- Subjects: Jupiter (Planet) , Radio astronomy , Radio sources (Astronomy)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5545 , http://hdl.handle.net/10962/d1013410
- Description: From introduction: Jupiter is the largest planet in the solar system. Its distance from the Sun is five times that of the Earth and its mass is nearly two and a half times that of all the other planets added together. Jupiter turns about its own axis rather rapidly, once in just under ten hours, and it completes one revolution about the Sun in just under twelve years. Thus Earth has to pass almost directly between the Sun and Jupiter once every thirteen months. When this happens Jupiter is said to be in "opposition", as its position is then opposite to that of the Sun, when viewed from Earth. Around this time the planet will be most favourably placed for observations, as it is at its closest to Earth and up in the sky for a large part of the night. During the day observations on radio frequencies are more difficult, as the Sun is a source of great interference. Besides being an emitter of thermal electromagnetic radiation, as one would expect, Jupiter also emits two kinds of non-thermal radiation, one in the decimetre wavelength range and the other in the decametre wavelength range. A large number of scientists have worked on the problems of decimetre and decametre radiation. This thesis deals with some aspects of decametre radiation.
- Full Text:
- Date Issued: 1967
- Authors: Gruber, Georg M
- Date: 1967
- Subjects: Jupiter (Planet) , Radio astronomy , Radio sources (Astronomy)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5545 , http://hdl.handle.net/10962/d1013410
- Description: From introduction: Jupiter is the largest planet in the solar system. Its distance from the Sun is five times that of the Earth and its mass is nearly two and a half times that of all the other planets added together. Jupiter turns about its own axis rather rapidly, once in just under ten hours, and it completes one revolution about the Sun in just under twelve years. Thus Earth has to pass almost directly between the Sun and Jupiter once every thirteen months. When this happens Jupiter is said to be in "opposition", as its position is then opposite to that of the Sun, when viewed from Earth. Around this time the planet will be most favourably placed for observations, as it is at its closest to Earth and up in the sky for a large part of the night. During the day observations on radio frequencies are more difficult, as the Sun is a source of great interference. Besides being an emitter of thermal electromagnetic radiation, as one would expect, Jupiter also emits two kinds of non-thermal radiation, one in the decimetre wavelength range and the other in the decametre wavelength range. A large number of scientists have worked on the problems of decimetre and decametre radiation. This thesis deals with some aspects of decametre radiation.
- Full Text:
- Date Issued: 1967
An investigation of the radio emission by the planet Jupiter on 18 Mc/s & 22 Mc/s
- Authors: Gruber, Georg Maria
- Date: 1963
- Subjects: Radio astronomy , Jupiter (Planet) -- Observations , Radio sources (Astronomy)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5524 , http://hdl.handle.net/10962/d1012113 , Radio astronomy , Jupiter (Planet) -- Observations , Radio sources (Astronomy)
- Description: This thesis describes the investigation carried out of the radio noise emitted by the planet Jupiter on 18 Mc/s and 22 Mc/s. Chapter I gives a brief introduction and outlines radioastronomical as well as astronomical ideas concerning Jupiter. A detailed survey of the research done to date including some of the hypotheses formulated by previous workers is presented in Chapter II . Chapter III deals with the apparatus used in this research. Two similar sets of apparatus were used. The aerials were folded dipoles. The signals were fed to the receiver, an R 206 , via a 300 ohm impedance line. To increase the gain an extra I -F. stage was included. This gave a gain of better than a 120 dB. To match the signals into the recorder a cathode follower was used. The operating procedure appears in the fourth chapter. The results obtained are discussed and tabulated at the end of the chapter. They agree with the findings made by previous workers, within the experimental limit. Histograms of the occurrence probability versus the revised System III coordinates are presented for each frequency and compared to previous ones. The final chapter contains the author ' s interpretation of the observed effects. A model based on a radiation analogous to the Cerenkov effect is found to be not inconsistent with the available data . Ending the chapter suggestions for further research are made.
- Full Text:
- Date Issued: 1963
- Authors: Gruber, Georg Maria
- Date: 1963
- Subjects: Radio astronomy , Jupiter (Planet) -- Observations , Radio sources (Astronomy)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5524 , http://hdl.handle.net/10962/d1012113 , Radio astronomy , Jupiter (Planet) -- Observations , Radio sources (Astronomy)
- Description: This thesis describes the investigation carried out of the radio noise emitted by the planet Jupiter on 18 Mc/s and 22 Mc/s. Chapter I gives a brief introduction and outlines radioastronomical as well as astronomical ideas concerning Jupiter. A detailed survey of the research done to date including some of the hypotheses formulated by previous workers is presented in Chapter II . Chapter III deals with the apparatus used in this research. Two similar sets of apparatus were used. The aerials were folded dipoles. The signals were fed to the receiver, an R 206 , via a 300 ohm impedance line. To increase the gain an extra I -F. stage was included. This gave a gain of better than a 120 dB. To match the signals into the recorder a cathode follower was used. The operating procedure appears in the fourth chapter. The results obtained are discussed and tabulated at the end of the chapter. They agree with the findings made by previous workers, within the experimental limit. Histograms of the occurrence probability versus the revised System III coordinates are presented for each frequency and compared to previous ones. The final chapter contains the author ' s interpretation of the observed effects. A model based on a radiation analogous to the Cerenkov effect is found to be not inconsistent with the available data . Ending the chapter suggestions for further research are made.
- Full Text:
- Date Issued: 1963
- «
- ‹
- 1
- ›
- »