Remnant radio galaxies discovered in a multi-frequency survey
The remnant phase of a radio galaxy begins when the jets launched from an active galactic nucleus are switched off. To study the fraction of radio galaxies in a remnant phase, we take advantage of a deg subregion of the GAMA 23 field which comprises of surveys covering the frequency range 0.1-9 GHz....
| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , |
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| Format: | Journal Article |
| Language: | English |
| Published: |
CAMBRIDGE UNIV PRESS
2021
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| Subjects: | |
| Online Access: | http://purl.org/au-research/grants/arc/FT190100231 http://hdl.handle.net/20.500.11937/91778 |
| _version_ | 1848765589746614272 |
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| author | Quici, B. Hurley-Walker, Natasha Seymour, Nick Turner, Ross Shabala, S.S. Huynh, M. Andernach, H. Kapińska, A.D. Collier, J.D. Johnston-Hollitt, Melanie White, S.V. Prandoni, I. Galvin, Tim Franzen, Thomas Ishwara-Chandra, C.H. Bellstedt, S. Tingay, Steven Gaensler, B.M. O'Brien, A. Rogers, J. Chow, K. Driver, S. Robotham, A. |
| author_facet | Quici, B. Hurley-Walker, Natasha Seymour, Nick Turner, Ross Shabala, S.S. Huynh, M. Andernach, H. Kapińska, A.D. Collier, J.D. Johnston-Hollitt, Melanie White, S.V. Prandoni, I. Galvin, Tim Franzen, Thomas Ishwara-Chandra, C.H. Bellstedt, S. Tingay, Steven Gaensler, B.M. O'Brien, A. Rogers, J. Chow, K. Driver, S. Robotham, A. |
| author_sort | Quici, B. |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | The remnant phase of a radio galaxy begins when the jets launched from an active galactic nucleus are switched off. To study the fraction of radio galaxies in a remnant phase, we take advantage of a deg subregion of the GAMA 23 field which comprises of surveys covering the frequency range 0.1-9 GHz. We present a sample of 104 radio galaxies compiled from observations conducted by the Murchison Widefield Array (216 MHz), the Australia Square Kilometer Array Pathfinder (887 MHz), and the Australia Telescope Compact Array (5.5 GHz). We adopt an 'absent radio core' criterion to identify 10 radio galaxies showing no evidence for an active nucleus. We classify these as new candidate remnant radio galaxies. Seven of these objects still display compact emitting regions within the lobes at 5.5 GHz; at this frequency the emission is short-lived, implying a recent jet switch off. On the other hand, only three show evidence of aged lobe plasma by the presence of an ultra-steep-spectrum (<![CDATA[$\alpha) and a diffuse, low surface brightness radio morphology. The predominant fraction of young remnants is consistent with a rapid fading during the remnant phase. Within our sample of radio galaxies, our observations constrain the remnant fraction to; the lower limit comes from the limiting case in which all remnant candidates with hotspots are simply active radio galaxies with faint, undetected radio cores. Finally, we model the synchrotron spectrum arising from a hotspot to show they can persist for 5-10 Myr at 5.5 GHz after the jets switch of - radio emission arising from such hotspots can therefore be expected in an appreciable fraction of genuine remnants. |
| first_indexed | 2025-11-14T11:37:39Z |
| format | Journal Article |
| id | curtin-20.500.11937-91778 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| language | English |
| last_indexed | 2025-11-14T11:37:39Z |
| publishDate | 2021 |
| publisher | CAMBRIDGE UNIV PRESS |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-917782023-05-16T06:33:47Z Remnant radio galaxies discovered in a multi-frequency survey Quici, B. Hurley-Walker, Natasha Seymour, Nick Turner, Ross Shabala, S.S. Huynh, M. Andernach, H. Kapińska, A.D. Collier, J.D. Johnston-Hollitt, Melanie White, S.V. Prandoni, I. Galvin, Tim Franzen, Thomas Ishwara-Chandra, C.H. Bellstedt, S. Tingay, Steven Gaensler, B.M. O'Brien, A. Rogers, J. Chow, K. Driver, S. Robotham, A. Science & Technology Physical Sciences Astronomy & Astrophysics galaxies: active methods: statistical radio continuum: galaxies ARRAY EVOLUTION LUMINOSITY ENERGETICS EMISSION CLUSTERS NUCLEI MODELS LOBES AGN astro-ph.GA astro-ph.GA The remnant phase of a radio galaxy begins when the jets launched from an active galactic nucleus are switched off. To study the fraction of radio galaxies in a remnant phase, we take advantage of a deg subregion of the GAMA 23 field which comprises of surveys covering the frequency range 0.1-9 GHz. We present a sample of 104 radio galaxies compiled from observations conducted by the Murchison Widefield Array (216 MHz), the Australia Square Kilometer Array Pathfinder (887 MHz), and the Australia Telescope Compact Array (5.5 GHz). We adopt an 'absent radio core' criterion to identify 10 radio galaxies showing no evidence for an active nucleus. We classify these as new candidate remnant radio galaxies. Seven of these objects still display compact emitting regions within the lobes at 5.5 GHz; at this frequency the emission is short-lived, implying a recent jet switch off. On the other hand, only three show evidence of aged lobe plasma by the presence of an ultra-steep-spectrum (<![CDATA[$\alpha) and a diffuse, low surface brightness radio morphology. The predominant fraction of young remnants is consistent with a rapid fading during the remnant phase. Within our sample of radio galaxies, our observations constrain the remnant fraction to; the lower limit comes from the limiting case in which all remnant candidates with hotspots are simply active radio galaxies with faint, undetected radio cores. Finally, we model the synchrotron spectrum arising from a hotspot to show they can persist for 5-10 Myr at 5.5 GHz after the jets switch of - radio emission arising from such hotspots can therefore be expected in an appreciable fraction of genuine remnants. 2021 Journal Article http://hdl.handle.net/20.500.11937/91778 10.1017/pasa.2020.49 English http://purl.org/au-research/grants/arc/FT190100231 CAMBRIDGE UNIV PRESS fulltext |
| spellingShingle | Science & Technology Physical Sciences Astronomy & Astrophysics galaxies: active methods: statistical radio continuum: galaxies ARRAY EVOLUTION LUMINOSITY ENERGETICS EMISSION CLUSTERS NUCLEI MODELS LOBES AGN astro-ph.GA astro-ph.GA Quici, B. Hurley-Walker, Natasha Seymour, Nick Turner, Ross Shabala, S.S. Huynh, M. Andernach, H. Kapińska, A.D. Collier, J.D. Johnston-Hollitt, Melanie White, S.V. Prandoni, I. Galvin, Tim Franzen, Thomas Ishwara-Chandra, C.H. Bellstedt, S. Tingay, Steven Gaensler, B.M. O'Brien, A. Rogers, J. Chow, K. Driver, S. Robotham, A. Remnant radio galaxies discovered in a multi-frequency survey |
| title | Remnant radio galaxies discovered in a multi-frequency survey |
| title_full | Remnant radio galaxies discovered in a multi-frequency survey |
| title_fullStr | Remnant radio galaxies discovered in a multi-frequency survey |
| title_full_unstemmed | Remnant radio galaxies discovered in a multi-frequency survey |
| title_short | Remnant radio galaxies discovered in a multi-frequency survey |
| title_sort | remnant radio galaxies discovered in a multi-frequency survey |
| topic | Science & Technology Physical Sciences Astronomy & Astrophysics galaxies: active methods: statistical radio continuum: galaxies ARRAY EVOLUTION LUMINOSITY ENERGETICS EMISSION CLUSTERS NUCLEI MODELS LOBES AGN astro-ph.GA astro-ph.GA |
| url | http://purl.org/au-research/grants/arc/FT190100231 http://hdl.handle.net/20.500.11937/91778 |