LOFAR VLBI studies at 55 MHz of 4C 43.15, a z = 2.4 radio galaxy
The correlation between radio spectral index and redshift has been exploited to discover high-redshift radio galaxies, but its underlying cause is unclear. It is crucial to characterize the particle acceleration and loss mechanisms in high-redshift radio galaxies to understand why their radio spectr...
| Main Authors: | , , , , , , , , , , |
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| Format: | Journal article |
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Oxford University Press
2016
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| _version_ | 1826273039902310400 |
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| author | Morabito, L Deller, A Röttgering, H Miley, G Varenius, E Shimwell, T Moldón, J Jackson, N Morganti, R van Weeren, R Oonk, J |
| author_facet | Morabito, L Deller, A Röttgering, H Miley, G Varenius, E Shimwell, T Moldón, J Jackson, N Morganti, R van Weeren, R Oonk, J |
| author_sort | Morabito, L |
| collection | OXFORD |
| description | The correlation between radio spectral index and redshift has been exploited to discover high-redshift radio galaxies, but its underlying cause is unclear. It is crucial to characterize the particle acceleration and loss mechanisms in high-redshift radio galaxies to understand why their radio spectral indices are steeper than their local counterparts. Low-frequency information on scales of ∼1 arcsec are necessary to determine the internal spectral index variation. In this paper we present the first spatially resolved studies at frequencies below 100 MHz of the z = 2.4 radio galaxy 4C 43.15 which was selected based on its ultrasteep spectral index (α < −1; Sν ∼ να) between 365 MHz and 1.4 GHz. Using the International Low Frequency Array Low Band Antenna we achieve subarcsecond imaging resolution at 55 MHz with very long baseline interferometry techniques. Our study reveals low-frequency radio emission extended along the jet axis, which connects the two lobes. The integrated spectral index for frequencies <500 MHz is −0.83. The lobes have integrated spectral indices of −1.31 ± 0.03 and −1.75 ± 0.01 for frequencies ≥1.4 GHz, implying a break frequency between 500 MHz and 1.4 GHz. These spectral properties are similar to those of local radio galaxies. We conclude that the initially measured ultrasteep spectral index is due to a combination of the steepening spectrum at high frequencies with a break at intermediate frequencies. |
| first_indexed | 2024-03-06T22:22:06Z |
| format | Journal article |
| id | oxford-uuid:5566548d-af9a-4916-8d2f-f7431f3346ac |
| institution | University of Oxford |
| last_indexed | 2024-03-06T22:22:06Z |
| publishDate | 2016 |
| publisher | Oxford University Press |
| record_format | dspace |
| spelling | oxford-uuid:5566548d-af9a-4916-8d2f-f7431f3346ac2022-03-26T16:43:45ZLOFAR VLBI studies at 55 MHz of 4C 43.15, a z = 2.4 radio galaxyJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:5566548d-af9a-4916-8d2f-f7431f3346acSymplectic Elements at OxfordOxford University Press2016Morabito, LDeller, ARöttgering, HMiley, GVarenius, EShimwell, TMoldón, JJackson, NMorganti, Rvan Weeren, ROonk, JThe correlation between radio spectral index and redshift has been exploited to discover high-redshift radio galaxies, but its underlying cause is unclear. It is crucial to characterize the particle acceleration and loss mechanisms in high-redshift radio galaxies to understand why their radio spectral indices are steeper than their local counterparts. Low-frequency information on scales of ∼1 arcsec are necessary to determine the internal spectral index variation. In this paper we present the first spatially resolved studies at frequencies below 100 MHz of the z = 2.4 radio galaxy 4C 43.15 which was selected based on its ultrasteep spectral index (α < −1; Sν ∼ να) between 365 MHz and 1.4 GHz. Using the International Low Frequency Array Low Band Antenna we achieve subarcsecond imaging resolution at 55 MHz with very long baseline interferometry techniques. Our study reveals low-frequency radio emission extended along the jet axis, which connects the two lobes. The integrated spectral index for frequencies <500 MHz is −0.83. The lobes have integrated spectral indices of −1.31 ± 0.03 and −1.75 ± 0.01 for frequencies ≥1.4 GHz, implying a break frequency between 500 MHz and 1.4 GHz. These spectral properties are similar to those of local radio galaxies. We conclude that the initially measured ultrasteep spectral index is due to a combination of the steepening spectrum at high frequencies with a break at intermediate frequencies. |
| spellingShingle | Morabito, L Deller, A Röttgering, H Miley, G Varenius, E Shimwell, T Moldón, J Jackson, N Morganti, R van Weeren, R Oonk, J LOFAR VLBI studies at 55 MHz of 4C 43.15, a z = 2.4 radio galaxy |
| title | LOFAR VLBI studies at 55 MHz of 4C 43.15, a z = 2.4 radio galaxy |
| title_full | LOFAR VLBI studies at 55 MHz of 4C 43.15, a z = 2.4 radio galaxy |
| title_fullStr | LOFAR VLBI studies at 55 MHz of 4C 43.15, a z = 2.4 radio galaxy |
| title_full_unstemmed | LOFAR VLBI studies at 55 MHz of 4C 43.15, a z = 2.4 radio galaxy |
| title_short | LOFAR VLBI studies at 55 MHz of 4C 43.15, a z = 2.4 radio galaxy |
| title_sort | lofar vlbi studies at 55 mhz of 4c 43 15 a z 2 4 radio galaxy |
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