Radio spectra of bright compact sources at z > 4.5
High-redshift quasars are important to study galaxy and active galactic nuclei evolution, test cosmological models and study supermassive black hole growth. Optical searches for high-redshift sources have been very successful, but radio searches are not hampered by dust obscuration and should be mor...
| Main Authors: | , , , , , , , , , , , , |
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| Format: | Journal Article |
| Published: |
Oxford University Press
2017
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| Online Access: | http://hdl.handle.net/20.500.11937/74076 |
| _version_ | 1848763173815975936 |
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| author | Coppejans, R. van Velzen, S. Intema, Hubertus Müller, C. Frey, S. Coppejans, D. Cseh, D. Williams, W. Falcke, H. Körding, E. Orrú, E. Paragi, Z. Gabányi, K. |
| author_facet | Coppejans, R. van Velzen, S. Intema, Hubertus Müller, C. Frey, S. Coppejans, D. Cseh, D. Williams, W. Falcke, H. Körding, E. Orrú, E. Paragi, Z. Gabányi, K. |
| author_sort | Coppejans, R. |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | High-redshift quasars are important to study galaxy and active galactic nuclei evolution, test cosmological models and study supermassive black hole growth. Optical searches for high-redshift sources have been very successful, but radio searches are not hampered by dust obscuration and should be more effective at finding sources at even higher redshifts. Identifying high-redshift sources based on radio data is, however, not trivial. Here we report on newmultifrequency Giant MetrewaveRadio Telescope observations of eight z > 4.5 sources previously studied at high angular resolution with very long baseline interferometry (VLBI). Combining these observations with those from the literature, we construct broad-band radio spectra of all 30 z > 4.5 sources that have been observed with VLBI. In the sample we found flat, steep and peaked spectra in approximately equal proportions. Despite several selection effects, we conclude that the z > 4.5 VLBI (and likely also non-VLBI) sources have diverse spectra and that only about a quarter of the sources in the sample have flat spectra. Previously, the majority of high-redshift radio sources were identified based on their ultrasteep spectra. Recently, a new method has been proposed to identify these objects based on their megahertzpeaked spectra. No method would have identified more than 18 per cent of the high-redshift sources in this sample. More effective methods are necessary to reliably identify complete samples of high-redshift sources based on radio data. |
| first_indexed | 2025-11-14T10:59:15Z |
| format | Journal Article |
| id | curtin-20.500.11937-74076 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T10:59:15Z |
| publishDate | 2017 |
| publisher | Oxford University Press |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-740762019-03-13T01:49:00Z Radio spectra of bright compact sources at z > 4.5 Coppejans, R. van Velzen, S. Intema, Hubertus Müller, C. Frey, S. Coppejans, D. Cseh, D. Williams, W. Falcke, H. Körding, E. Orrú, E. Paragi, Z. Gabányi, K. High-redshift quasars are important to study galaxy and active galactic nuclei evolution, test cosmological models and study supermassive black hole growth. Optical searches for high-redshift sources have been very successful, but radio searches are not hampered by dust obscuration and should be more effective at finding sources at even higher redshifts. Identifying high-redshift sources based on radio data is, however, not trivial. Here we report on newmultifrequency Giant MetrewaveRadio Telescope observations of eight z > 4.5 sources previously studied at high angular resolution with very long baseline interferometry (VLBI). Combining these observations with those from the literature, we construct broad-band radio spectra of all 30 z > 4.5 sources that have been observed with VLBI. In the sample we found flat, steep and peaked spectra in approximately equal proportions. Despite several selection effects, we conclude that the z > 4.5 VLBI (and likely also non-VLBI) sources have diverse spectra and that only about a quarter of the sources in the sample have flat spectra. Previously, the majority of high-redshift radio sources were identified based on their ultrasteep spectra. Recently, a new method has been proposed to identify these objects based on their megahertzpeaked spectra. No method would have identified more than 18 per cent of the high-redshift sources in this sample. More effective methods are necessary to reliably identify complete samples of high-redshift sources based on radio data. 2017 Journal Article http://hdl.handle.net/20.500.11937/74076 10.1093/mnras/stx215 Oxford University Press fulltext |
| spellingShingle | Coppejans, R. van Velzen, S. Intema, Hubertus Müller, C. Frey, S. Coppejans, D. Cseh, D. Williams, W. Falcke, H. Körding, E. Orrú, E. Paragi, Z. Gabányi, K. Radio spectra of bright compact sources at z > 4.5 |
| title | Radio spectra of bright compact sources at z > 4.5 |
| title_full | Radio spectra of bright compact sources at z > 4.5 |
| title_fullStr | Radio spectra of bright compact sources at z > 4.5 |
| title_full_unstemmed | Radio spectra of bright compact sources at z > 4.5 |
| title_short | Radio spectra of bright compact sources at z > 4.5 |
| title_sort | radio spectra of bright compact sources at z > 4.5 |
| url | http://hdl.handle.net/20.500.11937/74076 |