Extragalactic Peaked-spectrum Radio Sources at Low Frequencies
We present a sample of 1483 sources that display spectral peaks between 72 MHz and 1.4 GHz, selected from the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey. The GLEAM survey is the widest fractional bandwidth all-sky survey to date, ideal for identifying peaked-spectrum...
| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , |
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| Format: | Journal Article |
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Institute of Physics Publishing
2017
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| Online Access: | http://hdl.handle.net/20.500.11937/51477 |
| _version_ | 1848758707833274368 |
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| author | Callingham, J. Ekers, Ronald Gaensler, B. Line, J. Hurley-Walker, Natasha Sadler, E. Tingay, Steven Hancock, Paul Bell, M. Dwarakanath, K. For, B. Franzen, Thomas Hindson, L. Johnston-Hollitt, M. Kapinska, A. Lenc, E. McKinley, B. Morgan, J. Offringa, A. Procopio, P. Staveley-Smith, L. Wayth, Randall Wu, C. Zheng, Q. |
| author_facet | Callingham, J. Ekers, Ronald Gaensler, B. Line, J. Hurley-Walker, Natasha Sadler, E. Tingay, Steven Hancock, Paul Bell, M. Dwarakanath, K. For, B. Franzen, Thomas Hindson, L. Johnston-Hollitt, M. Kapinska, A. Lenc, E. McKinley, B. Morgan, J. Offringa, A. Procopio, P. Staveley-Smith, L. Wayth, Randall Wu, C. Zheng, Q. |
| author_sort | Callingham, J. |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | We present a sample of 1483 sources that display spectral peaks between 72 MHz and 1.4 GHz, selected from the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey. The GLEAM survey is the widest fractional bandwidth all-sky survey to date, ideal for identifying peaked-spectrum sources at low radio frequencies. Our peaked-spectrum sources are the low-frequency analogs of gigahertz-peaked spectrum (GPS) and compact-steep spectrum (CSS) sources, which have been hypothesized to be the precursors to massive radio galaxies. Our sample more than doubles the number of known peaked-spectrum candidates, and 95% of our sample have a newly characterized spectral peak. We highlight that some GPS sources peaking above 5 GHz have had multiple epochs of nuclear activity, and we demonstrate the possibility of identifying high-redshift (z > 2) galaxies via steep optically thin spectral indices and low observed peak frequencies. The distribution of the optically thick spectral indices of our sample is consistent with past GPS/CSS samples but with a large dispersion, suggesting that the spectral peak is a product of an inhomogeneous environment that is individualistic. We find no dependence of observed peak frequency with redshift, consistent with the peaked-spectrum sample comprising both local CSS sources and high-redshift GPS sources. The 5 GHz luminosity distribution lacks the brightest GPS and CSS sources of previous samples, implying that a convolution of source evolution and redshift influences the type of peaked-spectrum sources identified below 1 GHz. Finally, we discuss sources with optically thick spectral indices that exceed the synchrotron self-absorption limit. © 2017. The American Astronomical Society. All rights reserved. |
| first_indexed | 2025-11-14T09:48:16Z |
| format | Journal Article |
| id | curtin-20.500.11937-51477 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T09:48:16Z |
| publishDate | 2017 |
| publisher | Institute of Physics Publishing |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-514772018-03-05T09:02:37Z Extragalactic Peaked-spectrum Radio Sources at Low Frequencies Callingham, J. Ekers, Ronald Gaensler, B. Line, J. Hurley-Walker, Natasha Sadler, E. Tingay, Steven Hancock, Paul Bell, M. Dwarakanath, K. For, B. Franzen, Thomas Hindson, L. Johnston-Hollitt, M. Kapinska, A. Lenc, E. McKinley, B. Morgan, J. Offringa, A. Procopio, P. Staveley-Smith, L. Wayth, Randall Wu, C. Zheng, Q. We present a sample of 1483 sources that display spectral peaks between 72 MHz and 1.4 GHz, selected from the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey. The GLEAM survey is the widest fractional bandwidth all-sky survey to date, ideal for identifying peaked-spectrum sources at low radio frequencies. Our peaked-spectrum sources are the low-frequency analogs of gigahertz-peaked spectrum (GPS) and compact-steep spectrum (CSS) sources, which have been hypothesized to be the precursors to massive radio galaxies. Our sample more than doubles the number of known peaked-spectrum candidates, and 95% of our sample have a newly characterized spectral peak. We highlight that some GPS sources peaking above 5 GHz have had multiple epochs of nuclear activity, and we demonstrate the possibility of identifying high-redshift (z > 2) galaxies via steep optically thin spectral indices and low observed peak frequencies. The distribution of the optically thick spectral indices of our sample is consistent with past GPS/CSS samples but with a large dispersion, suggesting that the spectral peak is a product of an inhomogeneous environment that is individualistic. We find no dependence of observed peak frequency with redshift, consistent with the peaked-spectrum sample comprising both local CSS sources and high-redshift GPS sources. The 5 GHz luminosity distribution lacks the brightest GPS and CSS sources of previous samples, implying that a convolution of source evolution and redshift influences the type of peaked-spectrum sources identified below 1 GHz. Finally, we discuss sources with optically thick spectral indices that exceed the synchrotron self-absorption limit. © 2017. The American Astronomical Society. All rights reserved. 2017 Journal Article http://hdl.handle.net/20.500.11937/51477 10.3847/1538-4357/836/2/174 Institute of Physics Publishing fulltext |
| spellingShingle | Callingham, J. Ekers, Ronald Gaensler, B. Line, J. Hurley-Walker, Natasha Sadler, E. Tingay, Steven Hancock, Paul Bell, M. Dwarakanath, K. For, B. Franzen, Thomas Hindson, L. Johnston-Hollitt, M. Kapinska, A. Lenc, E. McKinley, B. Morgan, J. Offringa, A. Procopio, P. Staveley-Smith, L. Wayth, Randall Wu, C. Zheng, Q. Extragalactic Peaked-spectrum Radio Sources at Low Frequencies |
| title | Extragalactic Peaked-spectrum Radio Sources at Low Frequencies |
| title_full | Extragalactic Peaked-spectrum Radio Sources at Low Frequencies |
| title_fullStr | Extragalactic Peaked-spectrum Radio Sources at Low Frequencies |
| title_full_unstemmed | Extragalactic Peaked-spectrum Radio Sources at Low Frequencies |
| title_short | Extragalactic Peaked-spectrum Radio Sources at Low Frequencies |
| title_sort | extragalactic peaked-spectrum radio sources at low frequencies |
| url | http://hdl.handle.net/20.500.11937/51477 |