Extragalactic Peaked-spectrum Radio Sources at Low Frequencies
MetadataShow full item record
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.
Copyright © 2017 The American Astronomical Society. All rights reserved.
Showing items related by title, author, creator and subject.
Sadler, E.; Ekers, Ronald; Mahony, E.; Mauch, T.; Murphy, T. (2014)We have made the first detailed study of the high-frequency radio-source population in the local Universe, using a sample of 202 radio sources from the Australia Telescope 20 GHz (AT20G) survey identified with galaxies ...
Herzog, A.; Norris, R.; Middelberg, E.; Seymour, Nick; Spitler, L.; Emonts, B.; Franzen, T.; Hunstead, R.; Intema, H.; Marvil, J.; Parker, Q.; Sirothia, S.; Hurley-Walker, Natasha; Bell, M.; Bernardi, G.; Bowman, J.; Briggs, F.; Cappallo, R.; Callingham, J.; Deshpande, A.; Dwarakanath, K.; For, B.; Greenhill, L.; Hancock, Paul; Hazelton, B.; Hindson, L.; Johnston-Hollitt, M.; Kapińska, A.; Kaplan, D.; Lenc, E.; Lonsdale, C.; McKinley, B.; McWhirter, S.; Mitchell, D.; Morales, M.; Morgan, E.; Morgan, J.; Oberoi, D.; Offringa, A.; Ord, S.; Prabu, T.; Procopio, P.; Udaya Shankar, N.; Srivani, K.; Staveley-Smith, L.; Subrahmanyan, R.; Tingay, Steven; Wayth, Randall; Webster, R.; Williams, A.; Williams, C.; Wu, C.; Zheng, Q.; Bannister, K.; Chippendale, A.; Harvey-Smith, L.; Heywood, I.; Indermuehle, B.; Popping, A.; Sault, R.; Whiting, M. (2016)Context: Infrared-faint radio sources (IFRS) are a class of radio-loud (RL) active galactic nuclei (AGN) at high redshifts (z 1:7) that are characterised by their relative infrared faintness, resulting in enormous ...
Hancock, Paul (2009)The Australia Telescope 20 GHz (AT20G) survey was used to select a complete sample of 656 Gigahertz Peaked Spectrum (GPS) sources with spectral turnovers above 5 GHz. The AT20G has near simultaneous observations at 4.8, ...