Details

Autor(en) / Beteiligte

• Callingham, J. R.
• Ekers, R. D.
• Gaensler, B. M.
• Line, J. L. B.
• Hurley-Walker, N.
• Sadler, E. M.
• Tingay, S. J.
• Hancock, P. J.
• Bell, M. E.
• Dwarakanath, K. S.
• For, B.-Q.
• Franzen, T. M. O.
• Hindson, L.
• Johnston-Hollitt, M.
• Kapi ska, A. D.
• Lenc, E.
• McKinley, B.
• Morgan, J.
• Offringa, A. R.
• Procopio, P.
• Staveley-Smith, L.
• Wayth, R. B.
• Wu, C.
• Zheng, Q.

Titel

Extragalactic Peaked-spectrum Radio Sources at Low Frequencies

Ist Teil von

• The Astrophysical journal, 2017-02, Vol.836 (2), p.174

Ort / Verlag

Philadelphia: The American Astronomical Society

Erscheinungsjahr

2017

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• 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.