University of Hertfordshire

From the same journal

From the same journal

Extragalactic Peaked-Spectrum Radio Sources at Low Frequencies

Research output: Contribution to journalArticlepeer-review

Documents

  • 1701.02771

    Accepted author manuscript, 2.98 MB, PDF document

Links

  • J. R. Callingham
  • R. D. Ekers
  • B. M. Gaensler
  • J. L. B. Line
  • N. Hurley-Walker
  • E. M. Sadler
  • S. J. Tingay
  • P. J. Hancock
  • M. E. Bell
  • K. S. Dwarakanath
  • B. -Q. For
  • T. M. O. Franzen
  • Luke Hindson
  • M. Johnston-Hollitt
  • A. D. Kapinska
  • E. Lenc
  • B. McKinley
  • J. Morgan
  • A. R. Offringa
  • P. Procopio
  • And 4 others
  • L. Staveley-Smith
  • R. B. Wayth
  • C. Wu
  • Q. Zheng
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Original languageEnglish
Number of pages28
JournalThe Astrophysical Journal
Volume836
Issue2
Early online date17 Feb 2017
DOIs
Publication statusPublished - 20 Feb 2017

Abstract

We present a sample of 1,483 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 analogues 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 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.

Notes

This document is the Accepted Manuscript of the following article: J.R. Callingham, et al, 'Extragalactic Peaked-Spectrum Radio Sources at Low Frequencies', The Astrophysical Journal, 836 (2), (28pp), first published online 17 February 2017. DOI: https://doi.org/10.3847/1538-4357-836/2/174. © 2017, The American Astronomical Society. All rights reserved. Data tables, and the appendix containing all of the SEDs, are available from the journal and on request to the author

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