Please use this identifier to cite or link to this item:
http://hdl.handle.net/2289/6697
Title: | Extragalactic peaked-spectrum radio sources at low frequencies |
Authors: | Callingham, J.R. Ekers, R.D. Gaensler, B.M. Dwarakanath, K.S. +20 Co-authors |
Issue Date: | 20-Feb-2017 |
Publisher: | IOP Sciences for The American Astronomical Society |
Citation: | The Astrophysical Journal, 2017, Vol.836, p174 |
Abstract: | 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. |
Description: | Open Access |
URI: | http://hdl.handle.net/2289/6697 |
ISSN: | 0004-637X 1538-4357-(Online) |
Alternative Location: | http://adsabs.harvard.edu/abs/2017ApJ...836..174C https://arxiv.org/abs/1701.02771 http://dx.doi.org/10.3847/1538-4357/836/2/174 |
Copyright: | 2017, The American Astronomical Society. |
Appears in Collections: | Research Papers (A&A) |
Files in This Item:
File | Description | Size | Format | |
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2017_AstrophyJournal_836_174.pdf | Open Access | 3.14 MB | Adobe PDF | View/Open |
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