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Please use this identifier to cite or link to this item: http://hdl.handle.net/2289/6376
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dc.contributor.authorCallingham, J.R.-
dc.contributor.authorDeshpande, A.A.-
dc.contributor.authorPrabu, T.-
dc.contributor.authorSrivani, K.S.-
dc.contributor.authorSubrahmanyan, Ravi-
dc.contributor.authorUdaya Shankar, N.-
dc.contributor.author+22 Co-authors-
dc.date.accessioned2016-01-28T06:48:37Z-
dc.date.available2016-01-28T06:48:37Z-
dc.date.issued2015-08-
dc.identifier.citationThe Astrophysical Journal, 2015, Vol.809, p168en_US
dc.identifier.issn0004-637X-
dc.identifier.issn1538-4357-(Online)-
dc.identifier.urihttp://hdl.handle.net/2289/6376-
dc.descriptionRestricted Access. An open-access version is available at arXiv.org (one of the alternative locations)en_US
dc.description.abstractWe present broadband observations and spectral modeling of PKS B0008-421 and identify it as an extreme gigahertz-peaked spectrum (GPS) source. PKS B0008-421 is characterized by the steepest known spectral slope below the turnover, close to the theoretical limit of synchrotron self-absorption, and the smallest known spectral width of any GPS source. Spectral coverage of the source spans from 0.118 to 22 GHz, which includes data from the Murchison Widefield Array and the wide bandpass receivers on the Australia Telescope Compact Array. We have implemented a Bayesian inference model fitting routine to fit the data with internal free–free absorption (FFA), single- and double-component FFA in an external homogeneous medium, FFA in an external inhomogeneous medium, or single- and double-component synchrotron self-absorption models, all with and without a high-frequency exponential break. We find that without the inclusion of a high-frequency break these models cannot accurately fit the data, with significant deviations above and below the peak in the radio spectrum. The addition of a high-frequency break provides acceptable spectral fits for the inhomogeneous FFA and double-component synchrotron self-absorption models, with the inhomogeneous FFA model statistically favored. The requirement of a high-frequency spectral break implies that the source has ceased injecting fresh particles. Additional support for the inhomogeneous FFA model as being responsible for the turnover in the spectrum is given by the consistency between the physical parameters derived from the model fit and the implications of the exponential spectral break, such as the necessity of the source being surrounded by a dense ambient medium to maintain the peak frequency near the gigahertz region. This implies that PKS B0008-421 should display an internal H i column density greater than 1020 cm−2. The discovery of PKS B0008-421 suggests that the next generation of low radio frequency surveys could reveal a large population of GPS sources that have ceased activity, and that a portion of the ultra–steep-spectrum source population could be composed of these GPS sources in a relic phase.en_US
dc.language.isoenen_US
dc.publisherIOP Sciences for The American Astronomical Societyen_US
dc.relation.urihttp://adsabs.harvard.edu/abs/2015ApJ...809..168Cen_US
dc.relation.urihttp://arxiv.org/abs/1507.04819en_US
dc.relation.urihttp://dx.doi.org/10.1088/0004-637X/809/2/168en_US
dc.rights2015 American Astronomical Societyen_US
dc.subjectradiation mechanisms:en_US
dc.titleBroadband spectral modeling of the extreme gigahertz-peaked spectrum radio source PKS B0008-421en_US
dc.typeArticleen_US
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