Utilizza questo identificativo per citare o creare un link a questo documento:
http://hdl.handle.net/20.500.12386/23473
Campo DC | Valore | Lingua |
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dc.contributor.author | Tingay, S. J. | en_US |
dc.contributor.author | Macquart, J. -P. | en_US |
dc.contributor.author | Collier, J. D. | en_US |
dc.contributor.author | Rees, G. | en_US |
dc.contributor.author | Callingham, J. R. | en_US |
dc.contributor.author | Stevens, J. | en_US |
dc.contributor.author | CARRETTI, ETTORE | en_US |
dc.contributor.author | Wayth, R. B. | en_US |
dc.contributor.author | Wong, G. F. | en_US |
dc.contributor.author | Trott, C. M. | en_US |
dc.contributor.author | McKinley, B. | en_US |
dc.contributor.author | BERNARDI, GIANNI | en_US |
dc.contributor.author | Bowman, J. D. | en_US |
dc.contributor.author | Briggs, F. | en_US |
dc.contributor.author | Cappallo, R. J. | en_US |
dc.contributor.author | Corey, B. E. | en_US |
dc.contributor.author | Deshpande, A. A. | en_US |
dc.contributor.author | Emrich, D. | en_US |
dc.contributor.author | Gaensler, B. M. | en_US |
dc.contributor.author | Goeke, R. | en_US |
dc.contributor.author | Greenhill, L. J. | en_US |
dc.contributor.author | Hazelton, B. J. | en_US |
dc.contributor.author | Johnston-Hollitt, M. | en_US |
dc.contributor.author | Kaplan, D. L. | en_US |
dc.contributor.author | Kasper, J. C. | en_US |
dc.contributor.author | Kratzenberg, E. | en_US |
dc.contributor.author | Lonsdale, C. J. | en_US |
dc.contributor.author | Lynch, M. J. | en_US |
dc.contributor.author | McWhirter, S. R. | en_US |
dc.contributor.author | Mitchell, D. A. | en_US |
dc.contributor.author | Morales, M. F. | en_US |
dc.contributor.author | Morgan, E. | en_US |
dc.contributor.author | Oberoi, D. | en_US |
dc.contributor.author | Ord, S. M. | en_US |
dc.contributor.author | Prabu, T. | en_US |
dc.contributor.author | Rogers, A. E. E. | en_US |
dc.contributor.author | Roshi, A. | en_US |
dc.contributor.author | Udaya Shankar, N. | en_US |
dc.contributor.author | Srivani, K. S. | en_US |
dc.contributor.author | Subrahmanyan, R. | en_US |
dc.contributor.author | Waterson, M. | en_US |
dc.contributor.author | Webster, R. L. | en_US |
dc.contributor.author | Whitney, A. R. | en_US |
dc.contributor.author | Williams, A. | en_US |
dc.contributor.author | Williams, C. L. | en_US |
dc.date.accessioned | 2020-03-23T16:09:37Z | - |
dc.date.available | 2020-03-23T16:09:37Z | - |
dc.date.issued | 2015 | en_US |
dc.identifier.issn | 0004-6256 | en_US |
dc.identifier.uri | http://hdl.handle.net/20.500.12386/23473 | - |
dc.description | This scientific work makes use of the Murchison Radio-astronomy Observatory, operated by the Commonwealth Scientific and Industrial Research Organisation (CSIRO). We acknowledge the Wajarri Yamatji people as the traditional owners of the Observatory site. Support for the MWA comes from the U.S. National Science Foundation (grants AST-0457585, PHY-0835713, CAREER-0847753, and AST-0908884), the Australian Research Council (LIEF grants LE0775621 and LE0882938), the U.S. Air Force Office of Scientific Research (grant FA9550-0510247), and the Centre for All-sky Astrophysics (an Australian Research Council Centre of Excellence funded by grant CE110001020). Support is also provided by the Smithsonian Astrophysical Observatory, the MIT School of Science, the Raman Research Institute, the Australian National University, and the Victoria University of Wellington (via grant MED-E1799 from the New Zealand Ministry of Economic Development and an IBM Shared University Research Grant). The Australian Federal government provides additional support via the CSIRO, National Collaborative Research Infrastructure Strategy, Education Investment Fund, the Australia India Strategic Research Fund, and Astronomy Australia Limited, under contract to Curtin University. We acknowledge the iVEC Petabyte Data Store, the Initiative in Innovative Computing and the CUDA Center for Excellence sponsored by NVIDIA at Harvard University, and the International Centre for Radio Astronomy Research (ICRAR), a Joint Venture of Curtin University and The University of Western Australia, funded by the Western Australian State government. SJT acknowledges support from the Western Australian Government via a Premier's Research Fellowship. The Australia Telescope Compact Array is part of the Australia Telescope National Facility which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO. The Parkes Radio Telescope is part of the Australia Telescope National Facility which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO. Facilities: ATCA, MWA, Parkes. | - |
dc.description.abstract | Using the new wideband capabilities of the ATCA, we obtain spectra for PKS 1718-649, a well-known gigahertz-peaked spectrum radio source. The observations, between approximately 1 and 10 GHz over 3 epochs spanning approximately 21 months, reveal variability both above the spectral peak at ̃3 GHz and below the peak. The combination of the low- and high-frequency variability cannot be easily explained using a single absorption mechanism, such as free-free absorption or synchrotron self-absorption. We find that the PKS 1718-649 spectrum and its variability are best explained by variations in the free-free optical depth on our line of sight to the radio source at low frequencies (below the spectral peak) and the adiabatic expansion of the radio source itself at high frequencies (above the spectral peak). The optical depth variations are found to be plausible when X-ray continuum absorption variability seen in samples of active galactic nuclei is considered. We find that the cause of the peaked spectrum in PKS 1718-649 is most likely due to free-free absorption. In agreement with previous studies, we find that the spectrum at each epoch of observation is best fit by a free-free absorption model characterized by a power-law distribution of free-free absorbing clouds. This agreement is extended to frequencies below the 1 GHz lower limit of the ATCA by considering new observations with Parkes at 725 MHz and 199 MHz observations with the newly operational Murchison Widefield Array. These lower frequency observations argue against families of absorption models (both free-free and synchrotron self-absorption) that are based on simple homogenous structures. | en_US |
dc.language.iso | eng | en_US |
dc.title | The Spectral Variability of the GHz-Peaked Spectrum Radio Source PKS 1718-649 and a Comparison of Absorption Models | en_US |
dc.type | Article | - |
dc.identifier.doi | 10.1088/0004-6256/149/2/74 | en_US |
dc.identifier.scopus | 2-s2.0-84922422672 | en_US |
dc.identifier.isi | 000349360200039 | en_US |
dc.identifier.url | https://iopscience.iop.org/article/10.1088/0004-6256/149/2/74 | en_US |
dc.relation.medium | STAMPA | en_US |
dc.relation.volume | 149 | en_US |
dc.relation.issue | 2 | en_US |
dc.relation.firstpage | 74 | en_US |
dc.type.referee | REF_1 | en_US |
dc.description.note | Article publisher page https://iopscience.iop.org/article/10.1088/0004-6256/149/2/74 | en_US |
dc.description.international | sì | en_US |
dc.relation.scientificsector | FIS/05 - ASTRONOMIA E ASTROFISICA | en_US |
dc.relation.journal | THE ASTRONOMICAL JOURNAL | en_US |
dc.type.miur | 262 Articolo in rivista | - |
dc.identifier.adsbibcode | 2015AJ....149...74T | en_US |
dc.relation.ercsector | Scienze Fisiche Settori ERC (ERC) di riferimento::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation | en_US |
dc.description.apc | no | en_US |
dc.description.oa | 1 – prodotto con file in versione Open Access (allegherò il file al passo 5-Carica) | en_US |
item.openairecristype | http://purl.org/coar/resource_type/c_18cf | - |
item.fulltext | With Fulltext | - |
item.grantfulltext | open | - |
item.languageiso639-1 | en | - |
item.openairetype | Article | - |
item.cerifentitytype | Publications | - |
crisitem.journal.journalissn | 0004-6256 | - |
crisitem.journal.ance | E016224 | - |
crisitem.author.dept | IRA Bologna | - |
crisitem.author.dept | IRA Bologna | - |
crisitem.author.orcid | 0000-0002-3973-8403 | - |
crisitem.author.orcid | 0000-0002-0916-7443 | - |
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