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G J White - One of the best experts on this subject based on the ideXlab platform.
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agn duty cycle estimates for the ultra steep spectrum radio relic vlss j1431 8 1331
Astronomy and Astrophysics, 2015Co-Authors: A Shulevski, R Morganti, Peter Barthel, J J Harwood, G Brunetti, R J Van Weeren, Huub Rottgering, G J WhiteAbstract:Context. Steep spectrum radio Sources associated with active galactic nuclei (AGN) may contain remnants of past AGN activity episodes. Studying these Sources gives us insight into the AGN activity history. Novel instruments like the LOw Frequency ARray (LOFAR) are enabling studies of these fascinating structures to be made at tens to hundreds of MHz with sufficient resolution to analyse their complex morphology. Aims. Our goal is to characterize the integrated and resolved spectral properties of VESS J1431+1331 and estimate Source ages based on synchrotron radio emission models, thus putting constraints on the AGN duty cycle. Methods. Using a broad spectral coverage, we have derived spectral and curvature maps, and used synchrotron ageing models to determine the time elapsed from the last time the Source plasma was energized. We used LOFAR, Giant Metrewave Radio Telescope (GMRT) and Jansky Very Large Array (VLA) data. Results. We confirm the morphology and the spectral index values found in previous studies of this object. Based on our ageing analysis, we infer that the AGN that created this Source currently has very low levels of activity or that it is switched off. The derived ages for the larger Source Component range from around 60 to 130 Myr, hinting that the AGN activity decreased or stopped around 60 Myr ago. We observe that the area around the faint radio core located in the larger Source Component is the youngest, while the overall age of the smaller Source Component shows it to be the oldest part of the Source. Conclusions. Our analysis suggests that VLSS J1431.8+1331 is an intriguing, two-Component Source. The larger Component seems to host a faint radio core, suggesting that the Source may be an AGN radio relic. The spectral index we observe from the smaller Component is distinctly flatter at lower frequencies than the spectral index of the larger Component, suggesting the possibility that the smaller Component may be a shocked plasma bubble. From. the integrated Source spectrum, we deduce that its shape and slope can be used as tracers of the activity history of this type of steep spectrum radio Source. We discuss the implications this conclusion has for future studies of radio Sources having similar characteristics.
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agn duty cycle estimates for the ultra steep spectrum radio relic vlss j1431 8 1331
arXiv: Astrophysics of Galaxies, 2015Co-Authors: A Shulevski, R Morganti, Peter Barthel, J J Harwood, G Brunetti, R J Van Weeren, Huub Rottgering, G J WhiteAbstract:Steep spectrum radio Sources associated with active galactic nuclei (AGN) may contain remnants of past AGN activity episodes. Novel instruments like the LOw Frequency ARray (LOFAR) are enabling studies of these fascinating structures to be made at tens to hundreds of MHz with sufficient resolution to analyse their complex morphology. Our goal is to characterize the integrated and resolved spectral properties of VLSS J1431+1331 and estimate Source ages based on synchrotron radio emission models, thus putting constraints on the AGN duty cycle. Using a broad spectral coverage, we have derived spectral and curvature maps, and used synchrotron ageing models to determine the time elapsed from the last time the Source plasma was energized. We used LOFAR, Giant Metrewave Radio Telescope (GMRT) and Jansky Very Large Array (VLA) data. Based on our ageing analysis, we infer that the AGN that created this Source currently has very low levels of activity or that it is switched off. The derived ages for the larger Source Component range from around 60 to 130 Myr, hinting that the AGN activity decreased or stopped around 60 Myr ago. Our analysis suggests that VLSS J1431.8+1331 is an intriguing, two-Component Source. The larger Component seems to host a faint radio core, suggesting that the Source may be an AGN radio relic. The spectral index we observe from the smaller Component is distinctly flatter at lower frequencies than the spectral index of the larger Component, suggesting the possibility that the smaller Component may be a shocked plasma bubble. From the integrated Source spectrum, we deduce that its shape and slope can be used as tracers of the activity history of this type of steep spectrum radio Source.
R Morganti - One of the best experts on this subject based on the ideXlab platform.
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The LOFAR view of intergalactic magnetic fields with giant radio galaxies
'EDP Sciences', 2020Co-Authors: C. Stuardi, R Morganti, S. P. O’sullivan, A. Bonafede, M. Brüggen, P. Dabhade, C. Horellou, E. Carretti, G. Heald, M. IacobelliAbstract:Context. Giant radio galaxies (GRGs) are physically large radio Sources that extend well beyond their host galaxy environment. Their polarization properties are affected by the poorly constrained magnetic field that permeates the intergalactic medium on megaparsec scales. A low frequency (< 200 MHz) polarization study of this class of radio Sources is now possible with LOFAR. Aims. Here we investigate the polarization properties and Faraday rotation measure (RM) of a catalog of GRGs detected in the LOFAR Two-meter Sky Survey. This is the first low frequency polarization study of a large sample of radio galaxies that were selected on their physical size. We explore the magneto-ionic properties of their under-dense environment and probe intergalactic magnetic fields using the Faraday rotation properties of their radio lobes. LOFAR is a key instrument for this kind of analysis because it can probe small amounts of Faraday dispersion (< 1 rad m−2), which are associated with weak magnetic fields and low thermal gas densities. Methods. We used RM synthesis in the 120−168 MHz band to search for polarized emission and to derive the RM and fractional polarization of each detected Source Component. We study the depolarization between 1.4 GHz and 144 MHz using images from the NRAO VLA Sky Survey. We investigate the correlation of the detection rate, the RM difference between the lobes, and the depolarization with different parameters as follows: the angular and linear size of the Sources and the projected distance from the closest foreground galaxy cluster. In our sample, we also included 3C 23
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agn duty cycle estimates for the ultra steep spectrum radio relic vlss j1431 8 1331
Astronomy and Astrophysics, 2015Co-Authors: A Shulevski, R Morganti, Peter Barthel, J J Harwood, G Brunetti, R J Van Weeren, Huub Rottgering, G J WhiteAbstract:Context. Steep spectrum radio Sources associated with active galactic nuclei (AGN) may contain remnants of past AGN activity episodes. Studying these Sources gives us insight into the AGN activity history. Novel instruments like the LOw Frequency ARray (LOFAR) are enabling studies of these fascinating structures to be made at tens to hundreds of MHz with sufficient resolution to analyse their complex morphology. Aims. Our goal is to characterize the integrated and resolved spectral properties of VESS J1431+1331 and estimate Source ages based on synchrotron radio emission models, thus putting constraints on the AGN duty cycle. Methods. Using a broad spectral coverage, we have derived spectral and curvature maps, and used synchrotron ageing models to determine the time elapsed from the last time the Source plasma was energized. We used LOFAR, Giant Metrewave Radio Telescope (GMRT) and Jansky Very Large Array (VLA) data. Results. We confirm the morphology and the spectral index values found in previous studies of this object. Based on our ageing analysis, we infer that the AGN that created this Source currently has very low levels of activity or that it is switched off. The derived ages for the larger Source Component range from around 60 to 130 Myr, hinting that the AGN activity decreased or stopped around 60 Myr ago. We observe that the area around the faint radio core located in the larger Source Component is the youngest, while the overall age of the smaller Source Component shows it to be the oldest part of the Source. Conclusions. Our analysis suggests that VLSS J1431.8+1331 is an intriguing, two-Component Source. The larger Component seems to host a faint radio core, suggesting that the Source may be an AGN radio relic. The spectral index we observe from the smaller Component is distinctly flatter at lower frequencies than the spectral index of the larger Component, suggesting the possibility that the smaller Component may be a shocked plasma bubble. From. the integrated Source spectrum, we deduce that its shape and slope can be used as tracers of the activity history of this type of steep spectrum radio Source. We discuss the implications this conclusion has for future studies of radio Sources having similar characteristics.
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agn duty cycle estimates for the ultra steep spectrum radio relic vlss j1431 8 1331
arXiv: Astrophysics of Galaxies, 2015Co-Authors: A Shulevski, R Morganti, Peter Barthel, J J Harwood, G Brunetti, R J Van Weeren, Huub Rottgering, G J WhiteAbstract:Steep spectrum radio Sources associated with active galactic nuclei (AGN) may contain remnants of past AGN activity episodes. Novel instruments like the LOw Frequency ARray (LOFAR) are enabling studies of these fascinating structures to be made at tens to hundreds of MHz with sufficient resolution to analyse their complex morphology. Our goal is to characterize the integrated and resolved spectral properties of VLSS J1431+1331 and estimate Source ages based on synchrotron radio emission models, thus putting constraints on the AGN duty cycle. Using a broad spectral coverage, we have derived spectral and curvature maps, and used synchrotron ageing models to determine the time elapsed from the last time the Source plasma was energized. We used LOFAR, Giant Metrewave Radio Telescope (GMRT) and Jansky Very Large Array (VLA) data. Based on our ageing analysis, we infer that the AGN that created this Source currently has very low levels of activity or that it is switched off. The derived ages for the larger Source Component range from around 60 to 130 Myr, hinting that the AGN activity decreased or stopped around 60 Myr ago. Our analysis suggests that VLSS J1431.8+1331 is an intriguing, two-Component Source. The larger Component seems to host a faint radio core, suggesting that the Source may be an AGN radio relic. The spectral index we observe from the smaller Component is distinctly flatter at lower frequencies than the spectral index of the larger Component, suggesting the possibility that the smaller Component may be a shocked plasma bubble. From the integrated Source spectrum, we deduce that its shape and slope can be used as tracers of the activity history of this type of steep spectrum radio Source.
A Shulevski - One of the best experts on this subject based on the ideXlab platform.
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agn duty cycle estimates for the ultra steep spectrum radio relic vlss j1431 8 1331
Astronomy and Astrophysics, 2015Co-Authors: A Shulevski, R Morganti, Peter Barthel, J J Harwood, G Brunetti, R J Van Weeren, Huub Rottgering, G J WhiteAbstract:Context. Steep spectrum radio Sources associated with active galactic nuclei (AGN) may contain remnants of past AGN activity episodes. Studying these Sources gives us insight into the AGN activity history. Novel instruments like the LOw Frequency ARray (LOFAR) are enabling studies of these fascinating structures to be made at tens to hundreds of MHz with sufficient resolution to analyse their complex morphology. Aims. Our goal is to characterize the integrated and resolved spectral properties of VESS J1431+1331 and estimate Source ages based on synchrotron radio emission models, thus putting constraints on the AGN duty cycle. Methods. Using a broad spectral coverage, we have derived spectral and curvature maps, and used synchrotron ageing models to determine the time elapsed from the last time the Source plasma was energized. We used LOFAR, Giant Metrewave Radio Telescope (GMRT) and Jansky Very Large Array (VLA) data. Results. We confirm the morphology and the spectral index values found in previous studies of this object. Based on our ageing analysis, we infer that the AGN that created this Source currently has very low levels of activity or that it is switched off. The derived ages for the larger Source Component range from around 60 to 130 Myr, hinting that the AGN activity decreased or stopped around 60 Myr ago. We observe that the area around the faint radio core located in the larger Source Component is the youngest, while the overall age of the smaller Source Component shows it to be the oldest part of the Source. Conclusions. Our analysis suggests that VLSS J1431.8+1331 is an intriguing, two-Component Source. The larger Component seems to host a faint radio core, suggesting that the Source may be an AGN radio relic. The spectral index we observe from the smaller Component is distinctly flatter at lower frequencies than the spectral index of the larger Component, suggesting the possibility that the smaller Component may be a shocked plasma bubble. From. the integrated Source spectrum, we deduce that its shape and slope can be used as tracers of the activity history of this type of steep spectrum radio Source. We discuss the implications this conclusion has for future studies of radio Sources having similar characteristics.
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agn duty cycle estimates for the ultra steep spectrum radio relic vlss j1431 8 1331
arXiv: Astrophysics of Galaxies, 2015Co-Authors: A Shulevski, R Morganti, Peter Barthel, J J Harwood, G Brunetti, R J Van Weeren, Huub Rottgering, G J WhiteAbstract:Steep spectrum radio Sources associated with active galactic nuclei (AGN) may contain remnants of past AGN activity episodes. Novel instruments like the LOw Frequency ARray (LOFAR) are enabling studies of these fascinating structures to be made at tens to hundreds of MHz with sufficient resolution to analyse their complex morphology. Our goal is to characterize the integrated and resolved spectral properties of VLSS J1431+1331 and estimate Source ages based on synchrotron radio emission models, thus putting constraints on the AGN duty cycle. Using a broad spectral coverage, we have derived spectral and curvature maps, and used synchrotron ageing models to determine the time elapsed from the last time the Source plasma was energized. We used LOFAR, Giant Metrewave Radio Telescope (GMRT) and Jansky Very Large Array (VLA) data. Based on our ageing analysis, we infer that the AGN that created this Source currently has very low levels of activity or that it is switched off. The derived ages for the larger Source Component range from around 60 to 130 Myr, hinting that the AGN activity decreased or stopped around 60 Myr ago. Our analysis suggests that VLSS J1431.8+1331 is an intriguing, two-Component Source. The larger Component seems to host a faint radio core, suggesting that the Source may be an AGN radio relic. The spectral index we observe from the smaller Component is distinctly flatter at lower frequencies than the spectral index of the larger Component, suggesting the possibility that the smaller Component may be a shocked plasma bubble. From the integrated Source spectrum, we deduce that its shape and slope can be used as tracers of the activity history of this type of steep spectrum radio Source.
Daniel Sauter - One of the best experts on this subject based on the ideXlab platform.
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2005), Heterogeneity in southern Central Indian Ridge MORB: Implications for ridge‐hot spot interaction, Geochem. Geophys
2016Co-Authors: Bramley J Murton, A G Tindle, Andrew J Milton, Daniel SauterAbstract:[1] Between the Rodrigues Triple Junction and the Marie Celeste fracture zone, basalts from the Central Indian Ridge (CIR) exhibit an enrichment in incompatible elements that increases in intensity northward. In addition, H2O/TiO2, Al[8], and Dy/Yb ratios increase, while Na[8] remains unchanged and Fe[8] decreases. Evolution of the enriched magma appears to be affected by elevated water contents, which lower the mantle solidus, thereby increasing the initial depth of melting, as well as delaying plagioclase crystallization. However, the enrichment affecting the northern samples is not a just function of hydrous mantle melting and crystallization. Instead of trending toward a small melt fraction from the mantle, as predicted by hydrous melting models, the CIR samples lie on a mixing line between N-MORB and a Source Component that closely resembles present-day Réunion hot spot lavas. Thus it appears that while hydrous melting and crystallization affect the CIR, the enriched and wet mantle originates from the Réunion hot spot, where it migrates eastward toward the CIR, against the direction of motion of the lithosphere
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heterogeneity in southern central indian ridge morb implications for ridge hot spot interaction
Geochemistry Geophysics Geosystems, 2005Co-Authors: Bramley J Murton, A G Tindle, Andrew J Milton, Daniel SauterAbstract:Between the Rodrigues Triple Junction and the Marie Celeste fracture zone, basalts from the Central Indian Ridge (CIR) exhibit an enrichment in incompatible elements that increases in intensity northward. In addition, H2O/TiO2, Al[8], and Dy/Yb ratios increase, while Na[8] remains unchanged and Fe[8] decreases. Evolution of the enriched magma appears to be affected by elevated water contents, which lower the mantle solidus, thereby increasing the initial depth of melting, as well as delaying plagioclase crystallization. However, the enrichment affecting the northern samples is not a just function of hydrous mantle melting and crystallization. Instead of trending toward a small melt fraction from the mantle, as predicted by hydrous melting models, the CIR samples lie on a mixing line between N-MORB and a Source Component that closely resembles present-day Reunion hot spot lavas. Thus it appears that while hydrous melting and crystallization affect the CIR, the enriched and wet mantle originates from the Reunion hot spot, where it migrates eastward toward the CIR, against the direction of motion of the lithosphere.
Huub Rottgering - One of the best experts on this subject based on the ideXlab platform.
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agn duty cycle estimates for the ultra steep spectrum radio relic vlss j1431 8 1331
Astronomy and Astrophysics, 2015Co-Authors: A Shulevski, R Morganti, Peter Barthel, J J Harwood, G Brunetti, R J Van Weeren, Huub Rottgering, G J WhiteAbstract:Context. Steep spectrum radio Sources associated with active galactic nuclei (AGN) may contain remnants of past AGN activity episodes. Studying these Sources gives us insight into the AGN activity history. Novel instruments like the LOw Frequency ARray (LOFAR) are enabling studies of these fascinating structures to be made at tens to hundreds of MHz with sufficient resolution to analyse their complex morphology. Aims. Our goal is to characterize the integrated and resolved spectral properties of VESS J1431+1331 and estimate Source ages based on synchrotron radio emission models, thus putting constraints on the AGN duty cycle. Methods. Using a broad spectral coverage, we have derived spectral and curvature maps, and used synchrotron ageing models to determine the time elapsed from the last time the Source plasma was energized. We used LOFAR, Giant Metrewave Radio Telescope (GMRT) and Jansky Very Large Array (VLA) data. Results. We confirm the morphology and the spectral index values found in previous studies of this object. Based on our ageing analysis, we infer that the AGN that created this Source currently has very low levels of activity or that it is switched off. The derived ages for the larger Source Component range from around 60 to 130 Myr, hinting that the AGN activity decreased or stopped around 60 Myr ago. We observe that the area around the faint radio core located in the larger Source Component is the youngest, while the overall age of the smaller Source Component shows it to be the oldest part of the Source. Conclusions. Our analysis suggests that VLSS J1431.8+1331 is an intriguing, two-Component Source. The larger Component seems to host a faint radio core, suggesting that the Source may be an AGN radio relic. The spectral index we observe from the smaller Component is distinctly flatter at lower frequencies than the spectral index of the larger Component, suggesting the possibility that the smaller Component may be a shocked plasma bubble. From. the integrated Source spectrum, we deduce that its shape and slope can be used as tracers of the activity history of this type of steep spectrum radio Source. We discuss the implications this conclusion has for future studies of radio Sources having similar characteristics.
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agn duty cycle estimates for the ultra steep spectrum radio relic vlss j1431 8 1331
arXiv: Astrophysics of Galaxies, 2015Co-Authors: A Shulevski, R Morganti, Peter Barthel, J J Harwood, G Brunetti, R J Van Weeren, Huub Rottgering, G J WhiteAbstract:Steep spectrum radio Sources associated with active galactic nuclei (AGN) may contain remnants of past AGN activity episodes. Novel instruments like the LOw Frequency ARray (LOFAR) are enabling studies of these fascinating structures to be made at tens to hundreds of MHz with sufficient resolution to analyse their complex morphology. Our goal is to characterize the integrated and resolved spectral properties of VLSS J1431+1331 and estimate Source ages based on synchrotron radio emission models, thus putting constraints on the AGN duty cycle. Using a broad spectral coverage, we have derived spectral and curvature maps, and used synchrotron ageing models to determine the time elapsed from the last time the Source plasma was energized. We used LOFAR, Giant Metrewave Radio Telescope (GMRT) and Jansky Very Large Array (VLA) data. Based on our ageing analysis, we infer that the AGN that created this Source currently has very low levels of activity or that it is switched off. The derived ages for the larger Source Component range from around 60 to 130 Myr, hinting that the AGN activity decreased or stopped around 60 Myr ago. Our analysis suggests that VLSS J1431.8+1331 is an intriguing, two-Component Source. The larger Component seems to host a faint radio core, suggesting that the Source may be an AGN radio relic. The spectral index we observe from the smaller Component is distinctly flatter at lower frequencies than the spectral index of the larger Component, suggesting the possibility that the smaller Component may be a shocked plasma bubble. From the integrated Source spectrum, we deduce that its shape and slope can be used as tracers of the activity history of this type of steep spectrum radio Source.
