Non-Thermal Emission from Extragalactic Radio Sources: A High Resolution - Broad Band Approach

Brunetti, G.

doi:10.1007/1-4020-2406-1_3

Cited by 5 publications

(3 citation statements)

References 111 publications

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“…(11) it is clear that such a problem does not arise for E x B-drifting beams. See also Brunetti (2002), Hardcastle et al (2003), andStawarz (2004) for similar well-studied sources.…”

Section: Realistic Jetsmentioning

confidence: 89%

“…Blandford (2001), and Beresnyak et al (2003), with a few notable exceptions, e.g. Reipurth & Heathcote (1993), Scheuer (1996), Prieto et al (2002), Brunetti (2002), andStawarz (2003). A possible reason for this lack of widespread acceptance may have been a concern about whether or not the beams allowed a stable transport of a broad energy distribution of high-energy charges, in the form of an ordered E x B-drift.…”

Section: Introductionmentioning

confidence: 99%

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The physics of E × B-drifting jets

Kundt

Krishna

2004

J Astrophys Astron

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E x B-drifting jets have been generally ignored for the past 25 years even though they may well describe all the astrophysical jet sources, both on galactic and stellar scales. Here we present closed-form solutions for their joint field-and-particle distribution, argue that the observed jets are near equipartition, with extremely relativistic, mono-energetic e ± -pairs of bulk Lorentz factor γ < ∼ 10 4 , and are first-order stable. We describe plausible mechanisms for the jets' (i) formation, (ii) propagation, and (iii) termination. Wherever a beam meets with resistance, its frozen-in Poynting flux transforms the delta-shaped energy distribution of the pairs into an almost white power law, E 2 N E ∼ E −ǫ with ǫ > ∼ 0, via single-step falls through the huge convected potential.

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“…(11) it is clear that such a problem does not arise for E x B-drifting beams. See also Brunetti (2002), Hardcastle et al (2003), andStawarz (2004) for similar well-studied sources.…”

Section: Realistic Jetsmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

The physics of E × B-drifting jets

Kundt

Krishna

2004

J Astrophys Astron

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“…with energy between γ min ∝ (ν 1 /B eq ) 1/2 and γ max ∝ (ν 2 /B eq ) 1/2 are present in the radio source. This approach neglects the contribution of the electrons emitting below 10 MHz and, as a more serious bias, in radio sources with different B eq selects different energy bands of the electron population because the energy of the electrons which emit synchrotron radiation at a given frequency depends on the magnetic field intensity [36]. A more consistent approach is to calculate the minimum energy conditions, in which B eq does not depend on the emitted frequency band but directly on the low energy cut-off of the electron spectrum (typically assumed to be γ min = 100).…”

Section: Radio Lobe Compositionmentioning

confidence: 99%

Evidence for AGN Feedback in Galaxy Clusters and Groups

Gitti

Brighenti

McNamara

2012

Advances in Astronomy

145

151

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The current generation of flagship X-ray missions, Chandra and XMM-Newton, has changed our understanding of the so-called "cool core" galaxy clusters and groups. Instead of the initial idea that the thermal gas is cooling and flowing toward the center, the new picture envisages a complex dynamical evolution of the intra-cluster medium (ICM) regulated by the radiative cooling and the nongravitational heating from the active galactic nucleus (AGN). Understanding the physics of the hot gas and its interplay with the relativistic plasma ejected by the AGN is key for understanding the growth and evolution of galaxies and their central black holes, the history of star formation, and the formation of large-scale structures. It has thus become clear that the feedback from the central black hole must be taken into account in any model of galaxy evolution. In this paper, we draw a qualitative picture of the current knowledge of the effects of the AGN feedback on the ICM by summarizing the recent results in this field.I.

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AGN duty cycle estimates for the ultra-steep spectrum radio relic VLSS J1431.8+1331

Shulevski

Morganti

Barthel

et al. 2015

A&A

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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 VLSS 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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Non-Thermal Emission from Extragalactic Radio Sources: A High Resolution - Broad Band Approach

Cited by 5 publications

References 111 publications

The physics of E × B-drifting jets

The physics of E × B-drifting jets

Evidence for AGN Feedback in Galaxy Clusters and Groups

AGN duty cycle estimates for the ultra-steep spectrum radio relic VLSS J1431.8+1331

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