An X‐Ray Study of Magnetic Field Strengths and Particle Content in the Lobes of FR II Radio Sources

Croston, J. H.; Hardcastle, M. J.; Harris, D. E.; Belsole, E.; Birkinshaw, Mark; Worrall, D. M.

doi:10.1086/430170

Cited by 317 publications

(506 citation statements)

References 50 publications

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“…We note in this context that the above equipartition magnetic field strength is compatible with the typical values 0.3 nT < B < 3 nT found by means of multiwavelength analysis of the non-thermal lobes' emission (e.g. Kataoka & Stawarz 2005;Croston et al 2005). However, the ambient gas density within the old cocoon of DDRGs is likely lower than that of the typical FRII-type sources with linear sizes comparable to those characteristic for the inner double structures.…”

Section: Independent Solution For the Inner Lobessupporting

confidence: 85%

Spectral ageing analysis and dynamical analysis of the double-double radio galaxy J1548–3216

Machalski¹,

Jamrozy²,

Konar³

2010

A&A

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Context. Determining ages of the outer and the inner lobes of so-called double-double radio galaxies (DDRGs) is crucial for understanding the active cycles of galactic nuclei, the phases of interruption of the jet flow, and physical conditions in the surrounding galactic and intergalactic medium governing the jets' propagation. A recognition and understanding of these conditions during the restarted jet activity is of special interest. Aims. We determine the ages and other physical characteristics of the outer and the inner lobes of the DDRG J1548−3216, as well as the properties of the surrounding environment during the original and the restarted phase of the jets' activity. Methods. Using the new low-frequency and high-frequency radio images of this galaxy, we determined the shape of the spectrum along its lobes and performed the classical spectral-ageing analysis. On the other hand, we applied the analytical model of the jet's dynamics, which allowed us to derive the physical conditions for the source's evolution during the original jet propagation through the unperturbed IGM, as well as those when the restarted new jet propagates inside the outer cocoon formed by the old jet material that passed through the jet terminal shock. Results. The dynamical age estimate of the outer and the inner lobes is 132 ± 28 Myr and ∼9 ± 4 Myr, respectively. The synchrotron age in the outer lobes systematically rises from ∼25 Myr in the vicinity of the lobes' edges to about 65-75 Myr in the centre of the old cocoon. These ages imply an average expansion speed along the jets' axis: (0.012 ± 0.003)c in the outer lobes and (0.058 ± 0.025)c in the inner lobes, but the latter speed would be ∼0.25 c when they were of age less than 1 Myr. We find that the jet power during the restarted activity is about ten-fold fainter than that of the original jet. Similar disproportion is found for the internal pressures and the magnetic field strengths in the old cocoon and those in the inner lobes. This disproportion can be effectively reduced by assuming the same equations of state for the emitting particles and the magnetic fields within the old and the new lobes. However, we think that our assumption of the non-relativistic equation of state for the old cocoon and the relativistic one for the new lobes is more justified.

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Section: Independent Solution For the Inner Lobessupporting

confidence: 85%

Spectral ageing analysis and dynamical analysis of the double-double radio galaxy J1548–3216

Machalski¹,

Jamrozy²,

Konar³

2010

A&A

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“…Equipartition is actually supported by observations of classical double FR II radio-galaxies in the radio and X-ray bands, and appears as an educated guess (Wilson et al 2000;Croston et al 2004Croston et al , 2005Belsole et al 2004). …”

Section: Constraints On the Physical Parameters Of The Hot Spot And Lobementioning

confidence: 70%

CMB quenching of high-redshift radio-loud AGNs

Ghisellini

Haardt

Ciardi

et al. 2015

Mon. Not. R. Astron. Soc.

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The very existence of more than a dozen of high-redshift (z ∼ > 4) blazars indicates that a much larger population of misaligned powerful jetted AGN was already in place when the Universe was ∼ < 1.5 Gyr old. Such parent population proved to be very elusive, and escaped direct detection in radio surveys so far. High redshift blazars themselves seem to be failing in producing extended radio-lobes, raising questions about the connection between such class and the vaster population of radio-galaxies. We show that the interaction of the jet electrons with the intense cosmic microwave background (CMB) radiation explains the lack of extended radio emission in high redshift blazars and in their parent population, helping to explain the apparently missing misaligned counterparts of high redshift blazars. On the other hand, the emission from the more compact and more magnetised hot spots are less affected by the enhanced CMB energy density. By modelling the spectral energy distribution of blazar lobes and hot spots we find that most of them should be detectable by low frequency deep radio observations, e.g., by LOw-Frequency ARray for radio astronomy (LOFAR) and by relatively deep X-ray observations with good angular resolution, e.g., by the Chandra satellite. At high redshifts, the emission of a misaligned relativistic jet, being de-beamed, is missed by current large sky area surveys. The isotropic flux produced in the hot spots can be below ∼ 1 mJy and the isotropic lobe radio emission is quenched by the CMB cooling. Consequently, even sources with very powerful jets can go undetected in current radio surveys, and misclassified as radio-quiet AGNs.

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“…Unfortunately, despite our understanding of FRII radio galaxies (e.g. Croston et al 2005, magnetic fields in low-power radio galaxies are still not well constrained observationally. We therefore need to rely on the equipartition condition to derive the normalization of the magnetic energy density B 0 .…”

Section: Initial Magnetic Energy Density Bmentioning

confidence: 99%

Search and modelling of remnant radio galaxies in the LOFAR Lockman Hole field

Brienza

Godfrey

Morganti

et al. 2017

A&A

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178

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Context. The phase of radio galaxy evolution after the jets have switched off, often referred to as the remnant phase, is poorly understood and very few sources in this phase are known. Aims. In this work we present an extensive search for remnant radio galaxies in the Lockman Hole, a well-studied extragalactic field. We create mock catalogues of low-power radio galaxies based on Monte Carlo simulations to derive first-order predictions of the fraction of remnants in radio flux limited samples for comparison with our Lockman-Hole sample. Methods. Our search for remnant radio galaxies is based on LOFAR observations at 150 MHz combined with public survey data at higher frequencies. To enhance the selection process, and obtain a more complete picture of the remnant population, we use spectral criteria such as ultra-steep spectral index and high spectral curvature, and morphological criteria such as low radio core prominence and relaxed shapes to identify candidate remnant radio galaxies. Mock catalogues of radio galaxies are created based on existing spectral and dynamical evolution models combined with observed source properties. Results. We have identified 23 candidate remnant radio galaxies which cover a variety of morphologies and spectral characteristics. We suggest that these different properties are related to different stages of the remnant evolution. We find that ultra-steep spectrum remnants represent only a fraction of our remnant sample suggesting a very rapid luminosity evolution of the radio plasma. Results from mock catalogues demonstrate the importance of dynamical evolution in the remnant phase of low-power radio galaxies to obtain fractions of remnant sources consistent with our observations. Moreover, these results confirm that ultra-steep spectrum remnants represent only a small subset of the entire population (∼50%) when frequencies higher than 1400 MHz are not included in the selection process, and that they are biased towards old ages.

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An X‐Ray Study of Magnetic Field Strengths and Particle Content in the Lobes of FR II Radio Sources

Cited by 317 publications

References 50 publications

Spectral ageing analysis and dynamical analysis of the double-double radio galaxy J1548–3216

Spectral ageing analysis and dynamical analysis of the double-double radio galaxy J1548–3216

CMB quenching of high-redshift radio-loud AGNs

Search and modelling of remnant radio galaxies in the LOFAR Lockman Hole field

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