Anomalous radio-loudness of Cygnus A and other powerful radio galaxies

Barthel, Pieter; Arnaud, K. A.

doi:10.1093/mnras/283.2.l45

Cited by 100 publications

(104 citation statements)

References 0 publications

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“…However, 3C 388 is the only low-excitation FR II-type radio galaxy in the sample, which, as postulated by Hardcastle (2004), may imply that it is an intrinsically low jet power (i.e., more FR I-like) source, with its high 178 MHz radio luminosity due to a rich surrounding environment (cf. Barthel & Arnaud 1996). Our measurement of a relatively low X-ray core luminosity for this source is consistent with this argument.…”

Section: Components With High Intrinsic Absorptionsupporting

confidence: 86%

ChandraandXMM‐NewtonObservations of a Sample of Low‐Redshift FR I and FR II Radio Galaxy Nuclei

Evans

Worrall

Hardcastle

et al. 2006

ApJ

187

245

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We present spectral results from Chandra and XMM-Newton observations of a sample of 22 low-redshift (z < 0:1) radio galaxies and consider whether the core emission originates from the base of a relativistic jet, or an accretion flow, or contains contributions from both. We find correlations between the unabsorbed X-ray, radio, and optical fluxes and luminosities of FR I-type radio-galaxy cores, implying a common origin in the form of a jet. On the other hand, we find that the X-ray spectra of FR II-type radio galaxy cores are dominated by absorbed emission, with N H k 10 23 atoms cm À2 , which is likely to originate in an accretion flow. We discuss several models that may account for the different nuclear properties of FR I-and FR II-type cores and also demonstrate that both heavily obscured, accretion-related and unobscured, jet-related components may be present in all radio galaxy nuclei. Any absorbed, accretion-related components in FR I-type galaxies have low radiative efficiencies.

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Section: Components With High Intrinsic Absorptionsupporting

confidence: 86%

ChandraandXMM‐NewtonObservations of a Sample of Low‐Redshift FR I and FR II Radio Galaxy Nuclei

Evans

Worrall

Hardcastle

et al. 2006

ApJ

187

245

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“…Although the cluster plasma density at the location of Cygnus A is lower than in the centre of other clusters, at 15 GHz there are indications that the lobe is confined by the ICM. This is consisitent with the conclusion from Barthel & Arnaud (1996) that the slower adiabatic expansion of the radio lobes due to the larger density of the cluster environment compared to the field increases the radio luminosity.…”

Section: Comparison With Wide-angle Tailed Radio Galaxiessupporting

confidence: 85%

Multiwavelength study of Cygnus A

Steenbrugge

Blundell

Pyrzas

2014

A&A

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Context. Cygnus A, as the nearest powerful FR II radio galaxy, plays an important role in understanding jets and their impact on the surrounding intracluster medium. Aims. We explain why the nucleus is observed superposed onto the eastern lobe rather than in between the two lobes, and why the jet and counterjet are non-colinear. Methods. We made a comparative study of the radio images at different frequencies of Cygnus A, in combination with the published results on the radial velocities in the Cygnus A cluster. Results. From the morphology of the inner lobes we conclude that the lobes are not interacting with one another, but are well separated, even at low radio frequencies. We explain the location of the nucleus as the result of the proper motion of the galaxy through the cluster. The required proper motion is of the same order of magnitude as the radial velocity offset of Cygnus A with the sub-cluster it belongs to. The proper motion of the galaxy through the cluster likely also explains the non-colinearity of the jet and counterjet.

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“…For example, 3C 405 (Cygnus A) has exceptionally bright radio lobes (Barthel & Arnaud 1996) and shows a low R dr < 10, confirming the suggestion by Barthel & Arnaud, that radio luminosity is not generally a good measure of AGN power. The ISO data show that the dust emission may serve as a better isotropic indicator for the AGN strength.…”

Section: Environment and Lobe Evolutionsupporting

confidence: 71%

The ISOPHOT - MAMBO survey of 3CR radio sources: Further evidence for the unified schemes

Haas

Muller²,

Bertoldi

et al. 2004

A&A

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Abstract. We present the complete set of ISOPHOT observations of 3CR radio galaxies and quasars, which are contained in the ISO Data Archive, providing 75 mid-and far-infrared spectral energy distributions (SEDs) between 5 and 200 µm. For 28 sources they are supplemented with MAMBO 1.2 mm observations and for 15 sources with new submillimetre data from the SCUBA archive. The sample includes flat and steep spectrum quasars, broad and narrow line radio galaxies, as well as Fanaroff-Riley FR 1 and FR 2 types. The SED shapes exhibit a diversity in the infrared (IR), ranging from a smooth dominating synchrotron component in flat spectrum sources to a thermal dust bump around 60−100 µm in steep spectrum sources. The detection rate of a thermal bump in more than 50% of the cases suggests that dust emission may be a general phenomenon in these sources. We check the orientation-dependent unified scheme, in which the powerful FR 2 narrow line galaxies are quasars viewed at high inclination, so that their nuclei are hidden behind a dust torus intercepting the optical-ultraviolet AGN radiation and reemitting it in the infrared. We find that (1) both the quasars and the galaxies show a high mid-to far-infrared luminosity ratio typical for powerful AGNs and (2) -when matched in 178 MHz luminosity -both show the same ratio of isotropic farinfrared to isotropic 178 MHz lobe power. Therefore, from our large sample investigated here we find strong evidence for the orientation-dependent unification of the powerful FR 2 galaxies with the quasars. The distribution of the dust-to-lobe luminosity ratio shows a dispersion which we suggest to be most likely due to the additional influence of evolution and environment superposed on the orientation-dependent unification. We discuss our data also in the frame of the receding torus model. At the high 178 MHz luminosities of our sources above 10 26.5 W/Hz we do not find any support for this model in its original formulation and therefore we propose a refinement: The scale height of the torus might not be independent of luminosity, rather it may increase at high luminosities due to the impact of supernovae from starbursts accompanying the AGN phenomena.

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Anomalous radio-loudness of Cygnus A and other powerful radio galaxies

Cited by 100 publications

References 0 publications

ChandraandXMM‐NewtonObservations of a Sample of Low‐Redshift FR I and FR II Radio Galaxy Nuclei

ChandraandXMM‐NewtonObservations of a Sample of Low‐Redshift FR I and FR II Radio Galaxy Nuclei

Multiwavelength study of Cygnus A

The ISOPHOT - MAMBO survey of 3CR radio sources: Further evidence for the unified schemes

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