In a growing number of galaxy clusters diffuse extended radio sources have been found. These sources are not directly associated with individual cluster galaxies. The radio emission reveal the presence of cosmic rays and magnetic fields in the intracluster medium (ICM). We classify diffuse cluster radio sources into radio halos, cluster radio shocks (relics), and revived AGN fossil plasma sources. Radio halo sources can be further divided into giant halos, mini-halos, and possible “intermediate” sources. Halos are generally positioned at cluster center and their brightness approximately follows the distribution of the thermal ICM. Cluster radio shocks (relics) are polarized sources mostly found in the cluster’s periphery. They trace merger induced shock waves. Revived fossil plasma sources are characterized by their radio steep-spectra and often irregular morphologies. In this review we give an overview of the properties of diffuse cluster radio sources, with an emphasis on recent observational results. We discuss the resulting implications for the underlying physical acceleration processes that operate in the ICM, the role of relativistic fossil plasma, and the properties of ICM shocks and magnetic fields. We also compile an updated list of diffuse cluster radio sources which will be available on-line (
 http://galaxyclusters.com
 ). We end this review with a discussion on the detection of diffuse radio emission from the cosmic web.

/pdf/diffuse-radio-emission-from-galaxy-clusters-1oym8won5e.pdf

Diffuse Radio Emission from Galaxy Clusters

We present multifrequency Very Large Array (VLA) observations of two giant quasars, 0437-244 and 1025-229, from the Molonglo Complete Sample. These sources have well-defined FR II radio structure, possible one-sided jets, no significant depolarization between 1365 and 4935 MHz and low rotation measure (\ RM \ < 20 rad m(-2)). The giant sources are defined to be those with overall projected size greater than or equal to 1 Mpc. We have compiled a sample of about 50 known giant radio sources from the literature, and have compared some of their properties with a complete sample of 3CR radio sources of smaller sizes to investigate the evolution of giant sources, and test their consistency with the unified scheme for radio galaxies and quasars. We find an inverse correlation between the degree of core prominence and total radio luminosity, and show that the giant radio sources have similar core strengths to smaller sources of similar total luminosity. Hence their large sizes are unlikely to be caused by stronger nuclear activity. The degree of collinearity of the giant sources is also similar to that of the sample of smaller sources. The luminosity-size diagram shows that the giant sources are less luminous than our sample of smaller sized 3CR sources, consistent with evolutionary scenarios in which the giants have evolved from the smaller sources, losing energy as they expand to these large dimensions. For the smaller sources, radiative losses resulting from synchrotron radiation are more significant while for the giant sources the equipartition magnetic fields are smaller and inverse Compton lass owing to microwave background radiation is the dominant process. The radio properties of the giant radio galaxies and quasars are consistent with the unified scheme.

Giant radio sources

Radio galaxies and feedback from AGN jets

In a growing number of galaxy clusters diffuse extended radio sources have been found. These sources are not directly associated with individual cluster galaxies. The radio emission reveal the presence of cosmic rays and magnetic fields in the intracluster medium (ICM). We classify diffuse cluster radio sources into radio halos, cluster radio shocks (relics), and revived AGN fossil plasma sources. Radio halo sources can be further divided into giant halos, mini-halos, and possible `intermediate' sources. Halos are generally positioned at cluster center and their brightness approximately follows the distribution of the thermal ICM. Cluster radio shocks (relics) are polarized sources mostly found in the cluster's periphery. They trace merger induced shock waves. Revived fossil plasma sources are characterized by their radio steep-spectra and often irregular morphologies. In this review we give an overview of the properties of diffuse cluster radio sources, with an emphasis on recent observational results. We discuss the resulting implications for the underlying physical acceleration processes that operate in the ICM, the role of relativistic fossil plasma, and the properties of ICM shocks and magnetic fields. We also compile an updated list of diffuse cluster radio sources which will be available on-line this http URL. We end this review with a discussion on the detection of diffuse radio emission from the cosmic web.

/pdf/diffuse-radio-emission-from-galaxy-clusters-2rto858mkw.pdf

The interpretation of strong double radio sources in terms of the "beam" model is reviewed. Implications of this model for source evolution and the nature of radio trails are briefly discussed. A final section is concerned with deductions about the properties of compact and variable components in quasars and galactic nuclei.

https://iopscience.iop.org/article/10.1088/0031-8949/17/3/020/pdf

Extended and compact extragalactic radio sources: interpretation and theory.

Two medels for the formation of tailed'' radio sources like 3C 129 are developed. Both models assume that the tails are the result of the rapid motion of an active galaxy through the relatively dense gas in a cluster of galaxies. The first model is a modification of current models of normal symmetrical double radio sources, with the effects of the motion of the parent galaxy and of the thermal pressure of the intracluster gas included. The second model assumes that the galaxy has a long, permanently attached, magnetospheric tail, similar to the geomagnetic tail, generated by the action of the intracluster gas flow on the intrinsic magnetic field of the galaxy. This tail is illuminated at intervals by outbursts of high energy electrons from the galaxy. An attempt is made to fit both models to 3C 129 to see if they give a good explanation of the observed characteristics of this source, and to determine the physical conditions in the intracluster gas. While both models give good fits to the shape of the tail, the magnetospheric model gives a better fit to the observed spectral indices, more » as well as relbes ia the interpretation of the polarization solving some difficulties in the interpretation of the polarization of the radio emission of 3C 129. The relation of the models to normal symmetric double radio sources, and to intermediate cases like 3C 465 is discussed. The derived values of the intracluster density and temperature are considered. (auth) « less

W. J. Jaffe

Papers

Dynamical Models of Tailed Radio Sources in Clusters of Galaxies