scholarly journals Models of particle acceleration in galaxy clusters by MHD turbulence

2009 ◽  
Vol 5 (H15) ◽  
pp. 466-467
Author(s):  
G. Brunetti
Keyword(s):  
Particle Acceleration ◽  
Radio Emission ◽  
Galaxy Clusters ◽  
Indirect Evidence ◽  
Mhd Turbulence ◽  
Radio Data ◽  
Central Cluster ◽  
Relativistic Particles

AbstractPresent radio data provide indirect evidence that diffuse radio emission in the central cluster regions may originate from turbulent-acceleration of relativistic particles. I was invited to discuss models of particle acceleration by MHD turbulence in clusters and in these pages I briefly touch the main points of my talk.

Particle acceleration in galaxy clusters via MHD turbulence

2006 ◽  
Vol 327 (5-6) ◽  
pp. 615-618 ◽  
Author(s):  
G. Brunetti
Keyword(s):  
Particle Acceleration ◽  
Galaxy Clusters ◽  
Mhd Turbulence

scholarly journals High energy emission from galaxy clusters and particle acceleration due to MHD turbulence

2009 ◽  
Author(s):  
G. Brunetti ◽  
P. Blasi ◽  
R. Cassano ◽  
S. Gabici ◽  
Denis Bastieri ◽  
...  
Keyword(s):  
Particle Acceleration ◽  
Galaxy Clusters ◽  
High Energy ◽  
Mhd Turbulence ◽  
Energy Emission ◽  
High Energy Emission

scholarly journals A LOFAR study of non-merging massive galaxy clusters

2019 ◽  
Vol 622 ◽  
pp. A24 ◽  
Author(s):  
F. Savini ◽  
A. Bonafede ◽  
M. Brüggen ◽  
D. Rafferty ◽  
T. Shimwell ◽  
...  
Keyword(s):  
Particle Acceleration ◽  
Radio Emission ◽  
Galaxy Clusters ◽  
Large Scale ◽  
Low Frequency ◽  
Cosmic Ray ◽  
Dynamical State ◽  
Core Cluster ◽  
Spectrum Radio ◽  
Massive Clusters

Centrally located diffuse radio emission has been observed in both merging and non-merging galaxy clusters. Depending on their morphology and size, we distinguish between giant radio haloes, which occur predominantly in merging clusters, and mini haloes, which are found in non-merging, cool-core clusters. In recent years, cluster-scale radio emission has also been observed in clusters with no sign of major mergers, showing that our knowledge of the mechanisms that lead to particle acceleration in the intra-cluster medium (ICM) is still incomplete. Low-frequency sensitive observations are required to assess whether the emission discovered in these few cases is common in galaxy clusters or not. With this aim, we carried out a campaign of observations with the LOw Frequency ARay (LOFAR) in the frequency range 120–168 MHz of nine massive clusters selected from the Planck SZ catalogue, which had no sign of major mergers. In this paper, we discuss the results of the observations that have led to the largest cluster sample studied within the LOFAR Two-metre Sky Survey, and we present Chandra X-ray data used to investigate the dynamical state of the clusters, verifying that the clusters are currently not undergoing major mergers, and to search for traces of minor or off-axis mergers. We discover large-scale steep-spectrum emission around mini haloes in the cool-core clusters PSZ1G139.61+24 and RXJ1720.1+2638, which is not observed around the mini halo in the non-cool-core cluster A1413. We also discover a new 570 kpc-halo in the non-cool-core cluster RXCJ0142.0+2131. We derived new upper limits to the radio power for clusters in which no diffuse radio emission was found, and we discuss the implication of our results to constrain the cosmic-ray energy budget in the ICM. We conclude that radio emission in non-merging massive clusters is not common at the sensitivity level reached by our observations and that no clear connection with the cluster dynamical state is observed. Our results might indicate that the sloshing of a dense cool core could trigger particle acceleration on larger scales and generate steep-spectrum radio emission.

scholarly journals Characterizing the radio emission from the binary galaxy cluster merger Abell 2146

2019 ◽  
Vol 622 ◽  
pp. A21 ◽  
Author(s):  
D. N. Hoang ◽  
T. W. Shimwell ◽  
R. J. van Weeren ◽  
H. J. A. Röttgering ◽  
A. Botteon ◽  
...  
Keyword(s):  
Particle Acceleration ◽  
Radio Emission ◽  
Low Frequency ◽  
Galaxy Cluster ◽  
Relativistic Electrons ◽  
Extended Source ◽  
Very Large Array ◽  
Radio Halo ◽  
Extended Radio ◽  
Relativistic Particles

Context. Collisions of galaxy clusters generate shocks and turbulence in the intra-cluster medium (ICM). The presence of relativistic particles and magnetic fields is inferred through the detection of extended synchrotron radio sources such as haloes and relics and implies that merger shocks and turbulence are capable of (re-)accelerating particles to relativistic energies. However, the precise relationship between merger shocks, turbulence, and extended radio emission is still unclear. Studies of the most simple binary cluster mergers are important to help understand the particle acceleration in the ICM. Aims. Our main aim is to study the properties of the extended radio emission and particle acceleration mechanism(s) associated with the generation of relativistic particles in the ICM. Methods. We measure the low-frequency radio emission from the merging galaxy cluster Abell 2146 with LOFAR at 144 MHz. We characterize the spectral properties of the radio emission by combining these data with data from archival Giant Metrewave Radio Telescope (GMRT) at 238 MHz and 612 MHz and Very Large Array (VLA) at 1.5 GHz. Results. We observe extended radio emission at 144 MHz behind the NW and SE shocks. Across the NW extended source, the spectral index steepens from −1.06 ± 0.06 to −1.29 ± 0.09 in the direction of the cluster centre. This spectral behaviour suggests that a relic is associated with the NW upstream shock. The precise nature of the SE extended emission is unclear. It may be a radio halo bounded by a shock or a superposition of a relic and halo. At 144 MHz, we detect a faint emission that was not seen with high-frequency observations, implying a steep (α <  −1.3) spectrum nature of the bridge emission. Conclusions. Our results imply that the extended radio emission in Abell 2146 is probably associated with shocks and turbulence during cluster merger. The relativistic electrons in the NW and SE may originate from fossil plasma and thermal electrons, respectively.

Particle Acceleration and Diffusion in Fossil Radio Plasma

2002 ◽  
Vol 12 ◽  
pp. 528-530
Author(s):  
Torsten A. Enβlin
Keyword(s):  
Particle Acceleration ◽  
Radio Emission ◽  
Magnetic Confinement ◽  
Radio Galaxies ◽  
Clusters Of Galaxies ◽  
Strong Activity ◽  
And Shock Waves ◽  
And Diffusion ◽  
Ubiquitous Presence ◽  
Relativistic Particles

AbstractThe strong activity of radio galaxies should have led to a nearly ubiquitous presence of fossil radio plasma in the denser regions of the inter-galactic medium as clusters, groups and filaments of galaxies. This fossil radio plasma can contain large quantities of relativistic particles (electrons and possibly protons) by magnetic confinement. These particles might be released and/or re-energized under environmental influences as turbulence and shock waves. Possible connections of such processes to the formation of the observed sources of diffuse radio emission in clusters of galaxies (the cluster radio halos and the cluster radio relics) are discussed.

scholarly journals Regulation of Thermal Conductivity in Hot Galaxy Clusters by MHD Turbulence

2008 ◽  
Vol 681 (2) ◽  
pp. L65-L68 ◽  
Author(s):  
Steven A. Balbus ◽  
Christopher S. Reynolds
Keyword(s):  
Thermal Conductivity ◽  
Galaxy Clusters ◽  
Mhd Turbulence

Transition Radio Emission of Mildly Relativistic Particles

1994 ◽  
pp. 243-244
Author(s):  
G. D. Fleishman ◽  
K. Yu. Platonov
Keyword(s):  
Radio Emission ◽  
Relativistic Particles

scholarly journals The relation between the diffuse X-ray luminosity and the radio power of the central AGN in galaxy groups

2020 ◽  
Vol 497 (2) ◽  
pp. 2163-2174
Author(s):  
T Pasini ◽  
M Brüggen ◽  
F de Gasperin ◽  
L Bîrzan ◽  
E O’Sullivan ◽  
...  
Keyword(s):  
Radio Emission ◽  
Galaxy Clusters ◽  
Active Galactic Nucleus ◽  
Statistical Tests ◽  
Control Sample ◽  
Radio Galaxies ◽  
Very Large Array ◽  
X Ray ◽  
Galaxy Groups ◽  
Hydrodynamical Simulations

ABSTRACT Our understanding of how active galactic nucleus feedback operates in galaxy clusters has improved in recent years owing to large efforts in multiwavelength observations and hydrodynamical simulations. However, it is much less clear how feedback operates in galaxy groups, which have shallower gravitational potentials. In this work, using very deep Very Large Array and new MeerKAT observations from the MIGHTEE survey, we compiled a sample of 247 X-ray selected galaxy groups detected in the COSMOS field. We have studied the relation between the X-ray emission of the intra-group medium and the 1.4 GHz radio emission of the central radio galaxy. For comparison, we have also built a control sample of 142 galaxy clusters using ROSAT and NVSS data. We find that clusters and groups follow the same correlation between X-ray and radio emission. Large radio galaxies hosted in the centres of groups and merging clusters increase the scatter of the distribution. Using statistical tests and Monte Carlo simulations, we show that the correlation is not dominated by biases or selection effects. We also find that galaxy groups are more likely than clusters to host large radio galaxies, perhaps owing to the lower ambient gas density or a more efficient accretion mode. In these groups, radiative cooling of the intra-cluster medium could be less suppressed by active galactic nucleus heating. We conclude that the feedback processes that operate in galaxy clusters are also effective in groups.

scholarly journals Jupiter's Radiation Belts and Upper Atmosphere

1974 ◽  
Vol 65 ◽  
pp. 375-383
Author(s):  
Joseph J. Degioanni ◽  
John R. Dickel
Keyword(s):  
Radio Emission ◽  
Radiation Belts ◽  
Upper Atmosphere ◽  
Mixing Ratio ◽  
Frequency Range ◽  
Emission Data ◽  
High Energies ◽  
Isotropic Distribution ◽  
Relativistic Particles ◽  
Flat Distribution

Models of Jupiter's radiation belts have been constructed to determine the distribution of particles and their energies which will produce the observed decimetric radio emission. Data on the spectrum and the variation of emission with Jovian longitude have been used to show that the relativistic particles have a nearly isotropic distribution with high energies (of order 100 MeV) within 2 Jovian radii and a very flat distribution in the equatorial plane of low energy particles further out in the magnetosphere.Subtraction of the emission predicted by this model from the total radio emission shows that the thermal contribution in the frequency range between 3000 and 10000 MHz is somewhat less than had been previously expected. (The brightness temperature of the planetary disk is 180 K at 3000 MHz, for example.) This suggests that the ammonia mixing ratio in Jupiter's upper atmosphere may be as high as 0.002.

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