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 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.

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.

A large portion of the astrocyte proteome is dedicated to perivascular endfeet, including critical components of the electron transport chain

2021 ◽  
pp. 0271678X2110041
Author(s):  
Jesse A Stokum ◽  
Bosung Shim ◽  
Weiliang Huang ◽  
Maureen Kane ◽  
Jesse A Smith ◽  
...  
Keyword(s):  
Electron Transport ◽  
Electron Transport Chain ◽  
Glycogen Storage ◽  
Subcellular Compartment ◽  
Diffusion Limited ◽  
Transport Chain ◽  
Critical Components ◽  
And Diffusion ◽  
Ubiquitous Presence ◽  
Astrocyte Endfeet

The perivascular astrocyte endfoot is a specialized and diffusion-limited subcellular compartment that fully ensheathes the cerebral vasculature. Despite their ubiquitous presence, a detailed understanding of endfoot physiology remains elusive, in part due to a limited understanding of the proteins that distinguish the endfoot from the greater astrocyte body. Here, we developed a technique to isolate astrocyte endfeet from brain tissue, which was used to study the endfoot proteome in comparison to the astrocyte somata. In our approach, brain microvessels, which retain their endfoot processes, were isolated from mouse brain and dissociated, whereupon endfeet were recovered using an antibody-based column astrocyte isolation kit. Our findings expand the known set of proteins enriched at the endfoot from 10 to 516, which comprised more than 1/5th of the entire detected astrocyte proteome. Numerous critical electron transport chain proteins were expressed only at the endfeet, while enzymes involved in glycogen storage were distributed to the somata, indicating subcellular metabolic compartmentalization. The endfoot proteome also included numerous proteins that, while known to have important contributions to blood-brain barrier function, were not previously known to localize to the endfoot. Our findings highlight the importance of the endfoot and suggest new routes of investigation into endfoot function.

scholarly journals GAMMA RAYS FROM CLUSTERS OF GALAXIES

2007 ◽  
Vol 22 (04) ◽  
pp. 681-706 ◽  
Author(s):  
PASQUALE BLASI ◽  
STEFANO GABICI ◽  
GIANFRANCO BRUNETTI
Keyword(s):  
Gamma Rays ◽  
Large Scale ◽  
Charged Particles ◽  
Magnetic Confinement ◽  
Clusters Of Galaxies ◽  
Cherenkov Telescopes ◽  
Large Scale Structures ◽  
The Status ◽  
Physical Information ◽  
Scale Structures

Clusters of galaxies and the large scale filaments that connect neighboring clusters are expected to be sites of acceleration of charged particles and sources of non-thermal radiation from radio frequencies to gamma rays. Gamma rays are particularly interesting targets of investigation, since they may provide precious information on the nature and efficiency of the processes of acceleration and magnetic confinement of hadrons within clusters of galaxies. Here we review the status of viable scenarios that lead to the production of gamma rays from large scale structures and are compatible with the multifrequency observations that are already available. We also discuss the possibility of detection of gamma rays with space-borne telescopes such as GLAST and ground based Cherenkov telescopes, and the physical information that may be gathered from such observations.

scholarly journals A Novel Method for Estimating the Ambient Medium Density Around Distant Radio Sources from Their Observed Radio Spectra

2021 ◽  
Vol 922 (2) ◽  
pp. 197
Author(s):  
Anna Wójtowicz ◽  
Łukasz Stawarz ◽  
Jerzy Machalski ◽  
Luisa Ostorero
Keyword(s):  
Radio Emission ◽  
Ambient Medium ◽  
Radio Galaxies ◽  
Radiative Properties ◽  
Radio Continuum ◽  
Physical Parameters ◽  
Radio Sources ◽  
Data Set ◽  
Radio Structure ◽  
5 Ghz

Abstract The dynamical evolution and radiative properties of luminous radio galaxies and quasars of the FR II type, are well understood. As a result, through the use of detailed modeling of the observed radio emission of such sources, one can estimate various physical parameters of the systems, including the density of the ambient medium into which the radio structure evolves. This, however, requires rather comprehensive observational information, i.e., sampling the broadband radio continua of the targets at several frequencies, and imaging their radio structures with high resolution. Such observations are, on the other hand, not always available, especially for high-redshift objects. Here, we analyze the best-fit values of the source physical parameters, derived from extensive modeling of the largest currently available sample of FR II radio sources, for which good-quality multiwavelength radio flux measurements could be collected. In the analyzed data set, we notice a significant and nonobvious correlation between the spectral index of the nonthermal radio emission continuum, and density of the ambient medium. We derive the corresponding correlation parameters, and quantify the intrinsic scatter by means of Bayesian analysis. We propose that the discovered correlation could be used as a cosmological tool to estimate the density of ambient medium for large samples of distant radio galaxies. Our method does not require any detailed modeling of individual sources, and relies on limited observational information, namely, the slope of the radio continuum between the rest-frame frequencies 0.4 and 5 GHz, possibly combined with the total linear size of the radio structure.

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 The Ejection of QSOs from Galaxies

1989 ◽  
Vol 134 ◽  
pp. 562-564
Author(s):  
G. Burbidge ◽  
A. Hewitt
Keyword(s):  
Radio Galaxies ◽  
Active Galaxies ◽  
Powerful Radio ◽  
Galactic Centers ◽  
The 1950S ◽  
Relativistic Particles

In the 1950s, V.A. Ambartsumian (1958) proposed that galaxies result from explosive processes in galactic centers. Soon after the discovery of powerful radio galaxies in this same period, it became clear that explosive ejection of gas and relativistic particles was a common feature of active galaxies (Burbidge, Burbidge and Sandage 1963).

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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