scholarly journals Modelling of synchrotron emission from galaxies and extragalactic radio background

2020 ◽  
Author(s):  
Nomthendeleko Motha ◽  
Soebur Razzaque
Keyword(s):  
Synchrotron Emission ◽  
Radio Background

scholarly journals Fluctuations in the Radio Background from Intergalactic Synchrotron Emission

2000 ◽  
Vol 545 (1) ◽  
pp. L11-L14 ◽  
Author(s):  
Eli Waxman ◽  
Abraham Loeb
Keyword(s):  
Synchrotron Emission ◽  
Radio Background

Simulated synchrotron emission for the Tycho’s supernova remnants: an asymmetric initial mass model

2020 ◽  
Vol 494 (2) ◽  
pp. 1531-1538
Author(s):  
A Moranchel-Basurto ◽  
P F Velázquez ◽  
G Ares de Parga ◽  
E M Reynoso ◽  
E M Schneiter ◽  
...  
Keyword(s):  
Supernova Remnants ◽  
Brightness Distribution ◽  
Radio Continuum ◽  
Initial Mass ◽  
Continuum Emission ◽  
Synchrotron Emission ◽  
Mass Model ◽  
Mhd Simulations ◽  
Tycho’S Snr ◽  
Good Agreement

ABSTRACT We have performed 3D magnetohydrodynamics (MHD) numerical simulations with the aim of exploring the scenario in which the initial mass distribution of a supernova (SN) explosion is anisotropic. The purpose is to analyse if this scenario can also explain the radio-continuum emission and the expansion observed in young supernova remnants (SNRs). To study the expansion, synthetic polarized synchrotron emission maps were computed from the MHD simulations. We found a good agreement (under a number of assumptions) between this expansion study and previous observational results applied to Tycho’s SNR, which represents a good example of asymmetric young SNRs. Additionally, both the observed morphology and the brightness distribution are qualitatively reproduced.

scholarly journals Can the Local Bubble explain the radio background?

2021 ◽  
Vol 502 (2) ◽  
pp. 2807-2814
Author(s):  
Martin G H Krause ◽  
Martin J Hardcastle
Keyword(s):  
Magnetic Field ◽  
Energy Density ◽  
Radio Emission ◽  
Magnetic Energy ◽  
Cosmic Ray ◽  
Observational Constraints ◽  
Local Bubble ◽  
Magnetic Energy Density ◽  
Magnetic Field Model ◽  
Radio Background

ABSTRACT The ARCADE 2 balloon bolometer along with a number of other instruments have detected what appears to be a radio synchrotron background at frequencies below about 3 GHz. Neither extragalactic radio sources nor diffuse Galactic emission can currently account for this finding. We use the locally measured cosmic ray electron population, demodulated for effects of the Solar wind, and other observational constraints combined with a turbulent magnetic field model to predict the radio synchrotron emission for the Local Bubble. We find that the spectral index of the modelled radio emission is roughly consistent with the radio background. Our model can approximately reproduce the observed antenna temperatures for a mean magnetic field strength B between 3 and 5 nT. We argue that this would not violate observational constraints from pulsar measurements. However, the curvature in the predicted spectrum would mean that other, so far unknown sources would have to contribute below 100 MHz. Also, the magnetic energy density would then dominate over thermal and cosmic ray electron energy density, likely causing an inverse magnetic cascade with large variations of the radio emission in different sky directions as well as high polarization. We argue that this disagrees with several observations and thus that the magnetic field is probably much lower, quite possibly limited by equipartition with the energy density in relativistic or thermal particles (B = 0.2−0.6 nT). In the latter case, we predict a contribution of the Local Bubble to the unexplained radio background at most at the per cent level.

scholarly journals Spatiotemporal analysis of the runaway distribution function from synchrotron images in an ASDEX Upgrade disruption

2021 ◽  
Vol 87 (1) ◽  
Author(s):  
M. Hoppe ◽  
L. Hesslow ◽  
O. Embreus ◽  
L. Unnerfelt ◽  
G. Papp ◽  
...  
Keyword(s):  
Radial Profile ◽  
Spatiotemporal Analysis ◽  
High Energy ◽  
Synchrotron Emission ◽  
Analytic Model ◽  
Runaway Electrons ◽  
Radial Density ◽  
Radial Density Profile ◽  
Argon Injection ◽  
Seed Population

Synchrotron radiation images from runaway electrons (REs) in an ASDEX Upgrade discharge disrupted by argon injection are analysed using the synchrotron diagnostic tool Soft and coupled fluid-kinetic simulations. We show that the evolution of the runaway distribution is well described by an initial hot-tail seed population, which is accelerated to energies between 25–50 MeV during the current quench, together with an avalanche runaway tail which has an exponentially decreasing energy spectrum. We find that, although the avalanche component carries the vast majority of the current, it is the high-energy seed remnant that dominates synchrotron emission. With insights from the fluid-kinetic simulations, an analytic model for the evolution of the runaway seed component is developed and used to reconstruct the radial density profile of the RE beam. The analysis shows that the observed change of the synchrotron pattern from circular to crescent shape is caused by a rapid redistribution of the radial profile of the runaway density.

scholarly journals Quantiles as Robust Probes of Non-Gaussianity in 21-cm Images

2021 ◽  
Author(s):  
Alon Banet ◽  
Rennan Barkana ◽  
Anastasia Fialkov ◽  
Or Guttman
Keyword(s):  
Galactic Halo ◽  
Angular Resolution ◽  
Research Effort ◽  
First Stars ◽  
X Ray ◽  
Global Signal ◽  
Radio Background ◽  
Halo Masses ◽  
The Universe ◽  
Cosmic History

Abstract The epoch in which the first stars and galaxies formed is among the most exciting unexplored eras of the Universe. A major research effort is focused on probing this era with the 21-cm spectral line of hydrogen. While most research focuses on statistics like the 21-cm power spectrum or the sky-averaged global signal, there are other ways to analyze tomographic 21-cm maps, which may lead to novel insights. We suggest statistics based on quantiles as a method to probe non-Gaussianities of the 21-cm signal. We show that they can be used in particular to probe the variance, skewness, and kurtosis of the temperature distribution, but are more flexible and robust than these standard statistics. We test these statistics on a range of possible astrophysical models, including different galactic halo masses, star-formation efficiencies, and spectra of the X-ray heating sources, plus an exotic model with an excess early radio background. Simulating data with angular resolution and thermal noise as expected for the Square Kilometre Array (SKA), we conclude that these statistics can be measured out to redshifts above 20 and offer a promising statistical method for probing early cosmic history.

scholarly journals Synchrotron Emission from Particles Having A Truncated Power-law Energy Spectrum

1974 ◽  
Vol 168 (2) ◽  
pp. 379-397 ◽  
Author(s):  
L. J. Gleeson ◽  
M. P. C. Legg ◽  
K. C. Westfold
Keyword(s):  
Energy Spectrum ◽  
Power Law ◽  
Synchrotron Emission

scholarly journals The isotropic radio background revisited

2014 ◽  
Vol 2014 (04) ◽  
pp. 008-008 ◽  
Author(s):  
Nicolao Fornengo ◽  
Roberto A. Lineros ◽  
Marco Regis ◽  
Marco Taoso
Keyword(s):  
Radio Background

scholarly journals Thermalization of synchrotron radiation from field-aligned currents

1988 ◽  
Vol 6 (3) ◽  
pp. 493-501 ◽  
Author(s):  
William Peter ◽  
Anthony L. Peratt
Keyword(s):  
Magnetic Field ◽  
Synchrotron Radiation ◽  
Energy Density ◽  
Radiation Spectrum ◽  
Axial Magnetic Field ◽  
Three Dimensional ◽  
Synchrotron Emission ◽  
Microwave Background ◽  
Strong Function ◽  
Current Filaments

Three-dimensional plasma simulations of interacting galactic-dimensioned current filaments show bursts of synchroton radiation of energy density 1·2 ×10−13 erg/cm3 which can be compared with the measured cosmic microwave background energy density of 1·5 × 10−13 erg/cm3. However, the synchrotron emission observed in the simulations is not blackbody. In this paper, we analyze the absorption of the synchrotron emission by the current filaments themselves (i.e., self-absorption) in order to investigate the thermalization of the emitted radiation. It is found that a large number of current filaments (>1031) are needed to make the radiation spectrum blackbody up to the observed measured frequency of 100 GHz. The radiation spectrum and the required number of current filaments is a strong function of the axial magnetic field in the filaments.

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