scholarly journals Multi-Messenger Studies of Cosmic-Ray Acceleration in Galaxy Cluster Accretion Shocks

2020 ◽  
Author(s):  
Aleksandra Aleksandra Ciprijanovic
Keyword(s):  
Galaxy Cluster ◽  
Cosmic Ray ◽  
Cosmic Ray Acceleration ◽  
Accretion Shocks

scholarly journals Reaching thermal noise at ultra-low radio frequencies

2020 ◽  
Vol 642 ◽  
pp. A85 ◽  
Author(s):  
F. de Gasperin ◽  
G. Brunetti ◽  
M. Brüggen ◽  
R. van Weeren ◽  
W. L. Williams ◽  
...  
Keyword(s):  
Thermal Noise ◽  
Signal To Noise Ratio ◽  
Low Frequency ◽  
Galaxy Cluster ◽  
Cosmic Ray ◽  
Radio Halo ◽  
Cosmic Ray Acceleration ◽  
The Galaxy ◽  
Background Turbulence ◽  
Post Shock

Context. Ultra-low frequency observations (< 100 MHz) are particularly challenging because they are usually performed in a low signal-to-noise ratio regime due to the high sky temperature and because of ionospheric disturbances whose effects are inversely proportional to the observing frequency. Nonetheless, these observations are crucial for studying the emission from low-energy populations of cosmic rays. Aims. We aim to obtain the first thermal-noise limited (∼1.5 mJy beam−1) deep continuum radio map using the Low Frequency Array’s Low Band Antenna (LOFAR LBA) system. Our demonstration observation targeted the galaxy cluster RX J0603.3+4214 (known as the Toothbrush cluster). We used the resulting ultra-low frequency (39–78 MHz) image to study cosmic-ray acceleration and evolution in the post shock region considering the presence of a radio halo. Methods. We describe the data reduction we used to calibrate LOFAR LBA observations. The resulting image was combined with observations at higher frequencies (LOFAR 150 MHz and VLA 1500 MHz) to extract spectral information. Results. We obtained the first thermal-noise limited image from an observation carried out with the LOFAR LBA system using all Dutch stations at a central frequency of 58 MHz. With eight hours of data, we reached an rms noise of 1.3 mJy beam−1 at a resolution of 18″ × 11″. Conclusions. The procedure we developed is an important step towards routine high-fidelity imaging with the LOFAR LBA. The analysis of the radio spectra shows that the radio relic extends to distances of 800 kpc downstream from the shock front, larger than what is allowed by electron cooling time. Furthermore, the shock wave started accelerating electrons already at a projected distance of < 300 kpc from the crossing point of the two clusters. These results may be explained by electrons being re-accelerated downstream by background turbulence, possibly combined with projection effects with respect to the radio halo.

Cosmic-ray acceleration by pulsars

1984 ◽  
Vol 4 (2-3) ◽  
pp. 387-391 ◽  
Author(s):  
F.Curtis Michel
Keyword(s):  
Cosmic Ray ◽  
Cosmic Ray Acceleration

Supernova Remnants: An Introductory Review

2004 ◽  
Vol 218 ◽  
pp. 57-64
Author(s):  
Jacco Vink
Keyword(s):  
Cosmic Rays ◽  
Supernova Remnants ◽  
Supernova Remnant ◽  
Cosmic Ray ◽  
Recent Advances ◽  
Cosmic Ray Acceleration ◽  
Introductory Review

The two main aspects of supernova remnant research addressed in this review are: I. What is our understanding of the progenitors of the observed remnants, and what have we learned from these remnants about supernova nucleosynthesis? II. Supernova remnants are probably the major source of cosmic rays. What are the recent advances in the observational aspects of cosmic ray acceleration in supernova remnants?

scholarly journals Multiwavelength Signatures of Cosmic Ray Acceleration by Young Supernova Remnants

2008 ◽  
Author(s):  
Jacco Vink ◽  
Felix A. Aharonian ◽  
Werner Hofmann ◽  
Frank Rieger
Keyword(s):  
Supernova Remnants ◽  
Cosmic Ray ◽  
Cosmic Ray Acceleration
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