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RADIO EMISSION FROM WEAK SPHERICAL SHOCKS IN THE OUTSKIRTS OF GALAXY CLUSTERS
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 Title & Authors
RADIO EMISSION FROM WEAK SPHERICAL SHOCKS IN THE OUTSKIRTS OF GALAXY CLUSTERS
Kang, Hyesung;
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 Abstract
In Kang (2015) we calculated the acceleration of cosmic-ray electrons at weak spherical shocks that are expected to form in the cluster outskirts, and estimated the diffuse synchrotron radiation emitted by those electrons. There we demonstrated that, at decelerating spherical shocks, the volume integrated spectra of both electrons and radiation deviate significantly from the test-particle power-laws predicted for constant planar shocks, because the shock compression ratio and the flux of inject electrons decrease in time. In this study, we consider spherical blast waves propagating through a constant density core surrounded by an isothermal halo with ρ ∝ r−n in order to explore how the deceleration of the shock affects the radio emission from accelerated electrons. The surface brightness profile and the volumeintegrated radio spectrum of the model shocks are calculated by assuming a ribbon-like shock surface on a spherical shell and the associated downstream region of relativistic electrons. If the postshock magnetic field strength is about 0.7 or 7 µG, at the shock age of ∼ 50 Myr, the volume-integrated radio spectrum steepens gradually with the spectral index from αinj to αinj + 0.5 over 0.1–10 GHz, where αinj is the injection index at the shock position expected from the diffusive shock acceleration theory. Such gradual steepening could explain the curved radio spectrum of the radio relic in cluster A2266, which was interpreted as a broken power-law by Trasatti et al. (2015), if the relic shock is young enough so that the break frequency is around 1 GHz.
 Keywords
acceleration of particles;cosmic rays;galaxies: clusters: general;shock waves;
 Language
English
 Cited by
1.
RADIO AND X-RAY SHOCKS IN CLUSTERS OF GALAXIES, The Astrophysical Journal, 2015, 812, 1, 49  crossref(new windwow)
2.
LOFAR, VLA, ANDCHANDRAOBSERVATIONS OF THE TOOTHBRUSH GALAXY CLUSTER, The Astrophysical Journal, 2016, 818, 2, 204  crossref(new windwow)
3.
SuzakuX-ray study of the double radio relic galaxy cluster CIZA J2242.8+5301, Astronomy & Astrophysics, 2015, 582, A87  crossref(new windwow)
 References
1.
Bell, A. R. 1978, The Acceleration of Cosmic Rays in Shock Fronts. I, MNRAS, 182, 147 crossref(new window)

2.
Bell, A. R. 2004, Turbulent Amplification of Magnetic Field and Diffusive Shock Acceleration of Cosmic Rays, MNRAS, 353, 550 crossref(new window)

3.
Brüggen, M., Bykov, A., Ryu, D., & Röttgering, H. 2012, Magnetic Fields, Relativistic Particles, and Shock Waves in Cluster Outskirts Space Sci. Rev., 166, 187 crossref(new window)

4.
Brunetti, G., & Jones, T. W. 2014, Cosmic Rays in Galaxy Clusters and Their Nonthermal Emission, Int. J. of Modern Physics D, 23, 30007

5.
Caprioli, D., & Sptikovsky, A. 2014, Simulations of Ion Acceleration at Non-relativistic Shocks. II. Magnetic Field Amplification, ApJ, 794, 46 crossref(new window)

6.
Drury, L. O’C. 1983, An Introduction to the Theory of Diffusive Shock Acceleration of Energetic Particles in Tenuous Plasmas, Rept. Prog. Phys., 46, 973 crossref(new window)

7.
Feretti, L., Giovannini, G., Govoni, F., & Murgia, M. 2012, Clusters of Galaxies: Observational Properties of the Diffuse Radio Emission, A&A Rev., 20, 54

8.
Kang, H. 2011, Energy Spectrum of Nonthermal Electrons Accelerated at a Plane Shock, JKAS, 44, 49

9.
Kang, H. 2015, Nonthermal Radiation from Relativistic Electrons Accelerated at Spherically Expanding Shocks, JKAS, 48, 9

10.
Kang, H., & Jones, T. W. 2006, Numerical Studies of Diffusive Shock Acceleration at Spherical Shocks, Astropart. Phys., 25, 246 crossref(new window)

11.
Kang, H., Jones, T. W., & Gieseler, U. D. J. 2002, Numerical Studies of Cosmic-Ray Injection and Acceleration, ApJ, 579, 337 crossref(new window)

12.
Kang, H., Ryu, D., Cen, R., & Ostriker, J. P. 2007, Cosmological Shock Waves in the Large-Scale Structure of the Universe: Nongravitational Effects, ApJ, 669, 729 crossref(new window)

13.
Kang, H., Ryu, D., & Jones, T. W. 2012, Diffusive Shock Acceleration Simulations of Radio Relics, ApJ, 756, 97 crossref(new window)

14.
Lucek, S. G., & Bell, A. R. 2000, Non-Linear Amplification of a Magnetic Field Driven by Cosmic Ray Streaming, MNRAS, 314, 65 crossref(new window)

15.
Malkov M. A., & Drury, L. O’C. 2001, Nonlinear Theory of Diffusive Acceleration of Particles by Shock Waves, Rep. Progr. Phys., 64, 429 crossref(new window)

16.
Nuza, S. E., Hoeft, M., van Weeren, R. J., Gottlöber, S., & Yepes, G. 2012, How Many Radio Relics Await Discovery?, MNRAS, 420, 2006 crossref(new window)

17.
Ryu, D., Kang, H., Hallman, E., & Jones, T. W. 2003, Cosmological Shock Waves and Their Role in the Large-Scale Structure of the Universe, ApJ, 593, 599 crossref(new window)

18.
Sarazin, C. L. 1988, X-Ray Emission from Clusters of Galaxies (Cambridge: Cambridge University Press)

19.
Schlickeiser, R. 2002, Cosmic Ray Astrophysics (Berlin: Springer)

20.
Shimwell, T. W., Markevitch, M., Brown, S., Feretti, L, et al. 2015, Another Shock for the Bullet Cluster, and the Source of Seed Electrons for Radio Relics, MNRAS, 449, 1486 crossref(new window)

21.
Skilling, J. 1975, Cosmic Ray Streaming. I - Effect of Alfv´en Waves on Particles, MNRAS, 172, 557 crossref(new window)

22.
Skillman, S. W., Hallman, E. J., O’Shea, W., Burns, J. O., Smith, B. D., & Turk, M. J. 2011, Galaxy Cluster Radio Relics in Adaptive Mesh Refinement Cosmological Simulations: Relic Properties and Scaling Relationships, ApJ, 735, 96 crossref(new window)

23.
Stroe, A., Harwood, J. J., Hardcastle, M. J., & Rttgering, H. J. A. 2014, Spectral Age Modelling of the ‘Sausage’ Cluster Radio Relic, MNRAS, 455, 1213

24.
Trasatti, M., Akamatsu, H., Lovisari, L., Klein, U., Bonafede, A., Brggen, M., Dallacasa, D., & Clarke, T. 2015, The Radio Relic in Abell 2256: Overall Spectrum and Implications for Electron Acceleration, A&Ap, 575, A45

25.
van Weeren, R., Röttgering, H. J. A., Brüggen, M., & Hoeft, M. 2010, Particle Acceleration on Megaparsec Scales in a Merging Galaxy Cluster, Science, 330, 347 crossref(new window)

26.
van Weeren, R., Hoeft, M., Röttgering, H. J. A., Brüggen, M., Intema, H. T., & van Velzen, S. 2011, A Double Radio Relic in the Merging Galaxy Cluster ZwCl 0008.8+5215, A&AP, 528, A38

27.
van Weeren, R., Röttgering, H. J. A., Intema, H. T., Rudnick, L., Brüggen, M., Hoeft, M., & Oonk, J. B. R. 2012, The “Toothbrush-Relic”: Evidence for a Coherent Linear 2-Mpc Scale Shock Wave in a Massive Merging Galaxy Cluster?, A&AP, 546, 124 crossref(new window)

28.
Vazza, F., Brunetti, G., & Gheller, C. 2009, Shock Waves in Eulerian Cosmological Simulations: Main Properties and Acceleration of Cosmic Rays, MNRAS, 395, 1333 crossref(new window)

29.
Vazza, F., Bruggen, M., Gheller, C., & Brunetti, G., 2012, Modelling Injection and Feedback of Cosmic Rays in Grid-Based Cosmological Simulations: Effects on Cluster Outskirts, MNRAS, 421, 3375 crossref(new window)