Astronomical Observatory ZRiFK

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Cosmic rays and magnetic fields in clusters of galaxies

Beyond the thermal aspect, the galaxy cluster physics is based on cosmic rays injection and transport processes followed by nonthermal radiative processes.The information about these nonequilibrium processes is encoded in the spectral and spatial distribution of of cosmic ray electrons and protons. The intracluster medium study requires a complex description, simultaneously explaining the relevant physical processes e.g. cosmic rays and plasma interaction, cooling and heating mechanism, the role of shock waves and plasma turbulences and the origin of intracluster magnetic field.

The main scientific issues:

  • Studies of extended diffused cluster radio emission are confronted with models on the origin and amplification of cluster magnetic fields as well as current knowledge on the production/acceleration of relativistic electrons and protons.

    • G. Siemieniec, A. Woszczyna Magnetized Cosmic Walls, 2004, A&A, 414, 1
    • G. Siemieniec, Z. Golda Magnetic Amplification in Cylindrical Cosmological Structure, 2004, A&A, 422, 23
    • G. Siemieniec Spatial energy spectrum of primordial magnetic field, 2005, A&A, 429, 785
    • G. Siemieniec Nonlinear amplification of the magnetized pancakes, 2006, AN, 327, 426
  • Current observational results suggest strong connections between the physical properties of radio halos and X-ray properties of clusters. The primary task is to understand the close similarity of the morphology of radio halos and the X-ray emission of their host clusters.The multifrequency observations are needed to explain the anticipated correlation with other spectral domains.

    • G. Siemieniec A study of the diffusive shock acceleration as a process explaining observations of 1 E0657-56 galaxy cluster 2004, Acta Phys. Polon. B, 35, 2131
  • Measurements of synchrotron radio emission at several frequencies usually provide the first evidence for the presence of a significant population of relativistic electrons and magnetic fields. Radio and also nonthermal X-ray observations provide an independent quantitative measures of very appreciable magnetic fields and relativistic electron densities in the observed clusters. These results open a new dimension in the study of clusters including prospects for the detection of gamma-ray emission. To identify the nonthermal processes (Inverse Compton, Bremsstrahlung, synchrotron) correctly we focus first on cosmic rays acceleration mechanisms in cluster mergers.

    • M. Ostrowski, G. Siemieniec Diffision in Momentum Space as a Picture of 2-nd order Fermi Acceleration 1997, Astroparticle Phys. 6, 271
    • G. Siemieniec, G. MichaƂek, M. Ostrowski Asymmetric Scattering of Energetic Particles by Finite Amplitude of Circularly Polarized Alfven Waves 1999, Astroparticle Phys. 10, 121
    • M. Ostrowski, G. Siemieniec On Energy Spectrum of UHE CR Accelerated in Supergalactic Accretion Flow A&A 2000, 355, 51
    • G. Siemieniec Stochastic Fermi Acceleration in Turbulent Fields With Non-Vanishing Wave Helicities 2002, Astroparticle Physics 16, 425
    • M. Ostrowski, G. Siemieniec Cosmic Ray Acceleration at Supergalactic Accretion, Shock: a New Upper Limit due to Finite Shock Extension 2001, A&A, 386, 829
  • The search of polarized emission in intracluster medium is aimed to indicate the regions of large-scale ordered magnetic field and to reconcile its generation mechanism with cosmic plasma modelling.

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