Astronomy & Astrophysics Seminar: Energetic Particles and Magnetic Fields in Galaxy Clusters

Abstract:

Measurements of extended regions of radio emission in many clusters provide direct evidence for intracluster (IC) relativistic electrons and magnetic fields, and indirectly also for energetic protons. This first tangible basis for determining nonthermal quantities in extragalactic environments can potentially yield important clues on their likely origin and their possible impact on thermal and dynamical properties of IC gas. Searches for X-ray emission by the radio-emitting electrons (mostly by Compton scattering off the CMB) have not yet resulted in high-significance detections. A model for IC particles and magnetic fields is formulated based on the expectation that these are of galactic origin, and that no re-acceleration or field amplification take place outside galaxies. In this approach the particles diffuse out of star-forming and radio galaxies and their spectro-spatial properties and radiative yields reflect solely the respective properties of their sources and spatial distributions of IC gas density and magnetic fields. Predictions of the model are contrasted with available radio, X-ray, and recent gamma-ray measurements by the Fermi satellite.

Seminar Organizer: Prof. Rennan Barkana