Non-thermal radiation from intergalactic shocks

Uri Keshet (Weizmann Institute of Science) - MONDAY, Dec. 6 at 12:00 noon

Strong intergalactic shocks are a natural consequence of structure formation in the universe. Using analytic and numeric (SPH simulation based) analyses, we show that the non-thermal emission from such shocks produces a significant fraction of the extragalactic radio (ERB) and gamma-ray (EGRB) backgrounds, as well as anisotropy in the radio background that dominates on ~1-30 arcminute scales and low (<10 GHz) frequencies. We re-analyze existing gamma-ray and radio sky maps, finding that the EGRB is significantly lower than previously estimated, and ruling out previous claims for direct ERB detection. The predicted signals from intergalactic shocks should be detectable in the coming few years. For example, at least several gamma-ray clusters are predicted to be detectable by GLAST and by ground based Cherenkov telescopes, and the radio fluctuations are predicted to be detectable by LOFAR and by SKA. Detection of the signal will allow to identify intergalactic shocks and probe large-scale flows, will provide a direct detection of the warm-hot IGM, and may allow to determine the strength and structure of intergalactic magnetic fields.

The seminar will be held in 544 Campbell Hall.

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