Imprint of Intergalactic Shocks on the Radio Sky

摘要: Strong intergalactic shocks are a natural consequence of structure formation in the universe. These expected to deposit large fractions their thermal energy relativistic electrons (ξe 0.05 according supernova remnant observations) and magnetic fields (ξB 0.01 cluster halo observations). We calculate synchrotron emission from such using an analytical model, calibrated verified based on hydrodynamic ΛCDM simulation. The resulting signal composes fraction (up few 10%) extragalactic radio background below 500 MHz. associated angular fluctuations, e.g., δTl 260(ξeξB/5 × 10-4)(ν/100 MHz)-3 K for multipoles 400 l 2000, dominate sky frequencies ν 10 GHz scales 1' θ < 1° (after modest removal discrete sources), provided that ξeξB 3 10-4. fluctuating is most pronounced MHz, dominating there even = 5 10-5. will be easily observable by next-generation telescopes as LOFAR SKA marginally with present-day telescopes. could also identified through cross-correlation tracers large-scale (such γ-ray shocks), possibly existing CMB anisotropy maps high-resolution ~1 surveys. Detection provide first identification warm-hot medium (believed contain baryons low-redshift universe), gauge unknown strength field. analyze observations diffuse MHz show they well fitted simple, double-disk Galactic precluding direct background. Modeling frequency-dependent pattern observed at very low (1-10 MHz) can used disentangle distributions cosmic rays, ionized gas, fields. Space missions Astronomical Low Frequency Array thus important insight into composition our Galaxy.