Synchrotron Self-Comptonized Emission of Low Energy Cosmic Ray Electrons in the Universe: I) Individual Sources

Abstract

Most of the Universe's populations of low energy cosmic ray electrons in the energy range of 1-100 MeV still manage to elude from detection by our instruments, since their synchrotron emission is at too low frequencies. We investigate a mechanism which can lead to observable emission of such electron populations: synchrotron-self Comptonization (SSC). The inverse Compton (IC) scattering can shift an otherwise unobservable low-frequency 10 kHz-10 MHz photons into observable radio, infrared (IR) or even more energetic wave-bands. The resulting emission should be polarized. We also consider IC scattering of the cosmic microwave background (CMB) and the cosmic radio background (CRB). Electron spectral aging due to synchrotron, IC and adiabatic losses or gains influences the resulting spectrum. The predicted radiation spectrum is a strong function of the history of the source, of the low energy spectrum of relativistic electrons, and of redshift. It has typically two maxima, and a decrement in between at CMB frequencies. Detection will give a sensitive probe of the environment of radio galaxies. We demonstrate that the fossil remnants of powerful radio galaxies are promising detection candidates, especially when they are embedded in a dense intra-cluster medium (ICM). GHz peaked sources (GPS) have very low SSC luminosities, which may, however, extend into the X-ray or even the gamma ray regime. Clusters of galaxies with relativistic electron populations may be another detectable sources. Fossil radio plasma released by our own Galaxy could be revealed by its large angular scale SSC flux. We discuss the expected detectability of these sources with new and upcoming instruments as LOFAR, GMRT, EVLA, ATA, ALMA, PLANCK, and HERSCHEL.

17 pages, 14 figures, accepted by Astronomy & Astrophysics, some changes due to referee's comments, new section about detectability

References in corpus (4)

• On The Non Thermal Emission and Acceleration of Electrons in Coma and Other Clusters of Galaxies
• Four Extreme Relic Radio Sources in Clusters of Galaxies
• A Chandra detection of the radio hotspot of 3C123
• Discovery of depressions in the X-ray emission of the distant galaxy cluster RBS797 in a CHANDRA observation

Cited by in corpus (5)

• Giant radio relics in galaxy clusters: reacceleration of fossil relativistic electrons?
• Radio and X-Ray Detectability of Buoyant Radio Plasma Bubbles in Clusters of Galaxies
• On the non-thermal high energy radiation of galaxy clusters
• On the escape of cosmic rays from radio galaxy cocoons
• Inverse-Compton Emission from Clusters of Galaxies: Predictions for ASTRO-H