Measuring the Magnetic Field and Relativistic Particles in Relic Radio Galaxies

We propose XMM observations of four relic radio galaxies, withthe goal of detecting inverse Compton scattered microwavebackground radiation. Detection of this emission would yieldboth a measurement of the relativistic electron density andthe magnetic field, directly testing assumptions of equipartition,and providing a unique probe of conditions in the surrounding IGM.XMM.s high sensitivity and broad bandpass are ideally suitedto these observations. Nondetection by XMM would imply extremedepartures of the particles and fields from equipartition, itselfa surprising and important result. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]