The search for X-ray emission from electron/positron pair halos using the XMM-Newton observatory

Abstract

An electron/positron pair halo is formed by electromagnetic cascades that initiate when high energy gamma-rays from extragalactic sources - i.e. Blazar AGN - interact with the cosmic infrared background (CIB), and are then absorbed via the electron/positron pair production process. The high energy electron/positron pairs produced could up-scatter the cosmic microwave background (CMB) and become gamma rays which can interact with CIB again. Thus, the process could happen continuously until the produced gamma-rays have insufficient energy to interact with the CIB. Indeed, given the presence of intergalactic magnetic field, the produced electron/positron pairs could gyrate before scattered with the CMB photons so that they emit X-ray photons via the synchrotron radiation process. In this work, we determine whether the predicted X-ray photons emitted from the halo can be detected by the current generation X-ray observatory: XMM-Newton. The Spectral Energy Distributions (SEDs) of the synchrotron radiation of the pair halo predicted to be obtained from the AGN H1426+428 are simulated by the Monte Carlo simulations method; these are used as a source model for simulating observed spectra. The spectra of the halo virtually observed by XMM-Newton are generated in three different regions: the inner region, outer region and the region out of the XMM-Newton's field of view. The resulting spectra suggest that the outer region spectra could provide the best opportunity to detect and confirm the existence of electron/positron pair halos. © Published under licence by IOP Publishing Ltd.