PUB - Publikationen an der Universität Bielefeld

We investigate the contribution that a local over- or under-density can haveon linear cosmic dipole estimations. We focus here on radio surveys, such asthe NRAO VLA Sky Survey (NVSS), and forthcoming surveys such as those with theLOw Frequency ARray (LOFAR), the Australian Square Kilometre Array Pathfinder(ASKAP) and the Square Kilometre Array (SKA). The NVSS has already been used toestimate the cosmic radio dipole; it was shown recently that this radio dipoleamplitude is larger than expected from a purely kinematic effect, assuming thevelocity inferred from the dipole of the cosmic microwave background. We showhere that a significant contribution to this excess could come from a localvoid or similar structure. In contrast to the kinetic contribution to the radiodipole, the structure dipole depends on the flux threshold of the survey andthe wave band, which opens the chance to distinguish the two contributions.