A new symmetrical polarization structure near the galactic centre

Filamentary radio structures perpendicular to the plane of the Galaxy and ∼30 pc away from the galactic centre ( l = 0.2) have been observed 1 . Here we present results showing a new region of polarized emission aligned with this Continuum Arc 1,2 . The structure of this region has the form of a central component (core) with two jet-like outer lobes. The associated total intensity maps at 4.75 and 10.7 GHz show that the core and lobes lie symmetrically with respect to arched filamentary structures lying both above and below the galactic plane—only the arches above the plane had been seen previously. The remarkable symmetry of the region suggests the location of a new ‘centre of activity’ within the galactic centre region at the position of the polarized core; however, total intensity maps do not distinguish this region at all except at low frequencies. A possible model involves outflow from the galactic nucleus to the vicinity of this new centre, explaining the polarization and low-frequency structure in terms of a ‘cocoon’ of thermal material surrounding the linear filaments seen in higher resolution studies. The regions of polarized emission then correspond to areas in which the cocoon is thinnest or absent.