Discovery of a Nonthermal Galactic Center Filament (G358.85+0.47) Parallel to the Galactic Plane

We report the discovery of a new non-thermal filament, G358.85+0.47, the``Pelican'', located ~225 pc in projection from SgrA, and oriented parallel tothe Galactic plane. VLA continuum observations at 20 cm reveal that this 7'(17.5 pc) structure bends at its northern extension and is comprised ofparallel strands, most apparent at its ends. Observations at 6 and 3.6 cmreveal that the Pelican is a synchrotron-emitting source and is stronglylinearly polarized over much of its extent. The spectral index of the filamentchanges from alpha(20/6)=-0.8 to alpha(6/3.6)=-1.5. The rotation measuresexhibit a smooth gradient, with values ranging from -1000 rad/m2 to +500rad/m2. The intrinsic magnetic field is well-aligned along the length of thefilament. Based on these properties, we classify the Pelican as one of thenon-thermal filaments unique to the Galactic center. Since these filaments(most of which are oriented perpendicular to the Galactic plane) are believedto trace the overall magnetic field in the inner Galaxy, the Pelican is thefirst detection of a component of this field parallel to the plane. The Pelicanmay thus mark a transition region of the magnetic field orientation in theinner kiloparsec of the Galaxy.Comment: 6 pages, 4 figures, to appear in ApJ Letters; Figs. 2 & 3 are color .ps files and best viewed in colo