Magnetic field configuration at the galactic center investigated by wide-field near-infrared polarimetry : transition from a toroidal to a poloidal magnetic field

We present a large-scale view of the magnetic field (MF) in the central 2° × 2° region of our Galaxy. The polarization of point sources has been measured in the J, H, and KS bands using the near-infrared polarimetric camera SIRPOL on the 1.4 m Infrared Survey Facility telescope. Comparing the Stokes parameters between high extinction stars and relatively low extinction ones, we obtain polarization originating from magnetically aligned dust grains in the central few hundred parsecs of our Galaxy. We find that near the Galactic plane, the MF is almost parallel to the Galactic plane (i.e., toroidal configuration), but at high Galactic latitudes (b >04) the field is nearly perpendicular to the plane (i.e., poloidal configuration). This is the first detection of a smooth transition of the large-scale MF configuration in this region. [see original online version for correct notation]