MAGNETIC FIELD CONFIGURATION AT THE GALACTIC CENTER INVESTIGATED BY WIDE FIELD NEAR-INFRARED POLARIMETRY

Abstract

We present a polarimetric map of a 20' × 20' area toward the Galactic center. 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 telescope IRSF. One percent or better accuracy of polarization degree is achieved for sources with J < 14.5, H < 13.5, and KS < 12.0. Comparing the Stokes parameters between high extinction stars and relatively low extinction ones, we have obtained a polarization originating from magnetically aligned dust grains at the central region of our Galaxy of at most 1–2 kpc. The distribution of the position angles shows a peak at ∼20°, nearly parallel to the Galactic plane, suggesting a toroidal magnetic configuration. The derived direction of the magnetic field is in good agreement with that obtained from far-infrared/submillimeter observations, which detect polarized thermal emission from dust in the molecular clouds at the Galactic center. Our results show that, by subtracting foreground components, near-infrared polarimetry allows investigation of the magnetic field structure at the Galactic center.