Magnetic Field Configuration at the Galactic Center Investigated by Wide Field Near-Infrared Polarimetry

Shogo Nishiyama(1,2), Motohide Tamura(2), Hirofumi Hatano(3), Saori Kanai(3), Mikio Kurita(3), Shuji Sato(3), Noriyuki Matsunaga(1), Tetsuya Nagata(1), Takahiro Nagayama(1), Ryo Kandori(2), Yasushi Nakajima(2), Nobuhiko Kusakabe(4), Yaeko Sato(4), James H. Hough(5), Koji Sugitani(6), and Haruyuki Okuda(7)

(1) Department of Astronomy, Kyoto University, Kyoto 606-8502, Japan
(2)National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan
(3) Department of Astrophysics, Nagoya University, Nagoya 464-8602, Japan
(4) Department of Astronomical Sciences, Graduate University for Advanced Studies (Sokendai), Mitaka, Tokyo 181-8588, Japan
(5) Centre for Astrophysics Research, University of Hertfordshire, Hatfield, Herts AL10 9AB, UK
(6) Graduate School of Natural Sciences, Nagoya City University, Nagoya 467-8501, Japan
(7) Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Kanagawa 229-8510, Japan

Paper: ApJ, accepted


EPrint Server: 0809.3089


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 DEGr, 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.

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