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
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.
Preprints available from the authors at firstname.lastname@example.org
or the raw TeX (no figures) if you click here.
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