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

TL;DR

This study uses near-infrared polarimetry to map the magnetic field structure at the Galactic center, revealing a predominantly toroidal magnetic configuration aligned with the Galactic plane.

Contribution

First to utilize wide-field near-infrared polarimetry to directly investigate the magnetic field structure at the Galactic center, confirming its toroidal nature.

Findings

Magnetic field aligned nearly parallel to the Galactic plane.

Polarization measurements consistent with far-infrared/submillimeter observations.

Foreground component subtraction enables direct study of the Galactic center magnetic field.

Abstract

We present a polarimetric map of a 20'x20' 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 about 20 deg, 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.