A Sino-German λ6 cm polarization survey of the Galactic plane

IV. The region from 60° to 129° longitude

¹ National Astronomical Observatories, Chinese Academy of Sciences, Jia-20, Datun Road, Chaoyang District, Beijing 100012, PR China
e-mail: hjl@bao.ac.cn
² Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany

Received: 29 November 2010
Accepted: 25 January 2011

Abstract

Context. Linear polarization of diffuse Galactic emission is a signature of magnetic fields in the interstellar medium of our Galaxy. Observations at high frequencies are less affected by Faraday depolarization than those at lower frequencies and are able to detect polarized emission from more distant Galactic regions.

Aims. We attempt to perform a sensitive survey of the polarized emission from the Galactic disk at λ6 cm wavelength.

Methods. We made polarization observations of the Galactic plane using the Urumqi 25-m telescope at λ6 cm covering the area of 60° ≤ l ≤ 129° and  |b|  ≤ 5°. Missing large-scale structures in polarization were restored by extrapolation of the WMAP polarization data.

Results. We present λ6 cm total intensity and linear polarization maps of the surveyed region. We identify two new extended H ii regions G98.3 − 1.6 and G119.6+0.4 in this region. Numerous polarized patches and depolarization structures are visible in the polarization maps. Depolarization along the periphery of a few H ii complexes was detected and can be explained by a Faraday screen model. We discuss some prominent depolarization H ii regions, which have regular magnetic fields of several μG. Structure functions of U, Q, and PI images of the entire λ6 cm survey region of 10° ≤ l ≤ 230° exhibit much larger fluctuation power towards the inner Galaxy, which suggests a higher turbulence in the arm regions of the inner Galaxy.

Conclusions. The Sino-German λ6 cm survey reveals new properties of the diffuse magnetized interstellar medium. The survey is also very useful for studying individual objects such as H ii regions, which may act as Faraday screens with high rotation measures and strong regular magnetic fields inside.