A Sino-German 6cm polarization survey of the Galactic plane IV. The region from 60deg to 129deg longitude

TL;DR

This paper presents a high-sensitivity 6cm polarization survey of the Galactic plane, revealing new HII regions, depolarization structures, and insights into magnetic field turbulence and interstellar medium properties.

Contribution

It provides the first detailed 6cm polarization maps of the specified Galactic region, identifying new HII regions and analyzing magnetic field structures and turbulence.

Findings

Discovery of two new extended HII regions G98.3-1.6 and G119.6+0.4.

Detection of numerous polarized patches and depolarization structures.

Larger fluctuation power in the inner Galaxy indicating higher turbulence.

Abstract

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. We attempt to perform a sensitive survey of the polarized emission from the Galactic disk at 6 cm wavelength. We made polarization observations of the Galactic plane using the Urumqi 25-m telescope at 6 cm covering the area of 60deg< l <129deg and |b|<5deg. Missing large-scale structures in polarization were restored by extrapolation of the WMAP polarization data. We present the 6cm total intensity and linear polarization maps of the surveyed region. We identify two new extended HII 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 HII complexes was detected and can be explained by a Faraday screen model. We discuss some prominent depolarization HII regions, which have regular magnetic fields of several $\mu$G. Structure functions of U, Q and PI images of the entire 6cm survey region of 10deg< l < 230deg exhibit much larger fluctuation power towards the inner Galaxy, which suggests a higher turbulence in the arm regions of the inner Galaxy. The Sino-German 6cm survey reveals new properties of the diffuse magnetized interstellar medium. The survey is also very useful for studying individual objects such as HII regions, which act as Faraday screens and have high rotation measures and therefore strong regular magnetic fields inside the regions.