New λ6 cm observations of the Cygnus Loop

Radio continuum and polarization observations of the entire Cygnus Loop at lambda 6 cm wavelength were made with the Urumqi 25 m telescope. The lambda 6 cm map is analysed together with recently published maps from the Effelsberg 100 m telescope at lambda 21 cm and lambda 11 cm. The integrated flux density of the Cygnus Loop at lambda 6 cm is 90 +/- 9 Jy, which implies a spectral index of alpha = -0.40 +/- 0.06. This rules out any global spectral steepening up to lambda 6 cm. However, small spectral index variations in some regions of the source are possible, but there are no indications for any spectral curvature. The linear polarization data at lambda 6 cm show percentage polarizations up to 35% in some areas of the Cygnus Loop, exceeding those observed at lambda 11 cm. The Rotation Measure is around -21 rad m(-2) in the southern area, which agrees with previous observations. However, the distribution of Rotation Measures is rather complex in the northern part of the Cygnus Loop, where the lambda 21 cm emission is totally depolarized. Rotation Measures based on lambda 11 cm and lambda 6 cm data are significantly larger than in the southern part. The difference in the polarization characteristics between the northern and southern part supports previous ideas that the Cygnus Loop consists of two supernova remnants.