Polarized intensity maps with overlaid Stokes I contours (green) and Faraday spectra of the LOFAR detected polarized sources. The orange and yellow circles in the bottom left corners represent the synthesized beam of the observations in polarization (20′′) and in Stokes I (6′′), respectively. The Stokes I contours start either at 55σ_I or 20σ_I and increase by factors of two, or at 10σ_I and increase by factors of (see text for details). The blue square and red circle plotted on some of the polarized intensity maps represent the locations of the polarized sources detected at 1.4 GHz by Taylor et al. (2007) and Grant et al. (2010), respectively. The dashed and dotted red horizontal lines plotted on the Faraday spectra represent the 3σ_QU and 8σ_QU levels, respectively. The vertical gray area encloses the excluded area in Faraday depth to avoid instrumental polarization leakage, sometimes visible as lesser peaks within this range.