Fig. 6.


Spectral index map of the peripheral emission between 143 MHz and 610 MHz at a resolution of 15′′ × 15′′ overlaid on the LOFAR contours of Fig. 4. Pixels with values below 3σ were blank. The corresponding error map is reported in Fig. A.1. The inset panel shows an SDSS image with two candidate optical counterparts.

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