Spectral index map (central) between 141 MHz and 1.4 GHz at the resolution of 46″. The cutout images show the distribution of spectral indices between 141 MHz and 1.5 GHz at 16″ resolution. The LOFAR contour levels are ±[1, 2, 4, 8, 16] × 3σ, where σ = 345 μJy beam⁻¹ (beam_FWHM = 46″) and σ = 190 μJy beam⁻¹ (beam_FWHM = 16″) for the central and the cutout images, respectively. The corresponding maps for the spectral index errors are presented in Appendix C.