Left: spectral index maps of the halo between 675 MHz and 1.5 GHz (top) and 675 MHz and 3.0 GHz (bottom) at 15″ resolution. The image properties are given in Table 2, IM3, IM7, and IM13. Contour levels are drawn at [1, 2, 4, 8, …] × 3.5 σ_rms, and are from the uGMRT Band 4 image. These maps show the presence of steeper spectral indices in outermost regions of the halo, in particular to the north. Right: corresponding spectral index uncertainty.