Spectral index maps of the central region of Abell 1775. Upper panel: Spectral index maps of 6″ × 6″ resolution radio images. Left: Low-frequency spectral index map between LOFAR and uGMRT band 3. Right: High-frequency map between uGMRT band 3 and 4. Bottom panel: Spectral index maps at 15″ × 15″ resolution for both low (on the left) and high frequency (on the right). All images are overlaid with LOFAR contours of 15″ resolution. The beam size and the scale bar are indicated in all images.