Top left: GMRT 325 MHz map. Contour levels are drawn as in Fig. 1. Top middle: VLA 1425 MHz map. Contour levels are drawn as in Fig. 1. Top right: VLA 1425 MHz high-resolution image. The image was made using Briggs weighting with robust set to  −1. Contour levels are drawn at . Bottom left: spectral index map between 325 and 610 MHz at a resolution of 10.4″ × 7.7″. Contour levels are from the 325 MHz GMRT image and drawn at levels of  [1,2,4,8,...]     × 6σ_rms. Bottom middle: spectral index between 610 and 1425 MHz. Contour levels are from the 610 MHz GMRT image and drawn at levels of  [ 1,2,4,8,... ]     × 5σ_rms. The beam size is 6.41″ × 5.26″. Bottom right: spectral curvature map. Contour levels are drawn as in the left panel and the resolution is 10.4″ × 7.7″.