Combined SUMSS at 843 MHz (red), 1.3–1.5 keV eRASS:4 (green), and 1.7–1.9 keV eRASS:4 (blue) image at and around the SNR G309.8+00.0 location. A spectrally motivated selection of X-ray narrow energy ranges was made to demonstrate the spatial distribution of Mg XI+XII and Si XIII emission lines across the remnant’s area. A linear color distribution is used for all three image components. The radio and X-ray components of this sky map were constructed using an identical approach in terms of pixel size, smoothing, and point source removal as described in the caption of Fig. 1.