Why can classification based on morphology be ambiguous for a single SNR structure?
Because the appearance depends on the observational wavelength; for example, radio contours might show a 'shell' while X-ray images show a 'filled-center' morphology.
A major factor complicating the labeling of Supernova Remnants is that their visual appearance is highly dependent on the wavelength used for observation. Different physical processes dominate emission across the spectrum. For instance, radio observations often highlight synchrotron radiation from the compressed shock boundary, clearly delineating a shell structure. However, an X-ray observation of the same object might show emission dominated by the thermal radiation from the very hot interior gas, resulting in a morphology described as 'filled-center.' This disparity means that morphological labels are descriptive tools based on a specific viewing angle or process, not definitive labels of the entire structure.
