Hardness ratio (0.3−0.7/1.0−8.0 keV) image. The clear stripe crossing the remnant from northeast to southwest follows those regions where the hardness ratio and the intervening absorption column are higher. White contours show the continuum at radio wavelengths that delineate the SNR shock front. The inset shows distribution of N_H integrated between 0 and 16.1 km s^-1, which is the systemic velocity of Puppis A. The HI data were obtained by Reynoso et al. (2003) (compare with Fig. 3 in D13).