Top panel: ROSAT PSPC map of photon counts in the 0.1−2.4 keV energy band in squared root scale. The bin size is 1′. The map was smoothed through the convolution with a Gaussian with σ = 3′ (3 pixel). The fil_all spectral region (see Fig. 5) is superimposed in blue. Center panel: ROSAT PSPC map of photon counts in the 0.3−0.5 keV energy band in squared root scale, smoothed with σ = 9′. The bin size is 3′. The red circle indicates the background spectrum region, and the black polygon is the filament spectrum extraction region. The fil_all spectral region is superimposed in blue. Bottom panel: ROSAT PSPC map of photon counts in the 0.5− 1.0 keV energy band in squared root scale, smoothed with σ = 9′. The bin size is 3′.