ESA Science & Technology - Improved sky reconstruction on NGC 4151

The sky region around the Seyfert-1 galaxy NGC 4151, with a total exposure time of 280 000 seconds. The image on the left has been reconstructed using the general method and exhibits strong contamination from systematic effects, manifested as the characteristic chessboard-like pattern of squares and ripples. The image on the right is, in contrast, a result using the improved new algorithm: all large-scale artefacts are removed, and the background sky is so clean that the detection of a new hard X-ray source, IGR J11203+4531 (highlighted by the green circle), becomes possible.

The angular size of each image is 30 x 30 square degrees.