Flat-fielded 3.5 × 2.4 degrees X-ray image of the Coma cluster. Flat-fielding procedure (see Eq. (1)) emphasizes departures from a smooth purely radial profile. The most spectacular is the bow-like sharp feature to the west of the core, which extends over ~ 3 Mpc from thenorth to the south. To the east of the core, there is another very sharp feature (~ 500 kpc in size), which turns out to be a contact discontinuity (see below). The NGC4839 (a dark spot to the SW from the core) appears to be connected with the main cluster via a rather faint “bridge.” In addition, one can spot a number of fainter filaments/extensions, which will be discussed in the forthcoming studies.