A Wavelet Analysis Search for Substructures in Eleven X-Ray Clusters of Galaxies

We have searched for substructures at different scales on the images of eleven X-ray clusters of galaxies observed with the PSPC on the ROSAT satellite, using a method based on the wavelet transform. Such a hierarchical analysis is found to be very powerful to remove noise from images, compared to a Gaussian filtering, and to exhibit new fine structures at different scales even in well known clusters. We find that the distributions of the x-ray gas in the clusters ABCG 754 and ABCG 2256 exhibit very complex structures, with outstanding substructures at various scales. ABCG 401 also presents a complex structure, though somewhat less complicated than the previous two clusters. ABCG 3558 is found to be bimodal. Evidence for an offset between the x-ray centroid and the maximum x-ray emission is found for three other clusters (ABCG 483, 2218, and 4059). Three clusters only (ABCG 478, 1413, and 2029) out of eleven appear regular at all scales. A few implications on forecoming physical analyses are discussed.