A WAVELET ANALYSIS SEARCH FOR SUBSTRUCTURES IN 11 X-RAY-CLUSTERS OF GALAXIES

We have searched for substructures at different scales on the images o f eleven X-ray clusters of galaxies observed with the PSPC on the ROSA T satellite, using a method based on the wavelet transform. Such a hie rarchical analysis is found to be very powerful to remove noise from i mages, compared to a Gaussian filtering, and to exhibit new fine struc tures at different scales even in well known clusters. We find that th e distributions of the x-ray gas in the clusters ABCG 754 and ABCG 225 6 exhibit very complex structures, with outstanding substructures at v arious scales. ABCG 401 also presents a complex structure, though some what less complicated than the previous two clusters. ABCG 3558 is fou nd to be bimodal. Evidence for an offset between the x-ray centroid an d the maximum x-ray emission is found for three other dusters (ABCG 48 3, 2218, and 4059). Three clusters only (ABCG 478, 1413, and 2029) out of eleven appear regular at all scales. A few implications on forecom ing physical analyses are discussed.