Search and analysis of small scale structures in two X-ray clusters of galaxies

Wepresentarenementofthewaveletanalysistech- nique for the detection and characterisation of small scale fea- tures embedded in a strongly varying background. This tech- nique handles with particular care the side effects of non- orthogonality in the wavelet space which can cause spurious detections and lead to a biased estimate of source parameters. This novel technique is applied to two ROSAT PSPC pointed observations of nearby clusters of galaxies, A 1367 and A 194. We nd evidence that the case of A 1367 is not unique and that galaxy-scale X-ray emission could be a quite common prop- erty of clusters of galaxies. We detect 28 sources in the eld of A 1367 and 26 in the eld of A 194. Since these numbers are signicantly larger than those expected from the logN logS relation in the eld, most of the sources are expected to be associated with the cluster itself and indeed several identica- tions with galaxies are possible. In addition, CCD observations have revealed that two X-ray sources in the eld of A 194, clas- sied as extended by the multi-scale analysis, are very likely associated with two background galaxy clusters at intermediate redshift.