WAVELET TRANSFORM ANALYSIS OF THE SMALL-SCALE X-RAY STRUCTURE OF THE CLUSTER ABELL-1367

We have developed a new technique based on a wavelet transform analysi s to quantify the small-scale (less than a few arcminutes) X-ray struc ture of clusters of galaxies. We apply this technique to the ROSAT pos ition sensitive proportional counter (PSPC) and Einstein high-resoluti on imager (HRI) images of the central region of the cluster Abell 1367 to detect sources embedded within the diffuse intracluster medium. In addition to detecting sources and determining their fluxes and positi ons, we show that the wavelet analysis allows a characterization of th e source extents. In particular, the wavelet scale at which a given so urce achieves a maximum signal-to-noise ratio in the wavelet images pr ovides an estimate of the angular extent of the source. To account for the widely varying point response of the ROSAT PSPC as a function of off-axis angle requires a quantitative measurement of the source size and a comparison to a calibration derived from the analysis of a Deep Survey image. Therefore, we assumed that each source could be describe d as an isotropic two-dimensional Gaussian and used the wavelet amplit udes, at different scales, to determine the equivalent Gaussian FWHM ( and its uncertainty) appropriate for each source. In our analysis of t he ROSAT PSPC image, we detect 31 X-ray sources above the diffuse clus ter emission (within a radius of 24'), 16 of which are apparently asso ciated with cluster galaxies and two with serendipitous, background qu asars. We find that the angular extents of 11 sources exceed the nomin al width of the PSPC point-spread function. Four of these extended sou rces were previously detected by Bechtold et al. (1983) as 1'' scale f eatures using the Einstein HRI. The same wavelet analysis technique wa s applied to the Einstein HRI image. We detect 28 sources in the HRI i mage, of which nine are extended. Eight of the extended sources corres pond to sources previously detected by Bechtold et al. Overall, using both the PSPC and the HRI observations, we detect 16 extended features , of which nine have galaxies coincident with the X-ray-measured posit ions (within the positional error circles). These extended sources hav e luminosities lying in the range (3-30) x 10(40) ergs s(-1) and gas m asses of approximately (1-30) x 10(9) M., if the X-rays are of thermal origin. We confirm the presence of extended features in A1367 first r eported by Bechtold ct al. (1983). The nature of these systems remains uncertain. The luminosities are large if the emission is attributed t o single galaxies, and several of the extended features have no associ ated galaxy counterparts. The extended features may be associated with galaxy groups, as suggested by Canizares, Fabbiano, and Trinchieri (1 987), although the number required is large.