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For refcode 1995ApJ...445..607G:
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1995ApJ...445..607G WAVELET TRANSFORM ANALYSIS OF THE SMALL-SCALE X-RAY STRUCTURE OF THE CLUSTER ABELL 1367 S. A. GREBENEV Space Research Institute, Russian Academy of Sciences, 84/32 Profsoyuznaya, 117810 Moscow, Russia AND W. FORMAN, C. JONES, AND S. MURRAY Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 Received 1994 June 13; accepted 1994 October 28 ABSTRACT We have developed a new technique based on a wavelet transform analysis to quantify the small-scale (less than a few arcminutes) X-ray structure of clusters of galaxies. We apply this technique to the ROSAT position sensitive proportional counter (PSPC) and Einstein high- resolution imager (HRI) images of the central region of the cluster Abell 367 to detect sources embedded within the diffuse intracluster medium. In addition to detecting sources and determining their fluxes and positions, we show that the wavelet analysis allows a characterization of the source extents. In particular, the wavelet scale at which a given source achieves a maximum signal-to-noise ratio in the wavelet images provides 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 described as an isotropic two-dimensional Gaussian and used the wavelet amplitudes, at different scales, to determine the equivalent Gaussian FWHM (and its uncertainty) appropriate for each source. In our analysis of the ROSAT PSPC image, we detect 31 X-ray sources above the diffuse cluster emission (within a radius of 24'), 16 of which are apparently associated with cluster galaxies and two with serendipitous, background quasars. We find that the angular extents of 11 sources exceed the nominal width of the PSPC point-spread function. Four of these extended sources were previously detected by Bechtold et al. (1983) as 1" scale features using the Einstein HRI. The same wavelet analysis technique was applied to the Einstein HRI image. We detect 28 sources in the HRI image, of which nine are extended. Eight of the extended sources correspond 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 positions (within the positional error circles). These extended sources have luminosities lying in the range (3-30) x 10^40^ ergs s^-1^ and gas masses of approximately (1-30) x 10^9^ M_sun_, if the X-rays are of thermal origin. We confirm the presence of extended features in A1367 first reported by Bechtold et al. (1983). The nature of these systems remains uncertain. The luminosities are large if the emission is attributed to single galaxies, and several of the extended features have no associated galaxy counterparts. The extended features may be associated with galaxy groups, as suggested by Canizares, Fabbiano, & Trinchieri (1987), although the number required is large. Subject headings: galaxies: clusters: general - galaxies: clusters: individual (Abell 1367) - galaxies: structure - methods: data analysis - X-rays: galaxies
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