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Astronomy Journal Article Extract, Edited Version

Here wWe useapply, for the first time, the Cappellari & Copin (2003; hereafter CC03) Voronoi tesselation algorithm (hereafter VT) to build the XMM EPIC temperature map of A3266. This is the first time that this algorithm has been applied to XMM data We first extracted source and background images in the 0.5-7.5 keV energy band,. The chosen energy range optimizingses the contrast between cluster signal andover the particle background inover the temperature range of the cluster. These two images arewere then used to estimate the Signal-to-Noise (S/N) of each pixel.

We were unable to use the CC03 algorithm in a single step, sinceAs X-ray events are distributed following a Poisson distribution statistics and, many of the pixels have a low S/N and it is therefore inappropriate to apply the CC03 algorithm directly to our data. Our implementation of the algorithm thus involves two steps. We first selected only those all the pixels with a sufficiently high S/N (i.e. (S–N)/N ≥ 1.05) and used the CC03 algorithm to bin themse pixels into meta-pixel groups with a S/N ~ 130 (our final goal for the temperature map). Since these meta-pixels weare obtained from athe high S/N subset, they are not generated from a continuous set of pixelsregion. In tThe second step, we consists of assigning alleach of the so-far unbinned pixels to theirits closest meta-pixel. Obviously, the addition of theseWhile including the lower S/N pixels clearly increases the adds scatter to the S/N of the final distribution of the meta-pixels. S/N distribution, However, the resulting distributionset of convex meta-pixel s (cells) covers the whole image without significantly degrading the overall S/N.

In applyingApplication of this technique to the A3266 mosaic event list, of A3266 results inwe obtain a total of 138 cells. We fitted the spectrum of each cell with an absorbed mekal model to the spectrum of each cell using XSPEC v11.2. Note: you fit a model to the data, not the other way around. The absorption iswas fixed to the Galactic value (NH = 1.6×1020 cm-2; Dickey & Lockman 1990), and the abundances arewere fixed to 0.2 Z/Zsol=0.2. This abundance value wasis obtained by fitting a a two-temperature mekal model with a single abundance to the global spectrum, extracted within a circle of 10 arcmin and excluding point sources, with a two-temperature mekal model with abundances tied together. Our best fitting global abundance is in reasonable agreement with the value found by Henriksen & Tittley (2002) in the central region mapped by Chandra (see also De Grandi & Molendi, 1999). We note that a single temperature model iprovides an acceptable fit to alleach of the 138 cells spectra.