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The XMM/2dF survey III: Comparison between optical and X-ray cluster detection methods

S. Basilakos·M. Plionis·A. Georgakakis·I. Georgantopoulos·T. Gaga·V. Kolokotronis·G. C. Stewart
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Abstract

We directly compare X-ray and optical techniques of cluster detection by combining SDSS photometric data with a wide-field ($\sim 1.8$ deg$^{2}$) XMM-{\em Newton} survey in the North Galactic Pole region. The optical cluster detection procedure is based on merging two independent selection methods - a smoothing+percolation technique, and a Matched Filter Algorithm. The X-ray cluster detection is based on a wavelet-based algorithm, incorporated in the SAS v.5.2 package. The final optical sample counts 9 candidate clusters with richness of more than 20 galaxies, corresponding roughly to APM richness class. Three, of our optically detected clusters are also detected in our X-ray survey. The most probable cause of the small number of optical cluster candidates detected in our X-ray survey is that they are relatively poor clusters, fainter than the X-ray flux limit (for extended sources) of our survey $f_{x}(0.3-2 {\rm keV}) \simeq 2 \times 10^{-14} erg cm^{-2} s^{-1}$.

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S. Basilakos, M. Plionis, A. Georgakakis, I. Georgantopoulos, T. Gaga, V. Kolokotronis, G. C. Stewart. 2004-03-16. The XMM/2dF survey III: Comparison between optical and X-ray cluster detection methods. https://doi.org/10.1111/j.1365-2966.2004.07841.x

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