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Euclid preparation : III. Galaxy cluster detection in the wide photometric survey, performance and algorithm selection.

Adam, R. and Vannier, M. and Maurogordato, S. and Biviano, A. and Adami, C. and Ascaso, B. and Bellagamba, F. and Benoist, C. and Cappi, A. and Díaz-Sánchez, A. and Durret, F. and Farrens, S. and Gonzalez, A. H. and Iovino, A. and Licitra, R. and Maturi, M. and Mei, S. and Merson, A. and Munari, E. and Pelló, R. and Ricci, M. and Rocci, P. F. and Roncarelli, M. and Sarron, F. and Amoura, Y. and Andreon, S. and Apostolakos, N. and Arnaud, M. and Bardelli, S. and Bartlett, J. and Baugh, C. M. and Borgani, S. and Brodwin, M. and Castander, F. and Castignani, G. and Cucciati, O. and De Lucia, G. and Dubath, P. and Fosalba, P. and Giocoli, C. and Hoekstra, H. and Mamon, G. A. and Melin, J. B. and Moscardini, L. and Paltani, S. and Radovich, M. and Sartoris, B. and Schultheis, M. and Sereno, M. and Weller, J. and Burigana, C. and Carvalho, C. S. and Corcione, L. and Kurki-Suonio, H. and Lilje, P. B. and Sirri, G. and Toledo-Moreo, R. and Zamorani, G. (2019) 'Euclid preparation : III. Galaxy cluster detection in the wide photometric survey, performance and algorithm selection.', Astronomy & astrophysics., 627 . A23.


Galaxy cluster counts in bins of mass and redshift have been shown to be a competitive probe to test cosmological models. This method requires an efficient blind detection of clusters from surveys with a well-known selection function and robust mass estimates, which is particularly challenging at high redshift. The Euclid wide survey will cover 15 000 deg2 of the sky, avoiding contamination by light from our Galaxy and our solar system in the optical and near-infrared bands, down to magnitude 24 in the H-band. The resulting data will make it possible to detect a large number of galaxy clusters spanning a wide-range of masses up to redshift ∼2 and possibly higher. This paper presents the final results of the Euclid Cluster Finder Challenge (CFC), fourth in a series of similar challenges. The objective of these challenges was to select the cluster detection algorithms that best meet the requirements of the Euclid mission. The final CFC included six independent detection algorithms, based on different techniques, such as photometric redshift tomography, optimal filtering, hierarchical approach, wavelet and friend-of-friends algorithms. These algorithms were blindly applied to a mock galaxy catalog with representative Euclid-like properties. The relative performance of the algorithms was assessed by matching the resulting detections to known clusters in the simulations down to masses of M200 ∼ 1013.25 M⊙. Several matching procedures were tested, thus making it possible to estimate the associated systematic effects on completeness to < 3%. All the tested algorithms are very competitive in terms of performance, with three of them reaching > 80% completeness for a mean purity of 80% down to masses of 1014 M⊙ and up to redshift z = 2. Based on these results, two algorithms were selected to be implemented in the Euclid pipeline, the Adaptive Matched Identifier of Clustered Objects (AMICO) code, based on matched filtering, and the PZWav code, based on an adaptive wavelet approach.

Item Type:Article
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Publisher statement:Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited
Date accepted:27 May 2019
Date deposited:08 January 2020
Date of first online publication:26 June 2019
Date first made open access:08 January 2020

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