Euclid preparation. Three-dimensional galaxy clustering in configuration space: Three-point correlation function estimation
This paper presents and validates two algorithms—a direct counting method and a spherical harmonic decomposition approach—along with a random split technique for efficiently estimating the three-point correlation function within the Euclid mission's data analysis pipeline, demonstrating that a complete three-point clustering analysis of the final survey is computationally feasible while meeting scientific requirements.
Original authors: Euclid Collaboration, A. Veropalumbo (INAF-Osservatorio Astronomico di Brera, Via Brera 28, 20122 Milano, Italy, INFN-Sezione di Genova, Via Dodecaneso 33, 16146, Genova, Italy, Dipartimento di Fisica, Università di Genova, Via Dodecaneso 33, 16146, Genova, Italy), M. Moresco (Dipartimento di Fisica e Astronomia "Augusto Righi" - Alma Mater Studiorum Università di Bologna, via Piero Gobetti 93/2, 40129 Bologna, Italy, INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), F. Marulli (Dipartimento di Fisica e Astronomia "Augusto Righi" - Alma Mater Studiorum Università di Bologna, via Piero Gobetti 93/2, 40129 Bologna, Italy, INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy, INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy), E. Branchini (Dipartimento di Fisica, Università di Genova, Via Dodecaneso 33, 16146, Genova, Italy, INFN-Sezione di Genova, Via Dodecaneso 33, 16146, Genova, Italy, INAF-Osservatorio Astronomico di Brera, Via Brera 28, 20122 Milano, Italy), M. Guidi (Dipartimento di Fisica e Astronomia, Università di Bologna, Via Gobetti 93/2, 40129 Bologna, Italy, INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), A. Farina (Dipartimento di Fisica, Università di Genova, Via Dodecaneso 33, 16146, Genova, Italy, INAF-Osservatorio Astronomico di Brera, Via Brera 28, 20122 Milano, Italy, INFN-Sezione di Genova, Via Dodecaneso 33, 16146, Genova, Italy), A. Pugno (Universität Bonn, Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany), E. Sefusatti (INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy, IFPU, Institute for Fundamental Physics of the Universe, via Beirut 2, 34151 Trieste, Italy, INFN, Sezione di Trieste, Via Valerio 2, 34127 Trieste TS, Italy), D. Tavagnacco (INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy), F. Rizzo (INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy), E. Romelli (INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy), S. de la Torre (Aix-Marseille Université, CNRS, CNES, LAM, Marseille, France), A. Eggemeier (Universität Bonn, Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany), E. Sihvola (Department of Physics and Helsinki Institute of Physics, Gustaf Hällströmin katu 2, University of Helsinki, 00014 Helsinki, Finland), M. Viel (IFPU, Institute for Fundamental Physics of the Universe, via Beirut 2, 34151 Trieste, Italy, INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy, SISSA, International School for Advanced Studies, Via Bonomea 265, 34136 Trieste TS, Italy, INFN, Sezione di Trieste, Via Valerio 2, 34127 Trieste TS, Italy, ICSC - Centro Nazionale di Ricerca in High Performance Computing, Big Data e Quantum Computing, Via Magnanelli 2, Bologna, Italy), N. Aghanim (Université Paris-Saclay, CNRS, Institut d'astrophysique spatiale, 91405, Orsay, France), B. Altieri (ESAC/ESA, Camino Bajo del Castillo, s/n., Urb. Villafranca del Castillo, 28692 Villanueva de la Cañada, Madrid, Spain), S. Andreon (INAF-Osservatorio Astronomico di Brera, Via Brera 28, 20122 Milano, Italy), N. Auricchio (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), C. Baccigalupi (IFPU, Institute for Fundamental Physics of the Universe, via Beirut 2, 34151 Trieste, Italy, INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy, INFN, Sezione di Trieste, Via Valerio 2, 34127 Trieste TS, Italy, SISSA, International School for Advanced Studies, Via Bonomea 265, 34136 Trieste TS, Italy), M. Baldi (Dipartimento di Fisica e Astronomia, Università di Bologna, Via Gobetti 93/2, 40129 Bologna, Italy, INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy, INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy), S. Bardelli (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), P. Battaglia (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), A. Biviano (INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy, IFPU, Institute for Fundamental Physics of the Universe, via Beirut 2, 34151 Trieste, Italy), M. Brescia (Department of Physics "E. Pancini", University Federico II, Via Cinthia 6, 80126, Napoli, Italy, INAF-Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy), S. Camera (Dipartimento di Fisica, Università degli Studi di Torino, Via P. Giuria 1, 10125 Torino, Italy, INFN-Sezione di Torino, Via P. Giuria 1, 10125 Torino, Italy, INAF-Osservatorio Astrofisico di Torino, Via Osservatorio 20, 10025 Pino Torinese), G. Cañas-Herrera (Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK, Leiden Observatory, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands), V. Capobianco (INAF-Osservatorio Astrofisico di Torino, Via Osservatorio 20, 10025 Pino Torinese), C. Carbone (INAF-IASF Milano, Via Alfonso Corti 12, 20133 Milano, Italy), V. F. Cardone (INAF-Osservatorio Astronomico di Roma, Via Frascati 33, 00078 Monteporzio Catone, Italy, INFN-Sezione di Roma, Piazzale Aldo Moro, 2 - c/o Dipartimento di Fisica, Edificio G. Marconi, 00185 Roma, Italy), J. Carretero (Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, Port d'Informació Científica, Campus UAB, C. Albareda s/n, 08193 Bellaterra), S. Casas (Institute for Theoretical Particle Physics and Cosmology, Deutsches Zentrum für Luft- und Raumfahrt e. V), M. Castellano (INAF-Osservatorio Astronomico di Roma, Via Frascati 33, 00078 Monteporzio Catone, Italy), G. Castignani (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), S. Cavuoti (INAF-Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy, INFN section of Naples, Via Cinthia 6, 80126, Napoli, Italy), K. C. Chambers (Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA), A. Cimatti (Dipartimento di Fisica e Astronomia "Augusto Righi" - Alma Mater Studiorum Università di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy), C. Colodro-Conde (Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife, Spain), G. Congedo (Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK), C. J. Conselice (Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK), L. Conversi (European Space Agency/ESRIN, Largo Galileo Galilei 1, 00044 Frascati, Roma, Italy, ESAC/ESA, Camino Bajo del Castillo, s/n., Urb. Villafranca del Castillo, 28692 Villanueva de la Cañada, Madrid, Spain), Y. Copin (Université Claude Bernard Lyon 1, CNRS/IN2P3, IP2I Lyon, UMR 5822, Villeurbanne, F-69100, France), F. Courbin (Institut de Ciències del Cosmos, Institució Catalana de Recerca i Estudis Avançats, Institut de Ciencies de l'Espai), H. M. Courtois (UCB Lyon 1, CNRS/IN2P3, IUF, IP2I Lyon, 4 rue Enrico Fermi, 69622 Villeurbanne, France), A. Da Silva (Departamento de Física, Faculdade de Ciências, Universidade de Lisboa, Edifício C8, Campo Grande, PT1749-016 Lisboa, Portugal, Instituto de Astrofísica e Ciências do Espaço, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal), H. Degaudenzi (Department of Astronomy, University of Geneva, ch. d'Ecogia 16, 1290 Versoix, Switzerland), G. De Lucia (INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy), H. Dole (Université Paris-Saclay, CNRS, Institut d'astrophysique spatiale, 91405, Orsay, France), F. Dubath (Department of Astronomy, University of Geneva, ch. d'Ecogia 16, 1290 Versoix, Switzerland), X. Dupac (ESAC/ESA, Camino Bajo del Castillo, s/n., Urb. Villafranca del Castillo, 28692 Villanueva de la Cañada, Madrid, Spain), S. Dusini (INFN-Padova, Via Marzolo 8, 35131 Padova, Italy), S. Escoffier (Aix-Marseille Université, CNRS/IN2P3, CPPM, Marseille, France), M. Farina (INAF-Istituto di Astrofisica e Planetologia Spaziali, via del Fosso del Cavaliere, 100, 00100 Roma, Italy), R. Farinelli (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), F. Faustini (INAF-Osservatorio Astronomico di Roma, Via Frascati 33, 00078 Monteporzio Catone, Italy, Space Science Data Center, Italian Space Agency, via del Politecnico snc, 00133 Roma, Italy), S. Ferriol (Université Claude Bernard Lyon 1, CNRS/IN2P3, IP2I Lyon, UMR 5822, Villeurbanne, F-69100, France), F. Finelli (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy, INFN-Bologna, Via Irnerio 46, 40126 Bologna, Italy), P. Fosalba (Institut d'Estudis Espacials de Catalunya, Institute of Space Sciences), S. Fotopoulou (School of Physics, HH Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol, BS8 1TL, UK), M. Frailis (INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy), E. Franceschi (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), M. Fumana (INAF-IASF Milano, Via Alfonso Corti 12, 20133 Milano, Italy), S. Galeotta (INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy), K. George (University Observatory, LMU Faculty of Physics, Scheinerstr. 1, 81679 Munich, Germany), W. Gillard (Aix-Marseille Université, CNRS/IN2P3, CPPM, Marseille, France), B. Gillis (Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK), C. Giocoli (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy, INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy), P. Gómez-Alvarez (FRACTAL S.L.N.E., calle Tulipán 2, Portal 13 1A, 28231, Las Rozas de Madrid, Spain, ESAC/ESA, Camino Bajo del Castillo, s/n., Urb. Villafranca del Castillo, 28692 Villanueva de la Cañada, Madrid, Spain), J. Gracia-Carpio (Max Planck Institute for Extraterrestrial Physics, Giessenbachstr. 1, 85748 Garching, Germany), A. Grazian (INAF-Osservatorio Astronomico di Padova, Via dell'Osservatorio 5, 35122 Padova, Italy), F. Grupp (Max Planck Institute for Extraterrestrial Physics, Giessenbachstr. 1, 85748 Garching, Germany, Universitäts-Sternwarte München, Fakultät für Physik, Ludwig-Maximilians-Universität München, Scheinerstr. 1, 81679 München, Germany), L. Guzzo (Dipartimento di Fisica "Aldo Pontremoli", Università degli Studi di Milano, Via Celoria 16, 20133 Milano, Italy, INAF-Osservatorio Astronomico di Brera, Via Brera 28, 20122 Milano, Italy, INFN-Sezione di Milano, Via Celoria 16, 20133 Milano, Italy), W. Holmes (Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA, 91109, USA), F. Hormuth (Felix Hormuth Engineering, Goethestr. 17, 69181 Leimen, Germany), A. Hornstrup (Technical University of Denmark, Elektrovej 327, 2800 Kgs. Lyngby, Denmark, Cosmic Dawn Center), K. Jahnke (Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany), M. Jhabvala (NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA), B. Joachimi (Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK), S. Kermiche (Aix-Marseille Université, CNRS/IN2P3, CPPM, Marseille, France), A. Kiessling (Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA, 91109, USA), B. Kubik (Université Claude Bernard Lyon 1, CNRS/IN2P3, IP2I Lyon, UMR 5822, Villeurbanne, F-69100, France), M. Kunz (Université de Genève, Département de Physique Théorique and Centre for Astroparticle Physics, 24 quai Ernest-Ansermet, CH-1211 Genève 4, Switzerland), H. Kurki-Suonio (Department of Physics, P.O. Box 64, University of Helsinki, 00014 Helsinki, Finland, Helsinki Institute of Physics, Gustaf Hällströmin katu 2, University of Helsinki, 00014 Helsinki, Finland), A. M. C. Le Brun (Laboratoire d'etude de l'Univers et des phenomenes eXtremes, Observatoire de Paris, Université PSL, Sorbonne Université, CNRS, 92190 Meudon, France), S. Ligori (INAF-Osservatorio Astrofisico di Torino, Via Osservatorio 20, 10025 Pino Torinese), P. B. Lilje (Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, 0315 Oslo, Norway), V. Lindholm (Department of Physics, P.O. Box 64, University of Helsinki, 00014 Helsinki, Finland, Helsinki Institute of Physics, Gustaf Hällströmin katu 2, University of Helsinki, 00014 Helsinki, Finland), I. Lloro (SKAO, Jodrell Bank, Lower Withington, Macclesfield SK11 9FT, UK), G. Mainetti (Centre de Calcul de l'IN2P3/CNRS, 21 avenue Pierre de Coubertin 69627 Villeurbanne Cedex, France), D. Maino (Dipartimento di Fisica "Aldo Pontremoli", Università degli Studi di Milano, Via Celoria 16, 20133 Milano, Italy, INAF-IASF Milano, Via Alfonso Corti 12, 20133 Milano, Italy, INFN-Sezione di Milano, Via Celoria 16, 20133 Milano, Italy), E. Maiorano (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), O. Mansutti (INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy), S. Marcin (University of Applied Sciences and Arts of Northwestern Switzerland, School of Computer Science, 5210 Windisch, Switzerland), O. Marggraf (Universität Bonn, Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany), M. Martinelli (INAF-Osservatorio Astronomico di Roma, Via Frascati 33, 00078 Monteporzio Catone, Italy, INFN-Sezione di Roma, Piazzale Aldo Moro, 2 - c/o Dipartimento di Fisica, Edificio G. Marconi, 00185 Roma, Italy), N. Martinet (Aix-Marseille Université, CNRS, CNES, LAM, Marseille, France), R. J. Massey (Department of Physics, Institute for Computational Cosmology, Durham University, South Road, Durham, DH1 3LE, UK), E. Medinaceli (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), S. Mei (Université Paris Cité, CNRS, Astroparticule et Cosmologie, 75013 Paris, France, CNRS-UCB International Research Laboratory, Centre Pierre Binétruy, IRL2007, CPB-IN2P3, Berkeley, USA), M. Melchior (University of Applied Sciences and Arts of Northwestern Switzerland, School of Engineering, 5210 Windisch, Switzerland), Y. Mellier (Institut d'Astrophysique de Paris, 98bis Boulevard Arago, 75014, Paris, France, Institut d'Astrophysique de Paris, UMR 7095, CNRS, and Sorbonne Université, 98 bis boulevard Arago, 75014 Paris, France), M. Meneghetti (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy, INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy), E. Merlin (INAF-Osservatorio Astronomico di Roma, Via Frascati 33, 00078 Monteporzio Catone, Italy), G. Meylan (Institute of Physics, Laboratory of Astrophysics, Ecole Polytechnique Fédérale de Lausanne), A. Mora (Telespazio UK S.L. for European Space Agency), L. Moscardini (Dipartimento di Fisica e Astronomia "Augusto Righi" - Alma Mater Studiorum Università di Bologna, via Piero Gobetti 93/2, 40129 Bologna, Italy, INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy, INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy), C. Neissner (Institut de Física d'Altes Energies, Port d'Informació Científica, Campus UAB, C. Albareda s/n, 08193 Bellaterra), S. -M. Niemi (European Space Agency/ESTEC, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands), J. W. Nightingale (School of Mathematics, Statistics and Physics, Newcastle University, Herschel Building, Newcastle-upon-Tyne, NE1 7RU, UK), C. Padilla (Institut de Física d'Altes Energies), S. Paltani (Department of Astronomy, University of Geneva, ch. d'Ecogia 16, 1290 Versoix, Switzerland), F. Pasian (INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy), K. Pedersen (DARK, Niels Bohr Institute, University of Copenhagen, Jagtvej 155, 2200 Copenhagen, Denmark), W. J. Percival (Waterloo Centre for Astrophysics, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada, Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada, Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5, Canada), V. Pettorino (European Space Agency/ESTEC, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands), S. Pires (Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, 91191, Gif-sur-Yvette, France), G. Polenta (Space Science Data Center, Italian Space Agency, via del Politecnico snc, 00133 Roma, Italy), M. Poncet (Centre National d'Etudes Spatiales -- Centre spatial de Toulouse, 18 avenue Edouard Belin, 31401 Toulouse Cedex 9, France), L. A. Popa (Institute of Space Science, Str. Atomistilor, nr. 409 Măgurele, Ilfov, 077125, Romania), L. Pozzetti (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), F. Raison (Max Planck Institute for Extraterrestrial Physics, Giessenbachstr. 1, 85748 Garching, Germany), A. Renzi (Dipartimento di Fisica e Astronomia "G. Galilei", Università di Padova, Via Marzolo 8, 35131 Padova, Italy, INFN-Padova, Via Marzolo 8, 35131 Padova, Italy, INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), J. Rhodes (Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA, 91109, USA), G. Riccio (INAF-Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy), M. Roncarelli (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), R. Saglia (Universitäts-Sternwarte München, Fakultät für Physik, Ludwig-Maximilians-Universität München, Scheinerstr. 1, 81679 München, Germany, Max Planck Institute for Extraterrestrial Physics, Giessenbachstr. 1, 85748 Garching, Germany), Z. Sakr (Institut für Theoretische Physik, University of Heidelberg, Philosophenweg 16, 69120 Heidelberg, Germany, Institut de Recherche en Astrophysique et Planétologie, Université St Joseph, Faculty of Sciences, Beirut, Lebanon), D. Sapone (Departamento de Física, FCFM, Universidad de Chile, Blanco Encalada 2008, Santiago, Chile), B. Sartoris (Universitäts-Sternwarte München, Fakultät für Physik, Ludwig-Maximilians-Universität München, Scheinerstr. 1, 81679 München, Germany, INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy), P. Schneider (Universität Bonn, Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany), T. Schrabback (Universität Innsbruck, Institut für Astro- und Teilchenphysik, Technikerstr. 25/8, 6020 Innsbruck, Austria), A. Secroun (Aix-Marseille Université, CNRS/IN2P3, CPPM, Marseille, France), G. Seidel (Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany), S. Serrano (Institut d'Estudis Espacials de Catalunya, Satlantis, University Science Park, Sede Bld 48940, Leioa-Bilbao, Spain, Institute of Space Sciences), P. Simon (Universität Bonn, Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany), C. Sirignano (Dipartimento di Fisica e Astronomia "G. Galilei", Università di Padova, Via Marzolo 8, 35131 Padova, Italy, INFN-Padova, Via Marzolo 8, 35131 Padova, Italy), G. Sirri (INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy), L. Stanco (INFN-Padova, Via Marzolo 8, 35131 Padova, Italy), J. Steinwagner (Max Planck Institute for Extraterrestrial Physics, Giessenbachstr. 1, 85748 Garching, Germany), P. Tallada-Crespí (Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, Port d'Informació Científica, Campus UAB, C. Albareda s/n, 08193 Bellaterra), A. N. Taylor (Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK), I. Tereno (Departamento de Física, Faculdade de Ciências, Universidade de Lisboa, Edifício C8, Campo Grande, PT1749-016 Lisboa, Portugal, Instituto de Astrofísica e Ciências do Espaço, Faculdade de Ciências, Universidade de Lisboa, Tapada da Ajuda, 1349-018 Lisboa, Portugal), N. Tessore (Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK), S. Toft (Cosmic Dawn Center, Niels Bohr Institute, University of Copenhagen, Jagtvej 128, 2200 Copenhagen, Denmark), R. Toledo-Moreo (Universidad Politécnica de Cartagena, Departamento de Electrónica y Tecnología de Computadoras, Plaza del Hospital 1, 30202 Cartagena, Spain), F. Torradeflot (Port d'Informació Científica, Campus UAB, C. Albareda s/n, 08193 Bellaterra, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas), I. Tutusaus (Institute of Space Sciences, Institut d'Estudis Espacials de Catalunya, Institut de Recherche en Astrophysique et Planétologie), L. Valenziano (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy, INFN-Bologna, Via Irnerio 46, 40126 Bologna, Italy), J. Valiviita (Department of Physics, P.O. Box 64, University of Helsinki, 00014 Helsinki, Finland, Helsinki Institute of Physics, Gustaf Hällströmin katu 2, University of Helsinki, 00014 Helsinki, Finland), T. Vassallo (INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy), G. Verdoes Kleijn (Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands), Y. Wang (Caltech/IPAC, 1200 E. California Blvd., Pasadena, CA 91125, USA), J. Weller (Universitäts-Sternwarte München, Fakultät für Physik, Ludwig-Maximilians-Universität München, Scheinerstr. 1, 81679 München, Germany, Max Planck Institute for Extraterrestrial Physics, Giessenbachstr. 1, 85748 Garching, Germany), G. Zamorani (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), F. M. Zerbi (INAF-Osservatorio Astronomico di Brera, Via Brera 28, 20122 Milano, Italy), E. Zucca (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), V. Allevato (INAF-Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy), M. Ballardini (Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Ferrara, Via Giuseppe Saragat 1, 44122 Ferrara, Italy, Istituto Nazionale di Fisica Nucleare, Sezione di Ferrara, Via Giuseppe Saragat 1, 44122 Ferrara, Italy, INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), C. Benoist (Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Bd de l'Observatoire, CS 34229, 06304 Nice cedex 4, France), M. Bolzonella (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), E. Bozzo (Department of Astronomy, University of Geneva, ch. d'Ecogia 16, 1290 Versoix, Switzerland), C. Burigana (INAF, Istituto di Radioastronomia, Via Piero Gobetti 101, 40129 Bologna, Italy, INFN-Bologna, Via Irnerio 46, 40126 Bologna, Italy), R. Cabanac (Institut de Recherche en Astrophysique et Planétologie), M. Calabrese (Astronomical Observatory of the Autonomous Region of the Aosta Valley, INAF-IASF Milano, Via Alfonso Corti 12, 20133 Milano, Italy), A. Cappi (Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Bd de l'Observatoire, CS 34229, 06304 Nice cedex 4, France, INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), T. Castro (INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy, INFN, Sezione di Trieste, Via Valerio 2, 34127 Trieste TS, Italy, IFPU, Institute for Fundamental Physics of the Universe, via Beirut 2, 34151 Trieste, Italy, ICSC - Centro Nazionale di Ricerca in High Performance Computing, Big Data e Quantum Computing, Via Magnanelli 2, Bologna, Italy), J. A. Escartin Vigo (Max Planck Institute for Extraterrestrial Physics, Giessenbachstr. 1, 85748 Garching, Germany), L. Gabarra (Department of Physics, Oxford University, Keble Road, Oxford OX1 3RH, UK), J. García-Bellido (Instituto de Física Teórica UAM-CSIC, Campus de Cantoblanco, 28049 Madrid, Spain), V. Gautard (CEA Saclay, DFR/IRFU, Service d'Astrophysique, Bat. 709, 91191 Gif-sur-Yvette, France), J. Macias-Perez (Univ. Grenoble Alpes, CNRS, Grenoble INP, LPSC-IN2P3, 53, Avenue des Martyrs, 38000, Grenoble, France), R. Maoli (Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 2, 00185 Roma, Italy, INAF-Osservatorio Astronomico di Roma, Via Frascati 33, 00078 Monteporzio Catone, Italy), J. Martín-Fleitas (Aurora Technology for European Space Agency), N. Mauri (Dipartimento di Fisica e Astronomia "Augusto Righi" - Alma Mater Studiorum Università di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy, INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy), R. B. Metcalf (Dipartimento di Fisica e Astronomia "Augusto Righi" - Alma Mater Studiorum Università di Bologna, via Piero Gobetti 93/2, 40129 Bologna, Italy, INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), P. Monaco (Dipartimento di Fisica - Sezione di Astronomia, Università di Trieste, Via Tiepolo 11, 34131 Trieste, Italy, INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy, INFN, Sezione di Trieste, Via Valerio 2, 34127 Trieste TS, Italy, IFPU, Institute for Fundamental Physics of the Universe, via Beirut 2, 34151 Trieste, Italy), A. Pezzotta (INAF-Osservatorio Astronomico di Brera, Via Brera 28, 20122 Milano, Italy), M. Pöntinen (Department of Physics, P.O. Box 64, University of Helsinki, 00014 Helsinki, Finland), I. Risso (INAF-Osservatorio Astronomico di Brera, Via Brera 28, 20122 Milano, Italy, INFN-Sezione di Genova, Via Dodecaneso 33, 16146, Genova, Italy), V. Scottez (Institut d'Astrophysique de Paris, 98bis Boulevard Arago, 75014, Paris, France, ICL, Junia, Université Catholique de Lille, LITL, 59000 Lille, France), M. Sereno (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy, INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy), M. Tenti (INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy), M. Tucci (Department of Astronomy, University of Geneva, ch. d'Ecogia 16, 1290 Versoix, Switzerland), M. Wiesmann (Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, 0315 Oslo, Norway), Y. Akrami (Instituto de Física Teórica UAM-CSIC, Campus de Cantoblanco, 28049 Madrid, Spain, CERCA/ISO, Department of Physics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA), G. Alguero (Univ. Grenoble Alpes, CNRS, Grenoble INP, LPSC-IN2P3, 53, Avenue des Martyrs, 38000, Grenoble, France), I. T. Andika (University Observatory, LMU Faculty of Physics, Scheinerstr. 1, 81679 Munich, Germany), G. Angora (INAF-Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy, Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Ferrara, Via Giuseppe Saragat 1, 44122 Ferrara, Italy), S. Anselmi (INFN-Padova, Via Marzolo 8, 35131 Padova, Italy, Dipartimento di Fisica e Astronomia "G. Galilei", Università di Padova, Via Marzolo 8, 35131 Padova, Italy, Laboratoire Univers et Théorie, Observatoire de Paris, Université PSL, Université Paris Cité, CNRS, 92190 Meudon, France), M. Archidiacono (Dipartimento di Fisica "Aldo Pontremoli", Università degli Studi di Milano, Via Celoria 16, 20133 Milano, Italy, INFN-Sezione di Milano, Via Celoria 16, 20133 Milano, Italy), F. Atrio-Barandela (Departamento de Física Fundamental. Universidad de Salamanca. Plaza de la Merced s/n. 37008 Salamanca, Spain), E. Aubourg (Université Paris Cité, CNRS, Astroparticule et Cosmologie, 75013 Paris, France, IRFU, CEA, Université Paris-Saclay 91191 Gif-sur-Yvette Cedex, France), L. Bazzanini (Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Ferrara, Via Giuseppe Saragat 1, 44122 Ferrara, Italy, INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), J. Bel (Aix-Marseille Université, Université de Toulon, CNRS, CPT, Marseille, France), D. Bertacca (Dipartimento di Fisica e Astronomia "G. Galilei", Università di Padova, Via Marzolo 8, 35131 Padova, Italy, INAF-Osservatorio Astronomico di Padova, Via dell'Osservatorio 5, 35122 Padova, Italy, INFN-Padova, Via Marzolo 8, 35131 Padova, Italy), M. Bethermin (Université de Strasbourg, CNRS, Observatoire astronomique de Strasbourg, UMR 7550, 67000 Strasbourg, France), F. Beutler (Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK), A. Blanchard (Institut de Recherche en Astrophysique et Planétologie), L. Blot (Center for Data-Driven Discovery, Kavli IPMU, Laboratoire d'etude de l'Univers et des phenomenes eXtremes, Observatoire de Paris, Université PSL, Sorbonne Université, CNRS, 92190 Meudon, France), H. Böhringer (Max Planck Institute for Extraterrestrial Physics, Giessenbachstr. 1, 85748 Garching, Germany, University Observatory, LMU Faculty of Physics, Scheinerstr. 1, 81679 Munich, Germany, Max-Planck-Institut für Physik, Boltzmannstr. 8, 85748 Garching, Germany), M. Bonici (Waterloo Centre for Astrophysics, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada, INAF-IASF Milano, Via Alfonso Corti 12, 20133 Milano, Italy), S. Borgani (Dipartimento di Fisica - Sezione di Astronomia, Università di Trieste, Via Tiepolo 11, 34131 Trieste, Italy, IFPU, Institute for Fundamental Physics of the Universe, via Beirut 2, 34151 Trieste, Italy, INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy, INFN, Sezione di Trieste, Via Valerio 2, 34127 Trieste TS, Italy, ICSC - Centro Nazionale di Ricerca in High Performance Computing, Big Data e Quantum Computing, Via Magnanelli 2, Bologna, Italy), M. L. Brown (Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK), S. Bruton (California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125, USA), A. Calabro (INAF-Osservatorio Astronomico di Roma, Via Frascati 33, 00078 Monteporzio Catone, Italy), B. Camacho Quevedo (IFPU, Institute for Fundamental Physics of the Universe, via Beirut 2, 34151 Trieste, Italy, SISSA, International School for Advanced Studies, Via Bonomea 265, 34136 Trieste TS, Italy, INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy), F. Caro (INAF-Osservatorio Astronomico di Roma, Via Frascati 33, 00078 Monteporzio Catone, Italy), C. S. Carvalho (Instituto de Astrofísica e Ciências do Espaço, Faculdade de Ciências, Universidade de Lisboa, Tapada da Ajuda, 1349-018 Lisboa, Portugal), F. Cogato (Dipartimento di Fisica e Astronomia "Augusto Righi" - Alma Mater Studiorum Università di Bologna, via Piero Gobetti 93/2, 40129 Bologna, Italy, INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), S. Conseil (Université Claude Bernard Lyon 1, CNRS/IN2P3, IP2I Lyon, UMR 5822, Villeurbanne, F-69100, France), A. R. Cooray (Department of Physics \& Astronomy, University of California Irvine, Irvine CA 92697, USA), O. Cucciati (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), S. Davini (INFN-Sezione di Genova, Via Dodecaneso 33, 16146, Genova, Italy), G. Desprez (Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands), A. Díaz-Sánchez (Departamento Física Aplicada, Universidad Politécnica de Cartagena, Campus Muralla del Mar, 30202 Cartagena, Murcia, Spain), S. Di Domizio (Dipartimento di Fisica, Università di Genova, Via Dodecaneso 33, 16146, Genova, Italy, INFN-Sezione di Genova, Via Dodecaneso 33, 16146, Genova, Italy), J. M. Diego (Instituto de Física de Cantabria, Edificio Juan Jordá, Avenida de los Castros, 39005 Santander, Spain), V. Duret (Aix-Marseille Université, CNRS/IN2P3, CPPM, Marseille, France), M. Y. Elkhashab (INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy, INFN, Sezione di Trieste, Via Valerio 2, 34127 Trieste TS, Italy, Dipartimento di Fisica - Sezione di Astronomia, Università di Trieste, Via Tiepolo 11, 34131 Trieste, Italy, IFPU, Institute for Fundamental Physics of the Universe, via Beirut 2, 34151 Trieste, Italy), A. Enia (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), Y. Fang (Universitäts-Sternwarte München, Fakultät für Physik, Ludwig-Maximilians-Universität München, Scheinerstr. 1, 81679 München, Germany), A. G. Ferrari (INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy), A. Finoguenov (Department of Physics, P.O. Box 64, University of Helsinki, 00014 Helsinki, Finland), F. Fontanot (INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy, IFPU, Institute for Fundamental Physics of the Universe, via Beirut 2, 34151 Trieste, Italy), A. Franco (INFN, Sezione di Lecce, Via per Arnesano, CP-193, 73100, Lecce, Italy, Department of Mathematics and Physics E. De Giorgi, University of Salento, Via per Arnesano, CP-I93, 73100, Lecce, Italy, INAF-Sezione di Lecce, c/o Dipartimento Matematica e Fisica, Via per Arnesano, 73100, Lecce, Italy), K. Ganga (Université Paris Cité, CNRS, Astroparticule et Cosmologie, 75013 Paris, France), T. Gasparetto (INAF-Osservatorio Astronomico di Roma, Via Frascati 33, 00078 Monteporzio Catone, Italy), E. Gaztanaga (Institute of Space Sciences, Institut d'Estudis Espacials de Catalunya, Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth PO1 3FX, UK), F. Giacomini (INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy), F. Gianotti (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), G. Gozaliasl (Department of Computer Science, Aalto University, PO Box 15400, Espoo, FI-00 076, Finland, Department of Physics, P.O. Box 64, University of Helsinki, 00014 Helsinki, Finland), A. Gruppuso (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy, INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy), C. M. Gutierrez (Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife, Spain, Universidad de La Laguna, Dpto. Astrofí sica, E-38206 La Laguna, Tenerife, Spain), A. Hall (Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK), H. Hildebrandt (Ruhr University Bochum, Faculty of Physics and Astronomy, Astronomical Institute), J. Hjorth (DARK, Niels Bohr Institute, University of Copenhagen, Jagtvej 155, 2200 Copenhagen, Denmark), S. Joudaki (Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth PO1 3FX, UK), J. J. E. Kajava (Department of Physics and Astronomy, Vesilinnantie 5, University of Turku, 20014 Turku, Finland, Finnish Centre for Astronomy with ESO, Serco for European Space Agency), Y. Kang (Department of Astronomy, University of Geneva, ch. d'Ecogia 16, 1290 Versoix, Switzerland), V. Kansal (ARC Centre of Excellence for Dark Matter Particle Physics, Melbourne, Australia, Centre for Astrophysics \& Supercomputing, Swinburne University of Technology, Hawthorn, Victoria 3122, Australia), D. Karagiannis (Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Ferrara, Via Giuseppe Saragat 1, 44122 Ferrara, Italy, Department of Physics and Astronomy, University of the Western Cape, Bellville, Cape Town, 7535, South Africa), K. Kiiveri (Department of Physics and Helsinki Institute of Physics, Gustaf Hällströmin katu 2, University of Helsinki, 00014 Helsinki, Finland), J. Kim (Department of Physics, Oxford University, Keble Road, Oxford OX1 3RH, UK), C. C. Kirkpatrick (Department of Physics and Helsinki Institute of Physics, Gustaf Hällströmin katu 2, University of Helsinki, 00014 Helsinki, Finland), S. Kruk (ESAC/ESA, Camino Bajo del Castillo, s/n., Urb. Villafranca del Castillo, 28692 Villanueva de la Cañada, Madrid, Spain), M. Lattanzi (Istituto Nazionale di Fisica Nucleare, Sezione di Ferrara, Via Giuseppe Saragat 1, 44122 Ferrara, Italy), L. Legrand (DAMTP, Centre for Mathematical Sciences, Wilberforce Road, Cambridge CB3 0WA, UK, Kavli Institute for Cosmology Cambridge, Madingley Road, Cambridge, CB3 0HA, UK), M. Lembo (Institut d'Astrophysique de Paris, UMR 7095, CNRS, and Sorbonne Université, 98 bis boulevard Arago, 75014 Paris, France), F. Lepori (Department of Astrophysics, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland), G. Leroy (Department of Physics, Centre for Extragalactic Astronomy, Durham University, South Road, Durham, DH1 3LE, UK, Department of Physics, Institute for Computational Cosmology, Durham University, South Road, Durham, DH1 3LE, UK), G. F. Lesci (Dipartimento di Fisica e Astronomia "Augusto Righi" - Alma Mater Studiorum Università di Bologna, via Piero Gobetti 93/2, 40129 Bologna, Italy, INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), J. Lesgourgues (Institute for Theoretical Particle Physics and Cosmology), T. I. Liaudat (IRFU, CEA, Université Paris-Saclay 91191 Gif-sur-Yvette Cedex, France), S. J. Liu (INAF-Istituto di Astrofisica e Planetologia Spaziali, via del Fosso del Cavaliere, 100, 00100 Roma, Italy), A. Loureiro (Oskar Klein Centre for Cosmoparticle Physics, Department of Physics, Stockholm University, Stockholm, SE-106 91, Sweden, Astrophysics Group, Blackett Laboratory, Imperial College London, London SW7 2AZ, UK), M. Magliocchetti (INAF-Istituto di Astrofisica e Planetologia Spaziali, via del Fosso del Cavaliere, 100, 00100 Roma, Italy), F. Mannucci (INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125, Firenze, Italy), C. J. A. P. Martins (Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal, Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, PT4150-762 Porto, Portugal), L. Maurin (Université Paris-Saclay, CNRS, Institut d'astrophysique spatiale, 91405, Orsay, France), M. Migliaccio (Dipartimento di Fisica, Università di Roma Tor Vergata, Via della Ricerca Scientifica 1, Roma, Italy, INFN, Sezione di Roma 2, Via della Ricerca Scientifica 1, Roma, Italy), M. Miluzio (ESAC/ESA, Camino Bajo del Castillo, s/n., Urb. Villafranca del Castillo, 28692 Villanueva de la Cañada, Madrid, Spain, HE Space for European Space Agency), C. Moretti (INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy, IFPU, Institute for Fundamental Physics of the Universe, via Beirut 2, 34151 Trieste, Italy, INFN, Sezione di Trieste, Via Valerio 2, 34127 Trieste TS, Italy), G. Morgante (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), S. Nadathur (Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth PO1 3FX, UK), K. Naidoo (Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth PO1 3FX, UK, Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany), P. Natoli (Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Ferrara, Via Giuseppe Saragat 1, 44122 Ferrara, Italy, Istituto Nazionale di Fisica Nucleare, Sezione di Ferrara, Via Giuseppe Saragat 1, 44122 Ferrara, Italy), A. Navarro-Alsina (Universität Bonn, Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany), S. Nesseris (Instituto de Física Teórica UAM-CSIC, Campus de Cantoblanco, 28049 Madrid, Spain), L. Pagano (Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Ferrara, Via Giuseppe Saragat 1, 44122 Ferrara, Italy, Istituto Nazionale di Fisica Nucleare, Sezione di Ferrara, Via Giuseppe Saragat 1, 44122 Ferrara, Italy), D. Paoletti (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy, INFN-Bologna, Via Irnerio 46, 40126 Bologna, Italy), F. Passalacqua (Dipartimento di Fisica e Astronomia "G. Galilei", Università di Padova, Via Marzolo 8, 35131 Padova, Italy, INFN-Padova, Via Marzolo 8, 35131 Padova, Italy), K. Paterson (Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany), L. Patrizii (INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy), R. Paviot (Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, 91191, Gif-sur-Yvette, France), A. Pisani (Aix-Marseille Université, CNRS/IN2P3, CPPM, Marseille, France), D. Potter (Department of Astrophysics, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland), G. W. Pratt (Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, 91191, Gif-sur-Yvette, France), S. Quai (Dipartimento di Fisica e Astronomia "Augusto Righi" - Alma Mater Studiorum Università di Bologna, via Piero Gobetti 93/2, 40129 Bologna, Italy, INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), M. Radovich (INAF-Osservatorio Astronomico di Padova, Via dell'Osservatorio 5, 35122 Padova, Italy), K. Rojas (University of Applied Sciences and Arts of Northwestern Switzerland, School of Computer Science, 5210 Windisch, Switzerland), W. Roster (Max Planck Institute for Extraterrestrial Physics, Giessenbachstr. 1, 85748 Garching, Germany), S. Sacquegna (INAF - Osservatorio Astronomico d'Abruzzo, Via Maggini, 64100, Teramo, Italy), M. Sahlén (Theoretical astrophysics, Department of Physics and Astronomy, Uppsala University, Box 516, 751 37 Uppsala, Sweden), D. B. Sanders (Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA), E. Sarpa (SISSA, International School for Advanced Studies, Via Bonomea 265, 34136 Trieste TS, Italy, ICSC - Centro Nazionale di Ricerca in High Performance Computing, Big Data e Quantum Computing, Via Magnanelli 2, Bologna, Italy, INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy), A. Schneider (Department of Astrophysics, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland), D. Sciotti (INAF-Osservatorio Astronomico di Roma, Via Frascati 33, 00078 Monteporzio Catone, Italy, INFN-Sezione di Roma, Piazzale Aldo Moro, 2 - c/o Dipartimento di Fisica, Edificio G. Marconi, 00185 Roma, Italy), E. Sellentin (Mathematical Institute, University of Leiden, Einsteinweg 55, 2333 CA Leiden, The Netherlands, Leiden Observatory, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands), L. C. Smith (Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK), J. G. Sorce (Univ. Lille, CNRS, Centrale Lille, UMR 9189 CRIStAL, 59000 Lille, France, Université Paris-Saclay, CNRS, Institut d'astrophysique spatiale, 91405, Orsay, France), K. Tanidis (Department of Physics, Oxford University, Keble Road, Oxford OX1 3RH, UK), C. Tao (Aix-Marseille Université, CNRS/IN2P3, CPPM, Marseille, France), F. Tarsitano (Institute for Particle Physics and Astrophysics, Dept. of Physics, ETH Zurich, Wolfgang-Pauli-Strasse 27, 8093 Zurich, Switzerland, Department of Astronomy, University of Geneva, ch. d'Ecogia 16, 1290 Versoix, Switzerland), G. Testera (INFN-Sezione di Genova, Via Dodecaneso 33, 16146, Genova, Italy), R. Teyssier (Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544, USA), S. Tosi (Dipartimento di Fisica, Università di Genova, Via Dodecaneso 33, 16146, Genova, Italy, INFN-Sezione di Genova, Via Dodecaneso 33, 16146, Genova, Italy, INAF-Osservatorio Astronomico di Brera, Via Brera 28, 20122 Milano, Italy), A. Troja (Dipartimento di Fisica e Astronomia "G. Galilei", Università di Padova, Via Marzolo 8, 35131 Padova, Italy, INFN-Padova, Via Marzolo 8, 35131 Padova, Italy), A. Venhola (Space physics and astronomy research unit, University of Oulu, Pentti Kaiteran katu 1, FI-90014 Oulu, Finland), D. Vergani (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), F. Vernizzi (Institut de Physique Théorique, CEA, CNRS, Université Paris-Saclay 91191 Gif-sur-Yvette Cedex, France), G. Verza (International Centre for Theoretical Physics, Center for Computational Astrophysics, Flatiron Institute, 162 5th Avenue, 10010, New York, NY, USA), P. Vielzeuf (Aix-Marseille Université, CNRS/IN2P3, CPPM, Marseille, France), S. Vinciguerra (Aix-Marseille Université, CNRS, CNES, LAM, Marseille, France), N. A. Walton (Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK), A. H. Wright (Ruhr University Bochum, Faculty of Physics and Astronomy, Astronomical Institute)
Original paper licensed under CC BY 4.0 (http://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Imagine the universe as a giant, three-dimensional party. In this party, galaxies are the guests. For a long time, astronomers have been studying this party by looking at how guests pair up (two-point statistics). They ask: "If I stand here, how likely am I to see another guest standing next to me?" This has been very successful, but it's like trying to understand a complex conversation by only listening to people whispering in pairs.
This paper is about upgrading the listening equipment to hear the whole group conversation. Specifically, it focuses on how three galaxies form a triangle. This is called the Three-Point Correlation Function (3PCF).
Here is a simple breakdown of what the authors did, using everyday analogies:
1. The Problem: Counting Triangles is Hard
To understand the shape of the universe, the team needs to count every possible triangle formed by three galaxies in a massive dataset (the Euclid survey, which will map millions of galaxies).
- The Challenge: If you have 1 million guests, counting every possible trio of guests is a mathematically impossible task for a standard computer. It's like trying to count every possible group of three people in a stadium of 100,000 fans by hand. The time it takes grows so fast (cubically) that it would take years or centuries to finish.
2. The Solution: Two Different Counting Strategies
The team developed a software pipeline (a set of instructions for computers) with two different ways to solve this counting problem:
Method A: The "Brute Force" Count (Direct Counting)
- How it works: It checks every single galaxy, finds its neighbors, and then checks every possible combination of three.
- The Analogy: This is like a detective who walks up to every person in the room and asks, "Who are your two best friends?" and writes it down. It is 100% accurate and exact, but it is incredibly slow.
- Verdict: The paper says this method is too slow for the final, massive Euclid survey. It's kept only as a "gold standard" to check if the other method is working correctly.
Method B: The "Harmonic" Shortcut (Spherical Harmonic Decomposition)
- How it works: Instead of counting every specific triangle, this method breaks the pattern of galaxies down into "waves" or "layers" (like breaking a complex sound into musical notes). It counts the patterns in these layers and then rebuilds the triangle count from them.
- The Analogy: Instead of counting every specific trio of people, you look at the general "vibe" of the crowd. You notice that people tend to cluster in certain shapes. You can reconstruct the number of triangles by analyzing these shapes.
- Verdict: This is much, much faster (scales quadratically instead of cubically). The paper proves that even though it's an approximation (it doesn't catch every tiny detail), it is accurate enough for the mission's scientific goals.
3. The "Split" Trick: Cutting the Workload
Even with the faster "Harmonic" method, counting the random background noise (used to calibrate the data) was still too heavy.
- The Innovation: The team introduced a "Random Split" technique.
- The Analogy: Imagine you need to count the number of leaves on 50,000 trees to calibrate your leaf-counting machine. Instead of climbing all 50,000 trees at once, you split the job. You send 25 different teams, each climbing 2,000 trees, and then you average their results.
- The Result: This trick reduced the computing time by a factor of 10 without losing accuracy. It's like getting a supercomputer to do the work of a mainframe.
4. The "Triangle Shape" Issue
The authors found that the "Harmonic" shortcut works perfectly for most triangle shapes (like a long, skinny triangle). However, it struggles a bit with isosceles triangles (where two sides are exactly the same length).
- The Analogy: Think of the shortcut as a translator who is great at translating long, flowing sentences but sometimes stumbles on very short, repetitive phrases.
- The Fix: The paper notes that for these specific "stumbling" shapes, the team can still use the slow "Brute Force" method because they are rare. For the vast majority of triangles, the fast method is perfect.
5. The Final Test: Did it Work?
The team ran thousands of tests using fake galaxy data (simulations) where they knew the answer in advance.
- The "Null Test": They created a fake universe where galaxies were placed randomly (like static on a TV screen). In this universe, there should be zero triangles. Their code correctly found zero triangles, proving it doesn't invent fake patterns.
- The Speed Test: They calculated how long it would take to process the final Euclid data.
- Old Way (Brute Force): Would take years.
- New Way (Harmonic + Split): Can be done in about one day.
Conclusion
This paper is essentially a "user manual" and "quality control report" for a new, super-fast calculator designed for the Euclid space telescope. It proves that we can now measure the complex 3D shapes of the universe (triangles of galaxies) quickly and accurately. This allows astronomers to break through current limits in understanding dark energy and the evolution of the cosmos, all without waiting centuries for a computer to finish the math.
Technical Summary: Three-dimensional galaxy clustering in configuration space: Three-point correlation function estimation
Problem Statement
The Euclid mission aims to map the large-scale structure of the Universe using a spectroscopic survey covering 50 Gpc³ with millions of galaxies. While two-point statistics (2PCF) are standard, the non-Gaussian nature of the late-time cosmic density field necessitates higher-order statistics, specifically the three-point correlation function (3PCF), to break parameter degeneracies and constrain cosmological models. However, estimating the 3PCF is computationally prohibitive for datasets of Euclid's scale. A direct triplet counting approach scales as O(N3), rendering it infeasible for the expected number of objects (N∼107) and the required random catalogues (typically 50 times denser than the data). Furthermore, the Euclid Science Ground Segment (ESGS) requires estimators that are not only accurate but also robust against survey geometry and selection effects, while adhering to strict computational constraints.
Methodology
The paper details the implementation and validation of the 3PCF-GC processing function within the Euclid ESGS pipeline. The code, written in C++ and integrated into the Euclid Development Environment (EDEN), employs two primary algorithms for triplet counting:
- Direct Counting (DC): A brute-force method that counts all auto- and cross-triplets in configuration space. While exact and suitable for benchmarking or rare objects (e.g., galaxy clusters), its O(N3) scaling makes it impractical for the full Euclid survey.
- Spherical Harmonic Decomposition (SHD): Based on the method by Slepian & Eisenstein (2015), this approach expands the local density field around each primary galaxy into spherical harmonics. By compressing the information into Legendre coefficients up to a maximum multipole order ℓmax, the algorithm reduces the complexity to O(N2). The 3PCF is then reconstructed either by summing the multipoles (Direct Sum, ζ^DS) or by directly estimating the Legendre coefficients of the 3PCF using a modified Szapudi–Szalay estimator (ζ^SE) that accounts for edge effects via a mode-mixing matrix.
To address the computational bottleneck of generating random triplets (required for the Szapudi–Szalay estimator), the authors implement a Random Split technique. The random catalogue is divided into Nsplit subsamples, and the 3PCF is estimated by averaging the results from these subsamples. This reduces the computational cost significantly without introducing significant systematic errors, provided the split factor is optimized.
The estimators utilize the Szapudi–Szalay formalism to isolate the connected 3PCF (ζ) from the disconnected parts (random and correlated pairs). The pipeline supports multiple triangle parametrizations (SIDE, THETA, COSTHETA) and outputs both the full 3PCF and the reduced 3PCF (Q).
Key Contributions
- Implementation: The development of a production-ready, parallelized (OpenMP) C++ code integrated into the Euclid ESGS pipeline, capable of handling the full spectroscopic survey data.
- Algorithmic Efficiency: The adoption of SHD as the reference method, demonstrating that it can process Euclid-scale datasets within feasible timeframes (days rather than years) while maintaining scientific accuracy.
- Random Split Optimization: The validation and implementation of the random split technique, which reduces the computational cost of random triplet counting by a factor of ∼10 for SHD and ∼500 for DC, with an optimal split factor of Nsplit=25 (corresponding to a random density 1.5–2 times the data density).
- Validation Framework: A comprehensive suite of tests including null tests on Gaussian mocks, convergence studies of the SHD expansion, and comparisons between the two edge-correction methods (ζ^DS vs. ζ^SE).
Results
- Convergence: The SHD method converges rapidly for non-isosceles triangle configurations. For ℓmax=10, the difference between SHD and the exact DC method is well within the expected statistical error (systematic bias < 10% of statistical uncertainty). However, convergence is slower for isosceles configurations (where r12≈r13), particularly at small scales where the 3PCF exhibits steep variations.
- Null Tests: Using 600 Gaussian mocks (which have zero intrinsic 3PCF), the pipeline recovered a null signal with systematic errors well below the 10% requirement, confirming the absence of significant biases in the estimator.
- Edge Corrections: Comparisons between the Direct Sum and the Slepian–Eisenstein estimator showed differences of less than 3% of the statistical error, indicating that edge effects are well-managed for the Euclid survey geometry.
- Computational Forecast: For the full Euclid spectroscopic survey (Data Release 1–3), the SHD method with Nsplit=25 and 32 threads is predicted to complete the 3PCF measurement for all configurations in approximately one day. In contrast, the DC method would require months to years, rendering it unfeasible for the full survey.
Significance
The paper establishes that a complete, high-precision three-point correlation function analysis of the final Euclid survey is computationally feasible. By validating the SHD method and the random split technique, the authors provide a robust toolkit for extracting non-Gaussian information from the Euclid data. The work confirms that while SHD is an approximation, it satisfies the mission's scientific requirements for systematic bias, allowing for the efficient measurement of cosmological parameters. The code is designed to be extensible, supporting future analyses of anisotropic 3PCF and higher-order N-point correlation functions, thereby ensuring the Euclid mission can fully exploit the statistical power of its vast galaxy catalogues.
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