Euclid: Quick Data Release (Q1) -- Secondary nuclei in early-type galaxies
Open Research Online (The Open University)
Abstract
Massive early-type galaxies (ETGs) are believed to form primarily through mergers of less massive progenitors, leaving behind numerous traces of violent formation histories, such as stellar streams and shells. A particularly striking signature of these mergers is the formation of supermassive black hole (SMBH) binaries, which can create depleted stellar cores through interactions with stars on radial orbits - a process known as core scouring. The secondary SMBH in such systems may still carry a dense stellar envelope and thereby remain observable for some time as a secondary nucleus, while it is sinking towards the shared gravitational potential of the merged galaxy. We leverage Euclid's Q1 Early Release data to systematically search for secondary nuclei in ETGs. We present a preliminary sample of 666 candidate systems distributed over 504 hosts (some of which contain multiple secondary nuclei). The vast majority of these fall at separations of 3 kpc to 15 kpc, indicative of normal mergers. 44 fall at projected separations of less than 2 kpc. We argue those candidates at very close angular separations are unlikely to be a consequence of chance alignments. We show that their stellar masses are mostly too large for them to be globular clusters and that a significant subset are unresolved even at Euclid's spatial resolution, rendering them too small to be dwarf galaxies. These may represent the highest-density nuclei of a previously merged galaxy, currently sinking into the centre of the new, common gravitational potential and thus likely to host a secondary SMBH. We then demonstrate that convolutional neural networks offer a viable avenue to detect multiple nuclei in the thirty-times larger sky coverage of the future Euclid DR1. Finally, we argue that our method could detect the remnants of a recoil event from two merged SMBHs.
Authors 71
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Max Planck Institute for Extraterrestrial Physics · Ludwig-Maximilians-Universität München
Affiliation as printed
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
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Max Planck Institute for Extraterrestrial Physics · Ludwig-Maximilians-Universität München
Affiliation as printed
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
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Max Planck Institute for Extraterrestrial Physics · Ludwig-Maximilians-Universität München
Affiliation as printed
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
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Institute for Space Astrophysics and Planetology · National Institute for Astrophysics
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INAF-Istituto di Astrofisica e Planetologia Spaziali, via del Fosso del Cavaliere, 100, 00100 Roma, Italy
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Centre National de la Recherche Scientifique · Université de Lille · Université Paris-Saclay · Institut d'Astrophysique Spatiale · Centre de Recherche en Informatique, Signal et Automatique de Lille · Centrale Lille Institut
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Univ. Lille, CNRS, Centrale Lille, UMR 9189 CRIStAL, 59000 Lille, France
Université Paris-Saclay, CNRS, Institut d'astrophysique spatiale, 91405, Orsay, France
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Centre National de la Recherche Scientifique · Observatoire astronomique de Strasbourg · Université de Strasbourg
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Université de Strasbourg, CNRS, Observatoire astronomique de Strasbourg, UMR 7550, 67000 Strasbourg, France
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European Space Astronomy Centre
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ESAC/ESA, Camino Bajo del Castillo, s/n., Urb. Villafranca del Castillo, 28692 Villanueva de la Cañada, Madrid, Spain
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Affiliation as printed
School of Mathematics and Physics, University of Surrey, Guildford, Surrey, GU2 7XH, UK
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Brera Astronomical Observatory
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INAF-Osservatorio Astronomico di Brera, Via Brera 28, 20122 Milano, Italy
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Osservatorio di Astrofisica e Scienza dello Spazio · National Institute for Astrophysics
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INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy
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Scuola Internazionale Superiore di Studi Avanzati · Trieste Astronomical Observatory · Istituto Nazionale di Fisica Nucleare, Sezione di Trieste · Institute for Fundamental Physics of the Universe
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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
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Osservatorio di Astrofisica e Scienza dello Spazio · National Institute for Astrophysics
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INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy
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Trieste Astronomical Observatory · Institute for Fundamental Physics of the Universe
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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
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Astronomical Observatory of Capodimonte · University of Naples Federico II
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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
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Istituto Nazionale di Fisica Nucleare, Sezione di Torino · Osservatorio Astrofisico di Torino · University of Turin · National Institute for Astrophysics
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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
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Osservatorio Astrofisico di Torino · National Institute for Astrophysics
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INAF-Osservatorio Astrofisico di Torino, Via Osservatorio 20, 10025 Pino Torinese
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National Institute for Astrophysics
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Port d'Informació Científica · Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas
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Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas
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Astronomical Observatory of Rome · National Institute for Astrophysics
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Osservatorio di Astrofisica e Scienza dello Spazio · National Institute for Astrophysics
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INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy
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Dipartimento di Fisica e Astronomia "Augusto Righi" - Alma Mater Studiorum Università di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy
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Instituto de Astrofísica de Canarias
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Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife, Spain
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Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
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European Space Agency · European Space Astronomy Centre · European Space Research Institute
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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
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Lyon 1 Université · Centre National de la Recherche Scientifique · Institut National de Physique Nucléaire et de Physique des Particules · Institut de Physique des 2 Infinis de Lyon
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Université Claude Bernard Lyon 1, CNRS/IN2P3, IP2I Lyon, UMR 5822, Villeurbanne, F-69100, France
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Institució Catalana de Recerca i Estudis Avançats · Institut de Ciències del Cosmos
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Institut de Ciències del Cosmos
Institució Catalana de Recerca i Estudis Avançats
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UCB Lyon 1, CNRS/IN2P3, IUF, IP2I Lyon, 4 rue Enrico Fermi, 69622 Villeurbanne, France
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Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK
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Department of Astronomy, University of Geneva, ch. d'Ecogia 16, 1290 Versoix, Switzerland
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Trieste Astronomical Observatory
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Centre National de la Recherche Scientifique · Université Paris-Saclay · Institut d'Astrophysique Spatiale
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Université Paris-Saclay, CNRS, Institut d'astrophysique spatiale, 91405, Orsay, France
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Department of Astronomy, University of Geneva, ch. d'Ecogia 16, 1290 Versoix, Switzerland
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Royal Observatory · University of Edinburgh
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Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
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European Space Astronomy Centre
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ESAC/ESA, Camino Bajo del Castillo, s/n., Urb. Villafranca del Castillo, 28692 Villanueva de la Cañada, Madrid, Spain
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Istituto Nazionale di Fisica Nucleare, Sezione di Padova
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INFN-Padova, Via Marzolo 8, 35131 Padova, Italy
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Centre National de la Recherche Scientifique · Aix-Marseille Université · Centre de physique des particules de Marseille · Institut National de Physique Nucléaire et de Physique des Particules
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Aix-Marseille Université, CNRS/IN2P3, CPPM, Marseille, France
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Institute for Space Astrophysics and Planetology · National Institute for Astrophysics
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INAF-Istituto di Astrofisica e Planetologia Spaziali, via del Fosso del Cavaliere, 100, 00100 Roma, Italy
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Lyon 1 Université · Centre National de la Recherche Scientifique · Institut National de Physique Nucléaire et de Physique des Particules · Institut de Physique des 2 Infinis de Lyon
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Université Claude Bernard Lyon 1, CNRS/IN2P3, IP2I Lyon, UMR 5822, Villeurbanne, F-69100, France
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Istituto Nazionale di Fisica Nucleare, Sezione di Bologna · Osservatorio di Astrofisica e Scienza dello Spazio · National Institute for Astrophysics
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INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy
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Trieste Astronomical Observatory
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INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy
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Osservatorio di Astrofisica e Scienza dello Spazio · National Institute for Astrophysics
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INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy
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National Institute for Astrophysics
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Trieste Astronomical Observatory
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Royal Observatory · University of Edinburgh
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Istituto Nazionale di Fisica Nucleare, Sezione di Bologna · Osservatorio di Astrofisica e Scienza dello Spazio · National Institute for Astrophysics
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Max Planck Institute for Extraterrestrial Physics · Ludwig-Maximilians-Universität München
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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
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Leiden University · Leiden Observatory
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Leiden Observatory, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
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Department of Physics, Lancaster University, Lancaster, LA1 4YB, UK
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Max Planck Institute for Astronomy
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Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
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Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
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University of Helsinki · Helsinki Institute of Physics
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Department of Physics and Helsinki Institute of Physics, Gustaf Hällströmin katu 2, University of Helsinki, 00014 Helsinki, Finland
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Centre National de la Recherche Scientifique · Aix-Marseille Université · Centre de physique des particules de Marseille · Institut National de Physique Nucléaire et de Physique des Particules
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Aix-Marseille Université, CNRS/IN2P3, CPPM, Marseille, France
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Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA, 91109, USA
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Lyon 1 Université · Centre National de la Recherche Scientifique · Institut National de Physique Nucléaire et de Physique des Particules · Institut de Physique des 2 Infinis de Lyon
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Université Claude Bernard Lyon 1, CNRS/IN2P3, IP2I Lyon, UMR 5822, Villeurbanne, F-69100, France
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Leiden University · Leiden Observatory
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Leiden Observatory, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
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Ludwig-Maximilians-Universität München
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Université de Genève, Département de Physique Théorique and Centre for Astroparticle Physics, 24 quai Ernest-Ansermet, CH-1211 Genève 4, Switzerland
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University of Helsinki · Helsinki Institute of Physics
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Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Sorbonne Université · Laboratoire d'Étude de l'Univers et des Phénomènes Extrêmes
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Laboratoire d'etude de l'Univers et des phenomenes eXtremes, Observatoire de Paris, Université PSL, Sorbonne Université, CNRS, 92190 Meudon, France
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Osservatorio Astrofisico di Torino · National Institute for Astrophysics
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Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, 0315 Oslo, Norway
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Centre National de la Recherche Scientifique · Centre de Calcul de l’Institut National de Physique Nucléaire et de Physique des Particules
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University of Milan · Istituto Nazionale di Fisica Nucleare, Sezione di Milano · National Institute for Astrophysics
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Dipartimento di Fisica "Aldo Pontremoli", Università degli Studi di Milano, Via Celoria 16, 20133 Milano, Italy
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Osservatorio di Astrofisica e Scienza dello Spazio · National Institute for Astrophysics
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INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy
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Astronomical Observatory of Rome · Istituto Nazionale di Fisica Nucleare, Sezione di Roma I · National Institute for Astrophysics
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INFN-Sezione di Roma, Piazzale Aldo Moro, 2 - c/o Dipartimento di Fisica, Edificio G. Marconi, 00185 Roma, Italy
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Centre National de la Recherche Scientifique · Aix-Marseille Université
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Aix-Marseille Université, CNRS, CNES, LAM, Marseille, France
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Istituto Nazionale di Fisica Nucleare, Sezione di Bologna · Osservatorio di Astrofisica e Scienza dello Spazio · National Institute for Astrophysics · University of Bologna
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Dipartimento di Fisica e Astronomia "Augusto Righi" - Alma Mater Studiorum Università di Bologna, via Piero Gobetti 93/2, 40129 Bologna, Italy
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INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy
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Osservatorio di Astrofisica e Scienza dello Spazio · National Institute for Astrophysics
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INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy
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Centre National de la Recherche Scientifique · Université Paris Cité · Institut National de Physique Nucléaire et de Physique des Particules · Centre Pierre Binétruy · University of California, Berkeley
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Université Paris Cité, CNRS, Astroparticule et Cosmologie, 75013 Paris, France
CNRS-UCB International Research Laboratory, Centre Pierre Binétruy, IRL2007, CPB-IN2P3, Berkeley, USA
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Centre National de la Recherche Scientifique · Institut d'Astrophysique de Paris · Sorbonne Université
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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
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Istituto Nazionale di Fisica Nucleare, Sezione di Bologna · Osservatorio di Astrofisica e Scienza dello Spazio · National Institute for Astrophysics
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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
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