Euclid: Early Release Observations of diffuse stellar structures and globular clusters as probes of the mass assembly of galaxies in the Dorado group^⋆

¹ Université de Strasbourg, CNRS, Observatoire astronomique de Strasbourg, UMR 7550, 67000 Strasbourg, France
² Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
³ INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy
⁴ Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, 9000 Gent, Belgium
⁵ Institut universitaire de France (IUF), 1 rue Descartes, 75231 PARIS CEDEX 05, France
⁶ Laboratoire d’Astrophysique de Bordeaux, CNRS and Université de Bordeaux, Allée Geoffroy St. Hilaire, 33165 Pessac, France
⁷ INAF – Osservatorio Astronomico d’Abruzzo, Via Maggini, 64100 Teramo, Italy
⁸ INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy
⁹ Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, 91191 Gif-sur-Yvette, France
¹⁰ INAF-Osservatorio Astronomico di Roma, Via Frascati 33, 00078 Monteporzio Catone, Italy
¹¹ Observatorio Nacional, Rua General Jose Cristino, 77-Bairro Imperial de Sao Cristovao, Rio de Janeiro 20921-400, Brazil
¹² Max Planck Institute for Extraterrestrial Physics, Giessenbachstr. 1, 85748 Garching, Germany
¹³ Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
¹⁴ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
¹⁵ INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
¹⁶ Department of Astrophysics/IMAPP, Radboud University, PO Box 9010 6500 GL Nijmegen, The Netherlands
¹⁷ Leiden Observatory, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
¹⁸ Universität Innsbruck, Institut für Astro- und Teilchenphysik, Technikerstr. 25/8, 6020 Innsbruck, Austria
¹⁹ Institute of Physics, Laboratory of Astrophysics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Observatoire de Sauverny, 1290 Versoix, Switzerland
²⁰ Visiting Fellow, Clare Hall, University of Cambridge, Cambridge, UK
²¹ Kapteyn Astronomical Institute, University of Groningen, PO Box 800 9700 AV Groningen, The Netherlands
²² Space physics and astronomy research unit, University of Oulu, Pentti Kaiteran katu 1, FI-90014 Oulu, Finland
²³ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
²⁴ Department of Physics, Université de Montréal, 2900 Edouard Montpetit Blvd, Montréal, Québec H3T 1J4, Canada
²⁵ Ciela Institute – Montréal Institute for Astrophysical Data Analysis and Machine Learning, Montréal, Québec, Canada
²⁶ Mila – Québec Artificial Intelligence Institute, Montréal, Québec, Canada
²⁷ Universitäts-Sternwarte München, Fakultät für Physik, Ludwig-Maximilians-Universität München, Scheinerstrasse 1, 81679 München, Germany
²⁸ ESAC/ESA, Camino Bajo del Castillo, s/n., Urb. Villafranca del Castillo, 28692 Villanueva de la Cañada, Madrid, Spain
²⁹ INAF-Osservatorio Astronomico di Brera, Via Brera 28, 20122 Milano, Italy
³⁰ IFPU, Institute for Fundamental Physics of the Universe, via Beirut 2, 34151 Trieste, Italy
³¹ INFN, Sezione di Trieste, Via Valerio 2, 34127 Trieste, TS, Italy
³² SISSA, International School for Advanced Studies, Via Bonomea 265, 34136 Trieste, TS, Italy
³³ Dipartimento di Fisica e Astronomia, Università di Bologna, Via Gobetti 93/2, 40129 Bologna, Italy
³⁴ INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy
³⁵ INAF-Osservatorio Astronomico di Padova, Via dell’Osservatorio 5, 35122 Padova, Italy
³⁶ Centre National d’Etudes Spatiales – Centre spatial de Toulouse, 18 avenue Edouard Belin, 31401 Toulouse Cedex 9, France
³⁷ Dipartimento di Fisica, Università di Genova, Via Dodecaneso 33, 16146 Genova, Italy
³⁸ INFN-Sezione di Genova, Via Dodecaneso 33, 16146 Genova, Italy
³⁹ Department of Physics “E. Pancini”, University Federico II, Via Cinthia 6, 80126 Napoli, Italy
⁴⁰ INAF-Osservatorio Astronomico di Capodimonte, Via Moiariello 16 80131 Napoli, Italy
⁴¹ INFN section of Naples, Via Cinthia 6, 80126 Napoli, Italy
⁴² Dipartimento di Fisica, Università degli Studi di Torino, Via P. Giuria 1, 10125 Torino, Italy
⁴³ INFN-Sezione di Torino, Via P. Giuria 1, 10125 Torino, Italy
⁴⁴ INAF-Osservatorio Astrofisico di Torino, Via Osservatorio 20, 10025 Pino Torinese (TO), Italy
⁴⁵ INAF-IASF Milano, Via Alfonso Corti 12, 20133 Milano, Italy
⁴⁶ Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), Avenida Complutense 40, 28040 Madrid, Spain
⁴⁷ Port d’Informació Científica, Campus UAB, C. Albareda s/n, 08193 Bellaterra (Barcelona), Spain
⁴⁸ Institute for Theoretical Particle Physics and Cosmology (TTK), RWTH Aachen University, 52056 Aachen, Germany
⁴⁹ Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth PO1 3FX, UK
⁵⁰ Dipartimento di Fisica e Astronomia “Augusto Righi” – Alma Mater Studiorum Università di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy
⁵¹ Instituto de Astrofísica de Canarias, Calle Vía Láctea s/n, 38204 San Cristóbal de La Laguna, Tenerife, Spain
⁵² Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
⁵³ European Space Agency/ESRIN, Largo Galileo Galilei 1, 00044 Frascati, Roma, Italy
⁵⁴ Université Claude Bernard Lyon 1, CNRS/IN2P3, IP2I Lyon, UMR 5822, Villeurbanne F-69100, France
⁵⁵ Institut de Ciències del Cosmos (ICCUB), Universitat de Barcelona (IEEC-UB), Martí i Franquès 1, 08028 Barcelona, Spain
⁵⁶ Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig de Lluís Companys 23, 08010 Barcelona, Spain
⁵⁷ UCB Lyon 1, CNRS/IN2P3, IUF, IP2I Lyon, 4 rue Enrico Fermi, 69622 Villeurbanne, France
⁵⁸ Department of Astronomy, University of Geneva, ch. d’Ecogia 16, 1290 Versoix, Switzerland
⁵⁹ INFN-Padova, Via Marzolo 8, 35131 Padova, Italy
⁶⁰ INAF-Istituto di Astrofisica e Planetologia Spaziali, via del Fosso del Cavaliere, 100, 00100 Roma, Italy
⁶¹ Space Science Data Center, Italian Space Agency, via del Politecnico snc, 00133 Roma, Italy
⁶² FRACTAL S.L.N.E., calle Tulipán 2, Portal 13 1A, 28231 Las Rozas de Madrid, Spain
⁶³ Dipartimento di Fisica “Aldo Pontremoli”, Università degli Studi di Milano, Via Celoria 16, 20133 Milano, Italy
⁶⁴ Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern 0315 Oslo, Norway
⁶⁵ Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
⁶⁶ Felix Hormuth Engineering, Goethestr. 17, 69181 Leimen, Germany
⁶⁷ Technical University of Denmark, Elektrovej 327, 2800 Kgs. Lyngby, Denmark
⁶⁸ Cosmic Dawn Center (DAWN), Copenhagen, Denmark
⁶⁹ Institut d’Astrophysique de Paris, UMR 7095, CNRS, and Sorbonne Université, 98 bis boulevard Arago, 75014 Paris, France
⁷⁰ NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
⁷¹ Department of Physics and Helsinki Institute of Physics, Gustaf Hällströmin katu 2, 00014 University of Helsinki, Finland
⁷² Aix-Marseille Université, CNRS/IN2P3, CPPM, Marseille, France
⁷³ Université de Genève, Département de Physique Théorique and Centre for Astroparticle Physics, 24 quai Ernest-Ansermet, CH-1211 Genève 4, Switzerland
⁷⁴ Department of Physics, P.O. Box 64 00014 University of Helsinki, Finland
⁷⁵ Helsinki Institute of Physics, Gustaf Hällströmin katu 2, University of Helsinki, Helsinki, Finland
⁷⁶ Aix-Marseille Université, CNRS, CNES, LAM, Marseille, France
⁷⁷ NOVA optical infrared instrumentation group at ASTRON, Oude Hoogeveensedijk 4, 7991PD Dwingeloo, The Netherlands
⁷⁸ University of Applied Sciences and Arts of Northwestern Switzerland, School of Engineering, 5210 Windisch, Switzerland
⁷⁹ Universität Bonn, Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany
⁸⁰ INFN-Sezione di Roma, Piazzale Aldo Moro, 2 – c/o Dipartimento di Fisica, Edificio G. Marconi, 00185 Roma, Italy
⁸¹ Dipartimento di Fisica e Astronomia “Augusto Righi” – Alma Mater Studiorum Università di Bologna, via Piero Gobetti 93/2, 40129 Bologna, Italy
⁸² Department of Physics, Institute for Computational Cosmology, Durham University, South Road, Durham DH1 3LE, UK
⁸³ Université Paris Cité, CNRS, Astroparticule et Cosmologie, 75013 Paris, France
⁸⁴ CNRS-UCB International Research Laboratory, Centre Pierre Binetruy, IRL2007, CPB-IN2P3, Berkeley, USA
⁸⁵ Institut de Física d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology, Campus UAB, 08193 Bellaterra (Barcelona), Spain
⁸⁶ School of Mathematics and Physics, University of Surrey, Guildford, Surrey GU2 7XH, UK
⁸⁷ European Space Agency/ESTEC, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
⁸⁸ DARK, Niels Bohr Institute, University of Copenhagen, Jagtvej 155, 2200 Copenhagen, Denmark
⁸⁹ Waterloo Centre for Astrophysics, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
⁹⁰ Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
⁹¹ Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5, Canada
⁹² Institute of Space Science, Str. Atomistilor, nr. 409 Măgurele, Ilfov 077125, Romania
⁹³ Dipartimento di Fisica e Astronomia “G. Galilei”, Università di Padova, Via Marzolo 8, 35131 Padova, Italy
⁹⁴ Departamento de Física, FCFM, Universidad de Chile, Blanco Encalada 2008, Santiago, Chile
⁹⁵ Institut d’Estudis Espacials de Catalunya (IEEC), Edifici RDIT, Campus UPC, 08860 Castelldefels, Barcelona, Spain
⁹⁶ Satlantis, University Science Park, Sede Bld 48940, Leioa-Bilbao, Spain
⁹⁷ Institute of Space Sciences (ICE, CSIC), Campus UAB, Carrer de Can Magrans, s/n, 08193 Barcelona, Spain
⁹⁸ Departamento de Física, Faculdade de Ciências, Universidade de Lisboa, Edifício C8, Campo Grande, PT1749-016 Lisboa, Portugal
⁹⁹ Instituto de Astrofísica e Ciências do Espaço, Faculdade de Ciências, Universidade de Lisboa, Tapada da Ajuda, 1349-018 Lisboa, Portugal
¹⁰⁰ Universidad Politécnica de Cartagena, Departamento de Electrónica y Tecnología de Computadoras, Plaza del Hospital 1, 30202 Cartagena, Spain
¹⁰¹ Institut de Recherche en Astrophysique et Planétologie (IRAP), Université de Toulouse, CNRS, UPS, CNES, 14 Av. Edouard Belin, 31400 Toulouse, France
¹⁰² Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125, USA
¹⁰³ Centre for Information Technology, University of Groningen, P.O. Box 11044 9700 CA Groningen, The Netherlands
¹⁰⁴ INAF, Istituto di Radioastronomia, Via Piero Gobetti 101, 40129 Bologna, Italy
¹⁰⁵ INFN-Bologna, Via Irnerio 46, 40126 Bologna, Italy
¹⁰⁶ Aurora Technology for European Space Agency (ESA), Camino bajo del Castillo, s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
¹⁰⁷ Institut d’Astrophysique de Paris, 98bis Boulevard Arago, 75014 Paris, France
¹⁰⁸ ICL, Junia, Université Catholique de Lille, LITL, 59000 Lille, France

^⋆⋆ Corresponding author: m.urbano@unistra.fr

Received: 19 December 2024
Accepted: 23 June 2025

Abstract

Deep surveys have helped to unveil the history of past and present galaxy mergers, and, in particular, uncovering their tidal debris and co-located globular clusters (GCs). Euclid’s unique combination of capabilities (spatial resolution, depth, and wide sky coverage) will make it a groundbreaking tool for galactic archaeology in the Local Universe, bringing low-surface-brightness (LSB) science into the era of large-scale astronomical surveys. Euclid’s Early Release Observations (ERO) demonstrate this potential with a field of view that includes several galaxies in the Dorado group. In this paper, we aim to derive from this image a mass assembly scenario for its main galaxies: NGC 1549, NGC 1553, and NGC 1546. We detected their internal and external diffuse structures, and identified candidate GCs. By analysing the colours and distributions of the diffuse structures and candidate GCs, we can place constraints on the galaxies’ mass assembly and merger histories. The results demonstrate that feature morphology, surface brightness, colours, and GC density profiles are consistent with galaxies that have undergone different merger scenarios. We classify NGC 1549 as a pure elliptical galaxy that has undergone a major merger. NGC 1553 appears to have recently transitioned from a late-type galaxy to early type, after a series of radial minor to intermediate mergers. NGC 1546 is a rare specimen of galaxy with an undisturbed disk and a prominent diffuse stellar halo, which we infer has been fed by minor mergers and then disturbed by the tidal effect from NGC 1553. Finally, we identify limitations specific to the observing conditions of this ERO, in particular, stray light in the visible and persistence in the near-infrared bands. Once these issues are addressed and the extended emission from LSB objects is preserved by the data-processing pipeline, the Euclid Wide Survey will allow for studies of the Local Universe to be extended to statistical ensembles over a large part of the extragalactic sky.