<i>Euclid</i> : Star clusters in IC 342, NGC 2403, and Holmberg II

We examine the star cluster populations in the three nearby (3.20–3.45 Mpc) galaxies IC 342, NGC 2403, and Holmberg II, observed as part of the Euclid Early Release Observations programme. Our main focus in this paper is old globular clusters (GCs), for which the wide field of view and excellent image quality of Euclid offer substantial advantages over previous works. With respect to IC 342, in particular, this is the first study of stellar clusters that goes beyond its nuclear cluster. After a selection process based on size and magnitude criteria, followed by visual inspection, we identified 111 old (≳1 Gyr) GC candidates in IC 342, 49 in NGC 2403 (of which 15 were previously known), along with 7 in Holmberg II. In addition, a number of younger and/or intermediate-age candidates were identified. The colour distributions of GC candidates in the two larger galaxies show hints of bimodality, with peaks at ( I E −{H E ) 0 = 0.36 and 0.79 in both IC 342 and NGC 2403, corresponding to metallicities of [Fe/H] ≈ −1.5 and [Fe/H] ≈ −0.5. These results are similar to those reported for the metal-poor and metal-rich GC subpopulations in the Milky Way. The luminosity functions of our GC candidates exhibit an excess of relatively faint objects, relative to a canonical, approximately Gaussian GC luminosity function (GCLF). Although some contamination from background galaxies and younger clusters might be present in our GC samples, we argue that the excess could be at least partially real. In particular, we find this could be the case for IC 342, where the excess objects could be similar to those previously identified, for example, in M101 and NGC 6946. The specific frequency of old GCs in IC 342, as determined on the basis of the brighter half of the GCLF, appears to be unusually low with S N ≈ 0.2–0.3. The combined luminosity function of young and intermediate-age clusters in all three galaxies is consistent with a power-law distribution of d N /d L ∝ L −2.3 ± 0.1 . The total numbers of young clusters brighter than M ( I E ) = −8 in NGC 2403 and Holmberg II are comparable with those found in their Local Group counterparts, namely, M33 and the Small Magellanic Cloud, respectively.

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Publication Details

Journal
Astronomy and Astrophysics
Published
2025-09-15
DOI
https://doi.org/10.1051/0004-6361/202554661
Citations
2
Primary Topic
Stellar, planetary, and galactic studies
Type
article
Field-Weighted Citation Impact
2.31
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article

Euclid : Star clusters in IC 342, NGC 2403, and Holmberg II

D Sapone, L. K. Hunt, S. S. Larsen, S Casas et al.
2 citations
Astronomy and Astrophysics
Stellar, planetary, and galactic studies
2.31
article

Euclid : Star clusters in IC 342, NGC 2403, and Holmberg II

D Sapone, L. K. Hunt, S. S. Larsen, S Casas, Will J. Percival, G. Riccio, J. Martín-Fleitas, G. Zamorani, I Tereno, G de Lucia, F. Dubath, J Brinchmann, M Kümmel, K. Markovic, S Ferriol, C. Giocoli, P. Schneider, Patrice Simon, S Dusini, M. Jhabvala, F Raison, S. Bardelli, O Marggraf, F Faustini, C. Padilla, G Castignani, K Jahnke, A. Secroun, J. Howell, T. Saifollahi, A. Kiessling, H Degaudenzi, S. Cavuoti, S. V. H. Haugan, M Fabricius, J. Skottfelt, A. Tsyganov, T. Vassallo, J.-C. Cuillandre, R. Toledo-Moreo, M. Moresco, G Seidel, G Congedo, L Moscardini, K George, F Grupp, H. Dole, C Colodro-Conde, J. Valiviita, B Gillis, L Stanco, Christopher J. Conselice, Henk Hoekstra, C. Colodro-Conde, E Medinaceli, B Sartoris, M. Douspis, F. Marulli, P. Tallada-Crespí, J. Väliviita, C Sirignano, M Frailis, J. Carretero, M. Martinelli, N. R. Napolitano, K. Pedersen, E Keihänen, E. Maiorano, A. Hornstrup, L. Conversi, S. Fotopoulou, F. Hormuth, R. Kohley, M. Giulietti, A. Lançon, F. M. Zerbi, A. Balestra, E. Branchini, A. M. N. Ferguson, M. Farina, F. Pasian, I Lloro, H Kurki-Suonio, J. Rhodes, A Amara, E. Franceschi, J.A Schewtschenko, ENRIQUE GAZTAÑAGA, M. Brescia, Konrad H. Kuijken, M Cropper, M. Schirmer, R Saglia, V Capobianco, Y. Mellier, J. Gracia-Carpio, M Castellano, C. Neissner, K. C. Chambers, V. Lindholm, M Roncarelli, G. Meylan, A da Silva, N. Auricchio, S Galeotta, P. Bergamini, S Camera, R Massey, E Zucca, Z. Sakr, F. Annibali, B. Altieri, S. Kermiche, M Baldi, G Sirri, O. Mansutti, P. B. Lilje, A.N. Taylor, N. Martinet, A Veropalumbo, L.A. Popa, A.M.C Le Brun, D. Massari, P. Gómez-Alvarez, H. M. Courtois, S Andreon, Yi Wang, M Kunz, M. D. Seiffert, I. Tutusaus, A. Cimatti, N. Aghanim, S.-M. Niemi, S. Paltani, V. Pettorino, S. Pires, S Serrano, E. Romelli, A Renzi, P Battaglia, X. Dupac, C. Baccigalupi, F Torradeflot, M. Poncet, S Mei, A Biviano, B. Kubik, W. Holmes, Y. Ascasíbar, G. Polenta, L Valenziano, M. N. Bremer, A. Mora, M.N Le, S Ligori
article en
2 citations

Abstract

We examine the star cluster populations in the three nearby (3.20–3.45 Mpc) galaxies IC 342, NGC 2403, and Holmberg II, observed as part of the Euclid Early Release Observations programme. Our main focus in this paper is old globular clusters (GCs), for which the wide field of view and excellent image quality of Euclid offer substantial advantages over previous works. With respect to IC 342, in particular, this is the first study of stellar clusters that goes beyond its nuclear cluster. After a selection process based on size and magnitude criteria, followed by visual inspection, we identified 111 old (≳1 Gyr) GC candidates in IC 342, 49 in NGC 2403 (of which 15 were previously known), along with 7 in Holmberg II. In addition, a number of younger and/or intermediate-age candidates were identified. The colour distributions of GC candidates in the two larger galaxies show hints of bimodality, with peaks at ( I E −{H E ) 0 = 0.36 and 0.79 in both IC 342 and NGC 2403, corresponding to metallicities of [Fe/H] ≈ −1.5 and [Fe/H] ≈ −0.5. These results are similar to those reported for the metal-poor and metal-rich GC subpopulations in the Milky Way. The luminosity functions of our GC candidates exhibit an excess of relatively faint objects, relative to a canonical, approximately Gaussian GC luminosity function (GCLF). Although some contamination from background galaxies and younger clusters might be present in our GC samples, we argue that the excess could be at least partially real. In particular, we find this could be the case for IC 342, where the excess objects could be similar to those previously identified, for example, in M101 and NGC 6946. The specific frequency of old GCs in IC 342, as determined on the basis of the brighter half of the GCLF, appears to be unusually low with S N ≈ 0.2–0.3. The combined luminosity function of young and intermediate-age clusters in all three galaxies is consistent with a power-law distribution of d N /d L ∝ L −2.3 ± 0.1 . The total numbers of young clusters brighter than M ( I E ) = −8 in NGC 2403 and Holmberg II are comparable with those found in their Local Group counterparts, namely, M33 and the Small Magellanic Cloud, respectively.

Astronomy and AstrophysicsVol. 703
Université Claude Bernard Lyon 1 (FR), University of Geneva (CH), Institució Catalana de Recerca i Estudis Avançats (ES), Leiden University (NL), California Institute of Technology (US), University of Copenhagen (DK), Centre National de la Recherche Scientifique (FR), Goddard Space Flight Center (US), University of Hawaii System (US), Jet Propulsion Laboratory (US), Université Toulouse III - Paul Sabatier (FR), University of Bonn (DE), Scuola Internazionale Superiore di Studi Avanzati (IT), University of Padua (IT), University of Lisbon (PT), Radboud University Nijmegen (NL), University of Waterloo (CA), Universidad de La Laguna (ES), University of Groningen (NL), Université Fédérale de Toulouse Midi-Pyrénées (FR), Lyon College (US), Université Catholique de Lille (FR), Universidade do Porto (PT), Perimeter Institute (CA), University of Oslo (NO), Institute for High Energy Physics (ES), University of Milan (IT), University of Saint Joseph (US), Université Paris Cité (FR), Aix-Marseille Université (FR), Heidelberg University (DE), Université de Lille (FR), Commissariat à l'Énergie Atomique et aux Énergies Alternatives (FR), Université Paris Sciences et Lettres (FR), Université Paris-Saclay (FR), Centre National d'Études Spatiales (FR), Arcetri Astrophysical Observatory (IT), Helsinki Institute of Physics (FI), Istituto Nazionale di Fisica Nucleare, Galileo Galilei Institute for Theoretical Physics (IT), Astronomical Observatory of Rome (IT), Trieste Astronomical Observatory (IT), Institut d'Astrophysique de Paris (FR), Astronomical Observatory of Capodimonte (IT), European Space Agency (FR), Laboratoire AstroParticule et Cosmologie (FR), Observatoire astronomique de Strasbourg (FR), Brera Astronomical Observatory (IT), University of Surrey (GB), United Kingdom Space Agency (GB), Universidad Politécnica de Cartagena (ES), University of Bristol (GB), Sorbonne Université (FR), Park University (US), Osservatorio astronomico di Bologna (IT), Astrophysique, Instrumentation et Modélisation (FR), Janssen (France) (FR), Laboratoire Univers et Théories (FR), Institute of Astrophysics and Space Sciences (PT), Max Planck Institute for Extraterrestrial Physics (DE), Institut d'Estudis Espacials de Catalunya (ES), Centre de physique des particules de Marseille (FR), Laboratoire d’Astrophysique de Marseille (FR), Istituto Nazionale di Fisica Nucleare, Sezione di Torino (IT), Institute for Space Astrophysics and Planetology (IT), Institut d'Astrophysique Spatiale (FR), International University of Beirut (LB), Institut Català de Ciències del Clima (ES), Istituto Nazionale di Fisica Nucleare, Sezione di Padova (IT), Osservatorio Astrofisico di Torino (IT), Royal Observatory (GB), SKA Observatory (GB), Istituto Nazionale di Fisica Nucleare, Sezione di Napoli (IT), Max Planck Institute for Astronomy (DE), Institute of Space Sciences (ES), Laboratoire de Physique Théorique (FR), DAWN Center for Independent Living (US), Château Gombert (FR), Federico II University Hospital (IT), Institute of Theoretical Physics (CN), Istituto Nazionale di Fisica Nucleare, Sezione di Genova (IT), CEA Paris-Saclay (FR), Naples Anesthesia & Physician Associates (US), Instituto de Astrofísica de Canarias (ES), Felix Scholarship (GB), Astronomical Institute of the Slovak Academy of Sciences (SK), Istituto Nazionale di Fisica Nucleare, Sezione di Milano (IT), Institute of Space Science - INFLPR Subsidiary (RO), Engineering Science Analysis (United States) (US), Fractal Systems (Canada) (CA), Istituto Nazionale di Fisica Nucleare, Sezione di Bologna (IT), Port d'Informació Científica (ES), Istituto Nazionale di Fisica Nucleare, Sezione di Trieste (IT), Institute for Fundamental Physics of the Universe (IT), Institute of Nuclear Physics of Lyon (FR), St. Joseph Medical Center (US), Istituto Nazionale di Fisica Nucleare, Sezione di Roma I (IT), Osservatorio Astronomico di Padova (IT), Bristol Robotics Laboratory (GB), European Space Research Institute (IT), Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (ES), Institut de Recherche en Astrophysique et Planétologie (FR), Infrared Processing and Analysis Center (US), Osservatorio di Astrofisica e Scienza dello Spazio, Institut de Physique des 2 Infinis de Lyon (FR), European Space Research and Technology Centre (NL), University College London (GB), École Polytechnique Fédérale de Lausanne (CH), University of Turin (IT), University of Chile (CL), Heidelberg Institute for Theoretical Studies (DE), Open University Malaysia (MY), Ludwig-Maximilians-Universität München (DE), University of Genoa (IT), National Institute for Astrophysics (IT), RWTH Aachen University (DE), University of Bologna (IT), Technical University of Denmark (DK), University of Edinburgh (GB)
Openalex Percentile: Top 10%
Stellar, planetary, and galactic studies
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