Euclid: Star clusters in IC 342, NGC 2403, and Holmberg II
Abstract
We examine the star cluster populations in the three nearby galaxies IC 342, NGC 2403, and Holmberg II, observed as part of the Euclid Early Release Observations programme. Our main focus is on old globular clusters (GCs), for which the wide field-of-view and excellent image quality of Euclid offer substantial advantages over previous work. For IC 342 this is the first study of stellar clusters other than its nuclear cluster. After selection based on size and magnitude criteria, followed by visual inspection, we identify 111 old (> 1 Gyr) GC candidates in IC 342, 50 in NGC 2403 (of which 15 were previously known), and 7 in Holmberg II. In addition, a number of younger and/or intermediate-age candidates are identified. The colour distributions of GC candidates in the two larger galaxies show hints of bimodality with peaks at IE-HE = 0.36 and 0.79 (IC 342) and IE-HE = 0.36 and 0.80 (NGC 2403), corresponding to metallicities of [Fe/H]=-1.5 and [Fe/H]=-0.5, similar to those of 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). The excess objects may be similar to those previously identified in other galaxies. The specific frequency of classical old GCs in IC 342, as determined based on the brighter half of the GCLF, appears to be unusually low with SN=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, dN/dL ~ L^(-2.3+/-0.1) and the total numbers of young clusters brighter than M(IE)=-8 in NGC 2403 and Holmberg II are comparable with those found in their Local Group counterparts, that is, M33 and the Small Magellanic Cloud, respectively.
Cite
@article{arxiv.2503.16637,
title = {Euclid: Star clusters in IC 342, NGC 2403, and Holmberg II},
author = {S. S. Larsen and A. M. N. Ferguson and J. M. Howell and F. Annibali and J. -C. Cuillandre and L. K. Hunt and A. Lançon and T. Saifollahi and D. Massari and M. N. Le and N. Aghanim and B. Altieri and A. Amara and S. Andreon and N. Auricchio and C. Baccigalupi and M. Baldi and A. Balestra and S. Bardelli and P. Battaglia and A. Biviano and E. Branchini and M. Brescia and J. Brinchmann and S. Camera and V. Capobianco and C. Carbone and J. Carretero and S. Casas and M. Castellano and G. Castignani and S. Cavuoti and K. C. Chambers and A. Cimatti and C. Colodro-Conde and G. Congedo and C. J. Conselice and L. Conversi and Y. Copin and F. Courbin and H. M. Courtois and M. Cropper and A. Da Silva and H. Degaudenzi and G. De Lucia and H. Dole and M. Douspis and F. Dubath and X. Dupac and S. Dusini and S. Escoffier and M. Fabricius and M. Farina and F. Faustini and S. Ferriol and S. Fotopoulou and M. Frailis and E. Franceschi and S. Galeotta and K. George and B. Gillis and C. Giocoli and P. Gómez-Alvarez and J. Gracia-Carpio and A. Grazian and F. Grupp and S. V. H. Haugan and H. Hoekstra and W. Holmes and F. Hormuth and A. Hornstrup and K. Jahnke and M. Jhabvala and E. Keihänen and S. Kermiche and A. Kiessling and R. Kohley and B. Kubik and K. Kuijken and M. Kümmel and M. Kunz and H. Kurki-Suonio and A. M. C. Le Brun and S. Ligori and P. B. Lilje and V. Lindholm and I. Lloro and D. Maino and E. Maiorano and O. Mansutti and O. Marggraf and K. Markovic and M. Martinelli and N. Martinet and F. Marulli and R. Massey and E. Medinaceli and S. Mei and Y. Mellier and M. Meneghetti and G. Meylan and A. Mora and M. Moresco and L. Moscardini and C. Neissner and S. -M. Niemi and C. Padilla and S. Paltani and F. Pasian and K. Pedersen and W. J. Percival and V. Pettorino and S. Pires and G. Polenta and M. Poncet and L. A. Popa and L. Pozzetti and F. Raison and A. Renzi and J. Rhodes and G. Riccio and E. Romelli and M. Roncarelli and R. Saglia and Z. Sakr and D. Sapone and B. Sartoris and J. A. Schewtschenko and M. Schirmer and P. Schneider and A. Secroun and G. Seidel and M. Seiffert and S. Serrano and P. Simon and C. Sirignano and G. Sirri and J. Skottfelt and L. Stanco and J. Steinwagner and P. Tallada-Crespí and A. N. Taylor and I. Tereno and R. Toledo-Moreo and F. Torradeflot and A. Tsyganov and I. Tutusaus and L. Valenziano and J. Valiviita and T. Vassallo and G. Verdoes Kleijn and A. Veropalumbo and Y. Wang and J. Weller and G. Zamorani and F. M. Zerbi and E. Zucca and J. Martín-Fleitas and V. Scottez},
journal= {arXiv preprint arXiv:2503.16637},
year = {2025}
}
Comments
Submitted to A&A following internal review