Issue |
A&A
Volume 699, July 2025
|
|
---|---|---|
Article Number | A31 | |
Number of page(s) | 18 | |
Section | Galactic structure, stellar clusters and populations | |
DOI | https://doi.org/10.1051/0004-6361/202453252 | |
Published online | 27 June 2025 |
SIEGE
IV. Compact star clusters in cosmological simulations with a high star formation efficiency and subparsec resolution
1
INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna,
Via Gobetti 93/3,
40129
Bologna,
Italy
2
Department of Astronomy, Indiana University, Bloomington,
Swain West, 727 E. 3rd Street,
IN
47405,
USA
3
Centre de Recherche Astrophysique de Lyon UMR5574, Univ Lyon, Univ Lyon1, Ens de Lyon, CNRS,
69230
Saint-Genis-Laval,
France
4
Dipartimento di Fisica e Astronomia ‘Augusto Righi’, Università di Bologna,
via Piero Gobetti 93/2,
40129
Bologna,
Italy
5
Physics and Astronomy Department Galileo Galilei, University of Padova,
Vicolo dell’Osservatorio 3,
35122,
Padova,
Italy
6
INFN – Padova,
Via Marzolo 8,
35131
Padova,
Italy
7
Institut für Theoretische Astrophysik, ZAH, Universität Heidelberg,
Albert-Ueberle-Straße 2,
69120
Heidelberg,
Germany
8
Como Lake Center for Astrophysics (CLAP), DiSAT, Università degli Studi dell’Insubria,
via Valleggio 11,
22100
Como,
Italy
★ Corresponding author: raffaele.pascale@inaf.it
Received:
2
December
2024
Accepted:
6
May
2025
The formation of compact high-redshift star-forming clumps, along with the physical processes driving their evolution and their potential connection to present-day globular clusters (GCs), are key open questions in studies of galaxy formation. In this work, we aim to shed light on these aspects using the SImulating the Environment where Globular clusters Emerged (SIEGE) project, a suite of cosmological zoom-in simulations with subparsec resolution that is specifically designed to investigate the physical conditions behind the origin of compact stellar systems in high-redshift environments. The simulations analyzed in this study are focused on a dwarf galaxy with a virial mass of a few 109 M⊙ at z = 6.14, where the spatial resolution reaches 0.3 pc h−1. Individual stars are formed directly by sampling the initial mass function, with a 100% star formation efficiency. This setup is designed to explore the impact of a high star formation efficiency under high-redshift conditions. The simulation reveals the emergence of numerous stellar clumps with sizes of 1–3 pc, stellar surface densities up to almost 104 M⊙ pc−2, and masses predominantly spanning 103 M⊙ to several 104 M⊙, with a few reaching 105 M⊙ and up to 106 M⊙. All clumps form during intense, short bursts of star formation lasting less than a megayear, without noticeable signs of second peaks of star formation or accretion, often with negligible dark matter content (i.e., dark-to-stellar mass ratios below 1 within three times their effective radii). We measured a clear correlation between mass and size, with a clump mass function described by a power law with a slope of −2. Star formation conditions in the simulation reveal a behaviour that is similar to that of a feedback-free starburst scenario, where dense clumps form due to inefficient stellar feedback over small timescales. Notably, some clumps exhibit properties that closely resemble those of present-day globular clusters, highlighting their potential evolutionary connection.
Key words: globular clusters: general / galaxies: formation / galaxies: high-redshift / galaxies: kinematics and dynamics / galaxies: star formation / early Universe
© The Authors 2025
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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