Globular clusters in cosmological simulations and in lensed fields: from their birth to the present epoch

Abstract

Globular clusters in cosmological simulations and in lensed fields: from their birth to the present epoch. Following up on a state-of-the-art, existing set of high-resolution cosmological simulations, we aim to design a new model of a Milky-Way halo with unprecedented features. The new simulations will have sub-parsec resolution down to redshift z~2 and will be among the first in a fully cosmological framework including the feedback of individual stars. At later epochs, the evolution of the system will be followed by means of a cosmological, pure N-body simulation, which will be enough for a realistic description of the dynamical evolution of its sub-systems, in particular the globular clusters. We will compare the structural properties of the simulated clusters (i.e. magnitudes, density and sizes) with a wealth of multiwavelength observational data of the ancestors of present-day GCs in lensed fields. We will create lensed mock images of the simulated objects, a process that will be key for a reliable comparison between our high-level, proprietary data and simulations. We will study the chemical abundance pattern and the kinematical properties of the simulated clusters and compare them with local GCs. ACHIEVED RESULTS:

Risultati raggiunti

PRIN 2022 "Globular clusters in cosmological simulations and in lensed fields: from their birth to the present epoch" PI: Francesco Calura; PI-locale-UniBO: Carlo Nipoti The scientific activity supported by the project has combined theoretical modelling and observational studies aimed at understanding the formation and evolution of dense stellar systems and star-forming structures across cosmic time. A central theme of the project has been the investigation of compact star clusters and star-forming clumps in high-redshift galaxies, combining high-resolution simulations with the unprecedented observational capabilities of James Webb Space Telescope (JWST) and strong gravitational lensing. On the theoretical side, a major effort has focused on the formation of dense stellar systems in the early Universe, explored through high-resolution cosmological simulations. In particular, the SIEGE simulation suite has investigated the formation of compact star clusters in the first billion years of cosmic history using sub-parsec resolution and physically motivated stellar feedback models. These simulations demonstrate that extremely dense stellar systems can naturally emerge in early galaxies and may represent the progenitors of present-day globular clusters (Calura et al. 2025; Pascale et al. 2025). Additional work has addressed the fundamental physics regulating star formation, including analyses of gravitational instability in gaseous systems and galactic discs (Nipoti et al. 2024; Bacchini et al. 2024; Nipoti 2026), as well as studies of stellar feedback processes in dense stellar systems (Yaghoobi et al. 2024; Lacchin et al. 2025). Together, these works provide a theoretical framework linking gas collapse, feedback, and the emergence of compact stellar structures in young galaxies. Another important question addressed during the project is the dynamical evolution, down to the present day, of the higher-redshift compact stellar clusters observed thanks to gravitational lensing. In Giunchi et al. (2025) we studied in detail the specific case of the clusters observed in the so-called Sparkler Galaxy at redshift ≈1.4. The observational component of the project has focused on the detection and characterization of extremely compact star-forming structures in strongly lensed high-redshift galaxies, which allow spatial scales of a few parsecs to be probed in the early Universe. Exploiting the magnification provided by massive galaxy clusters, several studies have revealed populations of compact star clusters and star-forming clumps in galaxies during the first billion years of cosmic history. In particular, observations of lensed systems have enabled the identification of extremely compact and metal-poor star-forming regions with intense ionizing radiation (Vanzella et al. 2024), as well as detailed studies of the internal structure of high-redshift galaxies down to parsec scales (Messa et al. 2025). Further analyses of strongly lensed galaxies have provided insights into the nature of early star-forming systems and their ionizing properties (Messa et al. 2025; Vanzella et al. 2026), while spectroscopic and multiwavelength studies have revealed compact star-forming clumps and their physical conditions at high redshift Universe (Zanella et al. 2024). These works demonstrate that gravitational lensing combined with JWST and ALMA observations offer a unique laboratory for studying the small-scale structure of distant galaxies and the formation of stellar clusters at high redshift. The combined theoretical and observational effort has therefore provided a coherent picture in which compact star clusters and star-forming clumps represent fundamental building blocks of early galaxies, linking the physical processes of gas collapse and feedback with the observable properties of galaxies in the first billion years of cosmic history. References - Bacchini, C., Nipoti, C., Iorio, G., Roman-Oliveira, F., Rizzo, F., Mancera Piña, P. E., Marasco, A., Zanella, A., & Lelli, F. 2024, A&A;, 687, A115 - Calura, F., Pascale, R., Agertz, O., Andersson, E., Lacchin, E., Lupi, A., Meneghetti, M., Nipoti, C., Ragagnin, A., Rosdahl, J. et al. 2025, A&A;, 698, A207 - Giunchi E., Marinacci F., Nipoti C., Claeyssens A., Pascale R., Calura F., Ragagnin A., 2025, A&A;, 701, A129 - Lacchin, E., Donati, M., Calura, F., Nipoti, C., Lupi, A., & Yaghoobi, A. 2025, arXiv e-prints, arXiv:2511.09719 - Messa, M., Vanzella, E., Bergamini, P., Castellano, M., Sun, B., Willott, C., Windhorst, R. A., Yan, H., Angora, G., Rosati, P. et al. 2025, A&A;, 694, A59 - Nipoti, C., Caprioglio, C., & Bacchini, C. 2024, A&A;, 689, A61 - Nipoti, C. 2026, A&A;, 706, A238 - Pascale, R., Calura, F., Vesperini, E., Rosdahl, J., Nipoti, C., Giunchi, E., Lacchin, E., Lupi, A., Messa, M., Meneghetti M. et al. 2025, A&A;, 699, A31 - Vanzella, E., Loiacono, F., Messa, M., Castellano, M., Bergamini, P., Zanella, A., Annibali, F., Sun, B., Dickinson, M., Adamo A. et al. 2024, A&A;, 691, A251 - Yaghoobi, A., Rosdahl, J., Calura, F., & Ataiee, S. 2024, MNRAS, 528, 5477 - Zanella, A., Iani, E., Dessauges-Zavadsky, M., Richard, J., De Breuck, C., Vernet, J., Kohandel, M., Arrigoni Battaia, F., Bolamperti, A., Calura, F. et al. 2024, A&A;, 685, A80

Project details

Unibo Team Leader: Carlo Nipoti

Unibo involved Department/s:
Dipartimento di Fisica e Astronomia "Augusto Righi"

Coordinator:
Inaf - Istituto Nazionale Astrofisica(Italy)

Total Unibo Contribution: Euro (EUR) 72.107,00
Project Duration in months: 24
Start Date: 28/09/2023
End Date: 28/02/2026