2025/05/09 by Pascale, R., Calura, F., Vesperini, E. +10 · 1 citation
#Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences
paper · doi:10.48550/arxiv.2505.06346
The formation of compact high-redshift star-forming clumps, the physical processes driving their evolution and their potential connection to present-day Globular Clusters are key open questions in 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 sub-parsec resolution specifically designed to investigate the physical conditions behind the origin of compact stellar systems in high-redshift environments. The simulation object of this study focuses on a dwarf galaxy with a virial mass of a few 109 M_\odot 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, a setup 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_\odot pc-2, and masses predominantly spanning from 103 M_\odot to several 104 M_\odot, with a few reaching 105 M_\odot and up to 106 M_\odot. All clumps form during intense, short bursts of star formation lasting less than a Myr, often with negligible dark matter content (dark-to-stellar mass ratios below 1 within three times their effective radii). We measure a clear correlation between mass and size, and a clump mass function described by a power-law with a slope of -2. Star formation conditions in the simulation behave similarly to those of a feedback-free starburst scenario, where dense clumps form due to inefficient stellar feedback over small timescales. Notably, some clumps exhibit properties closely resembling those of present-day globular clusters.