Star cluster formation and survival in the first galaxies

Abstract

Using radiation-hydrodynamic cosmological simulations, we present a detailed (0.1 pc resolution), physically motivated portrait of a typical-mass dwarf galaxy before the epoch of reionization, resolving the formation and evolution of star clusters into individual $10\:\mathrm{{\rm M}_{\odot }}$ star particles. In the rest-frame UV, the galaxy has an irregular morphology with no bulge or disc, dominated by light emitted from numerous, compact, and gravitationally-bound star clusters. This is especially interesting in light of recent HST and JWST observations that – aided by the magnifying power of gravitational lenses – have imaged, at parsec-scale resolution, individual young star clusters forming in similar galaxies at z > 6. Because of their low metallicities and high temperatures, star-forming gas clouds in this galaxy have densities ∼100 times higher than typical giant molecular clouds; hence, their expected star formation efficiencies (SFEs) are high enough (around 10 − 70 per cent) to produce a sizeable population of potential globular cluster progenitors, but typically smaller (a few $100\:-\: 2\times 10^4\:\mathrm{{\rm M}_{\odot }}$, half-mass radii of up to 3 pc) and of lower metallicities (10−3.5 − 10−2.5 Z⊙). The initial mass function of the star-forming clouds is log-normal, while the bound star cluster mass function is a power-law with a slope that depends mainly on SFE but also on the temporal proximity to a major starburst. We find slopes between −0.5 and −2.5 depending on the assumed sub-grid SFE. Star formation is self-regulated on galactic scales; however, the multi-modal metallicity distribution of the star clusters and the fraction of stars locked into surviving bound star clusters depends on SFE.

The Extended [C ii] under Construction? Observation of the Brightest High-z Lensed Star-forming Galaxy at z = 6.2

“…, which is >6000 times larger than that of giant molecular clouds in today's ISM (e.g., Leroy et al 2008), and ×100 higher than the maximum value found in the recent simulation of galaxies at z ∼ 8 (Garcia et al 2023).…”

Formation of Massive and Wide First-star Binaries in Radiation Hydrodynamic Simulations

“…First, the reduction in the individual masses of Population III stars should change their role in driving the subsequent evolution of the Universe through stellar radiation, supernovae, and seeding BHs that might rapidly grow into supermassive BHs (see, e.g., Sugimura et al 2017Sugimura et al , 2018Sugimura & Ricotti 2020, and references therein). Incorporating our findings into cosmological simulations of galaxy formation is crucial for unveiling the early evolution of the Universe (see, e.g., Garcia et al 2023).…”

The Impact of Stellar Radiative Feedback on Formation of Young Massive Clusters via Fast H i Gas Collisions

“…In addition, recent observations by the James Webb Space Telescope suggest that early galaxies at redshifts of approximately z ∼ 4-10 form at least 10% to 30% of their stars within YMCs (e.g., Vanzella et al 2022Vanzella et al , 2023aVanzella et al , 2023bAdamo et al 2024). Additionally, numerical simulations indicate that massive star clusters are likely to form from warmer gas due to the combination of intense far-ultraviolet (FUV) radiation and low metallicity in the early Universe (Garcia et al 2023;Sugimura et al 2024). This demonstrates that understanding YMC formation is crucial for elucidating the star formation history of galaxies.…”