2025/03/11 by Fred Angelo Batan Garcia, Massimo Ricotti, Garcia, Fred Angelo Batan +3 · 1 voice · 2 citations
Physics and Astronomy · #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences
paper · doi:10.48550/arxiv.2503.08779
We model the formation of star clusters in a dwarf galaxy progenitor during the first 700 ~\rm Myr of cosmic history using a cosmological radiation-hydrodynamic simulation with a sub-grid star formation efficiency (SFE) model calibrated from AU-scale radiation-MHD simulations of molecular clouds with varying mass, density, and metallicity. In comparison to a constant SFE model, our model yields more bursty star formation, a more abundant massive star cluster population, and overall a higher stellar mass. Clouds reach SFEs up to 80%, forming bound star clusters (densities ∼102-4 ~\rm M_\odot pc-2, radii \lesssim 3~\rm pc) resembling those observed by the James Webb Space Telescope (JWST) in strongly lensed galaxies. Star clusters follow a flat power-law mass function \rm dN/\rm dlog M ∝ MΓ with slope Γ∼ -0.4. The most massive star clusters (104-5 ~\rm M_\odot) grow through mergers and have metallicity spreads of 0.05 - 0.1 dex that roughly scale with mass. The second burst of star formation produce loosely bound star clusters with higher metallicities: -1.95 < log(Z/\rm Z_\odot) < -1.50 at lower SFEs (2 - 20%). At z ∼ 8.7, a nuclear star cluster (NSC) is seeded, growing 83% of its mass ( 2.4 × 105 ~\rm M_\odot, 20% of the galaxy's stellar mass) through mergers with pre-existing clusters and the rest through in-situ star formation. The early formation of NSCs has interesting implications for seeding supermassive black holes and the population of little red dots recently discovered by JWST at z \gtrsim 5