Formation of globular cluster candidates in merging proto-galaxies at high redshift: a view from the FIRE cosmological simulations

• Published in: Monthly notices of the Royal Astronomical Society 2018-03, Vol.474 (3), p.4232-4244
• Main Authors: Kim, Ji-hoon, Ma, Xiangcheng, Grudić, Michael Y, Hopkins, Philip F, Hayward, Christopher C, Wetzel, Andrew, Faucher-Giguère, Claude-André, Kereš, Dušan, Garrison-Kimmel, Shea, Murray, Norman
• Format: Article
• Language: English
• Subjects: Feedback; Globular clusters; Interstellar matter; Metallicity; Protogalaxies; Red shift; Simulation; Star & galaxy formation; Star clusters; Star formation
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stx2994

Abstract Using a state-of-the-art cosmological simulation of merging proto-galaxies at high redshift from the FIRE project, with explicit treatments of star formation and stellar feedback in the interstellar medium, we investigate the formation of star clusters and examine one of the formation hypotheses of present-day metal-poor globular clusters. We find that frequent mergers in high-redshift proto-galaxies could provide a fertile environment to produce long-lasting bound star clusters. The violent merger event disturbs the gravitational potential and pushes a large gas mass of ≳ 105–6 M⊙ collectively to high density, at which point it rapidly turns into stars before stellar feedback can stop star formation. The high dynamic range of the reported simulation is critical in realizing such dense star-forming clouds with a small dynamical time-scale, tff ≲ 3 Myr, shorter than most stellar feedback time-scales. Our simulation then allows us to trace how clusters could become virialized and tightly bound to survive for up to ∼420 Myr till the end of the simulation. Because the cluster's tightly bound core was formed in one short burst, and the nearby older stars originally grouped with the cluster tend to be preferentially removed, at the end of the simulation the cluster has a small age spread.