66th Annual Reunion of the Argentinian Astronomy Association
Date:
In this study, we investigate scale relations during early cosmic epochs with a redshift 𝑧 ≳ 6 using the FirstLight cosmological simulation suite. This suite comprises 300 high-resolution zoom-ins and accurately depicts the reionization of the large-scale intergalactic medium while resolving galaxy properties. We observe that the half-mass radius (rhm) of simulated galaxies shows a moderate increase with stellar mass at 𝑀∗ ≲ 108 M⊙, followed by a rapid decrease at higher masses. This reduction in galaxy size is predominantly observed in massive galaxies (𝑀∗ > 109 M⊙), which undergo a phase of rapid compaction and gas depletion. This leads to a contraction of the gaseous component into a compact star-forming phase, subsequently transitioning to central quenching of star formation and forming a compact passive stellar disc. Consequently, we identify positive correlations between galaxy sizes, specific star-formation rates, and gas abundances, marking a transition from diffuse, star-forming regions to compact, quenched structures with extended discs.