Speaker
Description
Recent high-redshift observations from JWST and ALMA have revealed disc-like structures existing as early as redshift z ∼ 9. Some of these discs exhibit evidence of being dynamically cold, with rotation-to-dispersion support of Vrot/σ ≥ 4 at redshifts z > 4. These findings are in tension with predictions from cosmological simulations, as many struggle to reproduce dynamically cold discs at such high redshifts.
In this study, we explore the underlying physics driving the early formation of dynamically cold, Milky Way-like disc galaxies and their high-redshift predecessors. To do this, we employ high-resolution cosmological zoom-in simulations of Milky Way-mass disc galaxies from the VINTERGATAN suite.
Our simulations reveal the presence of disc-like structures at z > 4 and dynamically cold discs at z > 3, with the cold (T ≤ 100 K) gas tracing higher Vrot/σ values compared to the warm interstellar medium. This is in agreement with previous studies of different gas tracers and their influence on observed kinematics. Additionally, we see an overall trend of increasing Vrot/σ ratios as the redshift decreases. In order to obtain the observed high Vrot/σ > 10 values, we find that we need a stellar mass of M∗ > 10^10 M⊙, which is consistent with the estimated masses of the observed galaxies and other theoretical models. With a large fraction of the observed dynamically cold discs at high redshifts being massive galaxies, further studies of lower-mass high-z discs are essential to deepen our understanding of the evolution and kinematics of disc galaxies.
