Evolving Gravitationally Unstable Disks Over Cosmic Time: Implications For Thick Disk Formation

TL;DR

This paper introduces a fast 1D simulation code to model galaxy evolution from z~2 to z~0, explaining the formation of thin and thick stellar disks through gravitational instability and evolving gas dynamics.

Contribution

The authors present a publicly available, efficient 1D simulation tool that tracks galaxy evolution, incorporating star formation and stellar heating effects, to explain disk galaxy structural features.

Findings

Gas velocity dispersion decreases from z~2 to z~0, influencing stellar populations.

The simulation reproduces the age-velocity dispersion relation observed locally.

High-redshift turbulence drives thick disk formation.

Abstract

Observations of disk galaxies at z~2 have demonstrated that turbulence driven by gravitational instability can dominate the energetics of the disk. We present a 1D simulation code, which we have made publicly available, that economically evolves these galaxies from z~2 to z~0 on a single CPU in a matter of minutes, tracking column density, metallicity, and velocity dispersions of gaseous and multiple stellar components. We include an H$_2$ regulated star formation law and the effects of stellar heating by transient spiral structure. We use this code to demonstrate a possible explanation for the existence of a thin and thick disk stellar population and the age-velocity dispersion correlation of stars in the solar neighborhood: the high velocity dispersion of gas in disks at z~2 decreases along with the cosmological accretion rate, while at lower redshift, the dynamically colder gas forms the low velocity dispersion stars of the thin disk.