Kinematic Evolution of Simulated Star-Forming Galaxies

TL;DR

This study compares state-of-the-art hydrodynamic galaxy simulations with observations, showing that simulated galaxies undergo kinematic evolution similar to real galaxies, supporting the disk settling process over the last 8 billion years.

Contribution

First comprehensive comparison of high-resolution cosmological galaxy simulations with observational kinematic data, validating simulation accuracy in galaxy evolution modeling.

Findings

Simulated galaxies show decreasing disordered motions over time.

Simulated galaxies exhibit increasing ordered rotation with time.

Kinematic trends in simulations match observational data.

Abstract

Recent observations have shown that star-forming galaxies like our own Milky Way evolve kinematically into ordered thin disks over the last ~8 billion years since z=1.2, undergoing a process of "disk settling." For the first time, we study the kinematic evolution of a suite of four state of the art "zoom in" hydrodynamic simulations of galaxy formation and evolution in a fully cosmological context and compare with these observations. Until now, robust measurements of the internal kinematics of simulated galaxies were lacking as the simulations suffered from low resolution, overproduction of stars, and overly massive bulges. The current generation of simulations has made great progress in overcoming these difficulties and is ready for a kinematic analysis. We show that simulated galaxies follow the same kinematic trends as real galaxies: they progressively decrease in disordered motions (sigma_g) and increase in ordered rotation (Vrot) with time. The slopes of the relations between both sigma_g and Vrot with redshift are consistent between the simulations and the observations. In addition, the morphologies of the simulated galaxies become less disturbed with time, also consistent with observations, and they both have similarly large scatter. This match between the simulated and observed trends is a significant success for the current generation of simulations, and a first step in determining the physical processes behind disk settling.