Balance among gravitational instability, star formation, and accretion determines the structure and evolution of disk galaxies

TL;DR

This paper presents a theoretical model explaining how the balance among gravitational instability, star formation, and accretion drives the structural evolution of disk galaxies over cosmic time, accounting for observed features from high-redshift to local galaxies.

Contribution

It introduces a comprehensive 1D disk evolution model that captures the transition from violent instability to secular galaxy evolution driven by physical process balances.

Findings

Galaxies maintain a slowly evolving equilibrium with balanced accretion, star formation, winds, and gravitational torques.

The model explains high velocity dispersions and clumpiness in z~2 galaxies.

It accounts for bulge growth, quenching, and gas profile features in local spirals.

Abstract

Over the past 10 Gyr, star-forming galaxies have changed dramatically, from clumpy and gas rich, to rather quiescent stellar-dominated disks with specific star formation rates lower by factors of a few tens. We present a general theoretical model for how this transition occurs, and what physical processes drive it, making use of 1D axisymmetric thin disk simulations with an improved version of the Gravitational Instability-Dominated Galaxy Evolution Tool (GIDGET) code. We show that at every radius galaxies tend to be in a slowly evolving equilibrium state wherein new accretion is balanced by star formation, galactic winds, and radial transport of gas through the disk by gravitational instability (GI) -driven torques. The gas surface density profile is determined by which of these terms are in balance at a given radius - direct accretion is balanced by star formation and galactic winds near galactic centers, and by transport at larger radii. We predict that galaxies undergo a smooth transition from a violent disk instability phase to secular evolution. This model provides a natural explanation for the high velocity dispersions and large clumps in z~2 galaxies, the growth and subsequent quenching of bulges, and features of the neutral gas profiles of local spiral galaxies.