Stellar and Gaseous Disk Structures in Cosmological Galaxy Equilibrium Models

TL;DR

This paper develops radially-resolved equilibrium models for stellar and gaseous disks in massive, high-redshift halos, demonstrating how these disks naturally form exponential profiles and match observed galaxy properties.

Contribution

It introduces a new set of time-dependent, radially-resolved equilibrium models that incorporate star formation, inflows, outflows, and angular momentum conservation, providing insights into disk formation at redshift z~2.

Findings

Disks reach equilibrium on dynamical timescales.

Exponential disk profiles emerge naturally from conservation laws.

Models reproduce observed galaxy properties at z=2.

Abstract

We present "radially-resolved-equilibrium-models" for the growth of stellar and gaseous disks in cosmologically accreting massive halos. Our focus is on objects that evolve to redshifts $z\sim 2$. We solve the time-dependent equations that govern the radially dependent star-formation rates, inflows and outflows from and to the inter- and circum-galactic medium, and inward radial gas flows within the disks. The stellar and gaseous disks reach equilibrium configurations on dynamical time scales much shorter than variations in the cosmological dark matter halo growth and baryonic accretions rates. We show analytically that mass and global angular momentum conservation naturally give rise to exponential gas and stellar disks over many radial length scales. As expected, the gaseous disks are more extended as set by the condition Toomre $Q<1$ for star-formation. The disks rapidly become baryon dominated. For massive, $5\times 10^{12}M_\odot$ halos at redshift $z=2$, we reproduced the typical observed star-formation rates of $\sim 100 \, M_\odot \, {\rm yr}^{-1}$, stellar masses $\sim 9\times 10^{10}\, M_\odot$, gas contents $\sim 10^{11}\, M_\odot$, half mass sizes of 4.5 and 5.8 kpc for the stars and gas, and characteristic surface densities of $500$ and $ 400\, M_\odot \, {\rm pc}^{-2}$ for the stars and gas.