Properties of disk galaxies in a hierarchical formation scenario

TL;DR

This paper models disk galaxy formation within a hierarchical framework, showing how initial cosmological factors influence galaxy properties and reproducing observed correlations and relations.

Contribution

It introduces a comprehensive hierarchical galaxy formation model that explains key disk galaxy properties and their correlations without adjustable star formation efficiency.

Findings

Disks have exponential profiles and flat rotation curves.

Color-magnitude and Tully-Fisher relations explained by dust absorption.

Models reproduce observed infrared Tully-Fisher and luminosity-radius relations.

Abstract

We used galaxy evolutionary models in a hierarchical inside-out formation scenario to study the origin of the main properties and correlations of disk galaxies. We found that most of these properties and correlations are the result of three (cosmological) initial factors and their dispersions: the virial mass, the halo mass aggregation history (MAH), and the angular momentum given through the spin parameter \lambda. The MAH determines mainly the halo structure and the color indexes while \lambda determines mainly the surface brightness and the bulge-to-disk ratio. We calculated star formation (SF) using a gravitational instability criterion and a self-regulation mechanism in the turbulent ISM. The efficiency of SF in this model is almost independent from the mass. We show that the luminosity-dependent dust absorption empirically determined by Wang & Heckman explains the observed color-magnitude and color Tully-Fisher (TF) relations without the necessity of introducing a mass-dependent SF efficiency. The disks in centrifugal equilibrium form within growing CDM halos with a gas accretion rate proportional to the MAH. The disks present exponential surface density and brightness profiles, negative radial color index gradients, and nearly flat rotation curves. We also calculated the secular formation of a bulge due to gravitational instabilities in the stellar disk. The intensive properties of our models agree with the observational data and the trends of the Hubble sequence are reproduced. The predicted infrared TF and luminosity-radius relations also agree with observations. The main shortcomings of our inside-out hierarchical models are the excessive radial color gradients and the dark halo dominion in the rotation curve decompositions.