On the Evolution of the Velocity-Mass-Size Relations of Disk-Dominated Galaxies over the Past 10 Billion Years

TL;DR

This study investigates the evolution of key scaling relations in star-forming disk galaxies over the past 10 billion years, showing weak evolution consistent with galaxy formation models and correcting previous size measurement misconceptions.

Contribution

It provides a comprehensive analysis combining observational data and models to explain the evolution of galaxy scaling relations and addresses discrepancies in high-redshift galaxy size measurements.

Findings

Weak evolution of stellar and baryonic scaling relations from z~2 to 0.

Model predictions align with observed weak evolution of galaxy properties.

Corrected size measurements negate the need for high spin parameter hypotheses at high redshift.

Abstract

We study the evolution of the scaling relations between maximum circular velocity, stellar mass and optical half-light radius of star-forming disk-dominated galaxies in the context of LCDM-based galaxy formation models. Using data from the literature combined with new data from the DEEP2 and AEGIS surveys we show that there is a consistent observational and theoretical picture for the evolution of these scaling relations from z\sim 2 to z=0. The evolution of the observed stellar scaling relations is weaker than that of the virial scaling relations of dark matter haloes, which can be reproduced, both qualitatively and quantitatively, with a simple, cosmologically-motivated model for disk evolution inside growing NFW dark matter haloes. In this model optical half-light radii are smaller, both at fixed stellar mass and maximum circular velocity, at higher redshifts. This model also predicts that the scaling relations between baryonic quantities evolve even more weakly than the corresponding stellar relations. We emphasize, though, that this weak evolution does not imply that individual galaxies evolve weakly. On the contrary, individual galaxies grow strongly in mass, size and velocity, but in such a way that they move largely along the scaling relations. Finally, recent observations have claimed surprisingly large sizes for a number of star-forming disk galaxies at z \sim 2, which has caused some authors to suggest that high redshift disk galaxies have abnormally high spin parameters. However, we argue that the disk scale lengths in question have been systematically overestimated by a factor \sim 2, and that there is an offset of a factor \sim 1.4 between H\alpha sizes and optical sizes. Taking these effects into account, there is no indication that star forming galaxies at high redshifts (z\sim 2) have abnormally high spin parameters.