3D Spectroscopy with VLT/GIRAFFE - IV: Angular Momentum and Dynamical Support of Intermediate Redshift Galaxies

TL;DR

This study investigates the evolution of angular momentum in intermediate redshift galaxies, revealing that their properties are similar to local disks and supporting a spiral rebuilding scenario through mergers over the last 8 billion years.

Contribution

It provides observational evidence for the non-linear evolution of galaxy angular momentum and compares distant and local galaxy kinematics to understand galaxy formation.

Findings

Distant rotating disks have similar angular momentum and size as local disks.

Galaxies with complex kinematics show higher scatter in angular momentum and size relations.

Evidence suggests angular momentum evolves via a non-linear random walk, influenced by mergers.

Abstract

[Abridged] One of the most outstanding problems related to numerical models of galaxy formation is the so-called ``angular momentum catastrophe''. We study the evolution of the angular momentum from z~0.6 to z=0 to further our understanding of the mechanisms responsible for the large angular momenta of disk galaxies observed today. This study is based on a complete sample of 32, 0.4<z<0.75 galaxies observed with FLAMES/GIRAFFE at the VLT. Their kinematics had been classified as rotating disks, perturbed rotators, or complex kinematics .We have computed the specific angular momentum of disks (j_disk) and the dynamical support of rotating disks through the V/sigma ratio. To study how angular momentum can be acquired dynamically, we have compared the properties of distant and local galaxies. We find that distant rotating disks have essentially the same properties (j_disk and R_d) as local disks, while distant galaxies with more complex kinematics have a significantly higher scatter in the j_disk--V_max and R_d--V_max planes. On average, distant galaxies show lower values of V/sigma than local galaxies. We found observational evidence for a non-linear random walk evolution of the angular momentum in galaxies during the last 8 Gyr. The evolution related to galaxies with complex kinematics can be attributed to mergers. If galaxies observed at intermediate redshift are related to present-day spirals, then our results fit quite well with the ``spiral rebuilding'' scenario proposed by Hammer et al. (2005)