Fast and Slow Rotators: The build-up of the Red Sequence

TL;DR

This paper reveals that early-type galaxies are categorized as slow or fast rotators based on their angular momentum, which correlates with other physical properties and informs their evolutionary history on the red sequence.

Contribution

It introduces a clear classification of early-type galaxies based on angular momentum and links this to their formation processes and evolutionary pathways.

Findings

Galaxies are classified as slow or fast rotators based on specific angular momentum.

A link exists between angular momentum and galaxy mass sequence.

The build-up of the red sequence involves mergers and secular evolution.

Abstract

Using the unique dataset obtained within the course of the SAURON project, a radically new view of the structure, dynamics and stellar populations of early-type galaxies has emerged. We show that galaxies come in two broad flavours (slow and fast rotators), depending on whether or not they exhibit clear large-scale rotation, as indicated via a robust measure of the specific angular momentum of baryons. This property is also linked with other physical characteristics of early-type galaxies, such as: the presence of dynamically decoupled cores, orbital structure and anisotropy, stellar populations and dark matter content. I here report on the observed link between this baryonic angular momentum and a mass sequence, and how this uniquely relates to the building of the red sequence via dissipative/dissipationless mergers and secular evolution.