Assembly Histories and Observational Properties of Simulated Early-type Galaxies

TL;DR

This paper uses simulations to show that massive early-type galaxies grow in two phases, with initial in situ star formation followed by accretion, explaining observed properties like color bimodality and kinematic diversity.

Contribution

It introduces a two-phase assembly model for massive galaxies, linking formation history to observed properties and feedback effects.

Findings

Massive galaxies assemble in two phases: in situ formation and accretion.

Gravitational feedback suppresses late star formation, explaining color bimodality.

Assembly history correlates with galaxy kinematic properties.

Abstract

We demonstrate that massive simulated galaxies assemble in two phases, with the initial growth dominated by compact in situ star formation, whereas the late growth is dominated by accretion of old stars formed in subunits outside the main galaxy. We also show that 1) gravitational feedback strongly suppresses late star formation in massive galaxies contributing to the observed galaxy colour bimodality that 2) the observed galaxy downsizing can be explained naturally in the two-phased model and finally that 3) the details of the assembly histories of massive galaxies are directly connected to their observed kinematic properties.