One moment in time - modeling star formation in the Antennae

TL;DR

This study uses high-resolution simulations to model the Antennae galaxies' interaction, accurately reproducing observed features and revealing a brief, specific phase of starburst activity shortly after the second galactic encounter.

Contribution

The paper introduces a detailed N-body/SPH simulation that captures the timing and properties of star formation in the Antennae galaxies, explaining distributed star formation as a consequence of recent interaction.

Findings

Simulation matches observed morphology and kinematics.

Starburst phase occurs ~20 Myr after second encounter.

Antennae are in a later merger stage than the Mice.

Abstract

We present a new high-resolution N-body/SPH simulation of an encounter of two gas-rich disk galaxies which closely matches the morphology and kinematics of the interacting Antennae galaxies (NGC 4038/39). The simulation includes radiative cooling, star formation and feedback from SNII. The large-scale morphology and kinematics are determined by the internal structure and the orbit of the progenitor disks. The properties of the central region, in particular the starburst in the overlap region, only match the observations for a very short time interval of ~20 Myr after the second encounter. This indicates that the Antennae galaxies are in a special phase only about 40 Myr after the second encounter and 50 Myr before their final collision. This is the only phase in the simulation when a gas-rich overlap region between the nuclei is forming accompanied by enhanced star formation. The star formation rate as well as the recent star formation history in the central region agree well with observational estimates. For the first time this new model explains the distributed extra-nuclear star formation in the Antennae galaxies as a consequence of the recent second encounter. The proposed model predicts that the Antennae are in a later merger stage than the Mice (NGC 4676) and would therefore lose their first place in the classical Toomre sequence.