One Moment in Time-Modeling Star Formation in the Antennae

Research output: Contribution to journalArticle


We present a new high-resolution N-body/smoothed particle hydrodynamics simulation of an encounter of two gas-rich disk galaxies that closely matches the morphology and kinematics of the interacting Antennae galaxies (NGC 4038/39). The simulation includes radiative cooling, star formation, and feedback from Type II supernovae. 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 (Δt ≈ 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.


  • Simon J. Karl
  • Thorsten Naab
  • Peter H. Johansson
  • Hanna Kotarba
  • Christian M. Boily
  • Florent Renaud
  • Christian Theis
External organisations
  • Ludwig-Maximilian University of Munich
  • Max Planck Institute for Astrophysic
  • University of Strasbourg
  • University of Vienna
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Astronomy, Astrophysics and Cosmology


  • galaxies: evolution, galaxies: individual: NGC 4038/39, galaxies: interactions, galaxies: star formation, methods: numerical, Astrophysics - Cosmology and Nongalactic Astrophysics
Original languageEnglish
Pages (from-to)L88-L93
Number of pages6
Issue number2
Publication statusPublished - 2010 Jun 1
Publication categoryResearch
Externally publishedYes