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Oscar Agertz. Profile photo.

Oscar Agertz

Associate Professor / Senior university lecturer / Wallenberg Academy Fellow

Oscar Agertz. Profile photo.

EDGE : A new approach to suppressing numerical diffusion in adaptive mesh simulations of galaxy formation


  • Andrew Pontzen
  • Martin P. Rey
  • Corentin Cadiou
  • Oscar Agertz
  • Romain Teyssier
  • Justin Read
  • M. D. Orkney

Summary, in English

We introduce a new method to mitigate numerical diffusion in adaptive mesh refinement (AMR) simulations of cosmological galaxy formation, and study its impact on a simulated dwarf galaxy as part of the 'EDGE' project. The target galaxy has a maximum circular velocity of 21 km s-1 but evolves in a region that is moving at up to 90 km s-1 relative to the hydrodynamic grid. In the absence of any mitigation, diffusion softens the filaments feeding our galaxy. As a result, gas is unphysically held in the circumgalactic medium around the galaxy for 320 Myr, delaying the onset of star formation until cooling and collapse eventually triggers an initial starburst at z = 9. Using genetic modification, we produce 'velocity-zeroed' initial conditions in which the grid-relative streaming is strongly suppressed; by design, the change does not significantly modify the large-scale structure or dark matter accretion history. The resulting simulation recovers a more physical, gradual onset of star formation starting at z = 17. While the final stellar masses are nearly consistent (4.8 × 106 M⊙ and 4.4 × 106 M⊙ for unmodified and velocity-zeroed, respectively), the dynamical and morphological structure of the z = 0 dwarf galaxies are markedly different due to the contrasting histories. Our approach to diffusion suppression is suitable for any AMR zoom cosmological galaxy formation simulations, and is especially recommended for those of small galaxies at high redshift.


  • Lund Observatory - Has been reorganised
  • eSSENCE: The e-Science Collaboration

Publishing year







Monthly Notices of the Royal Astronomical Society





Document type

Journal article


Oxford University Press


  • Astronomy, Astrophysics and Cosmology


  • cosmology: miscellaneous
  • galaxies: dwarf
  • methods: numerical




  • ISSN: 0035-8711