Lopsidedness of self-consistent galaxies caused by the external field effect of clusters

Xufen Wu, Yougang Wang, Martin Feix, Hong Sheng Zhao

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)


Adopting Schwarzschild's orbit-superposition technique, we construct a series of self-consistent galaxy models, embedded in the external field of galaxy clusters in the framework of Milgrom's MOdified Newtonian Dynamics (MOND). These models represent relatively massive ellipticals with a Hernquist radial profile at various distances from the cluster center. Using N-body simulations, we perform a first analysis of these models and their evolution. We find that self-gravitating axisymmetric density models, even under a weak external field, lose their symmetry by instability and generally evolve to triaxial configurations. A kinematic analysis suggests that the instability originates from both box and nonclassified orbits with low angular momentum. We also consider a self-consistent isolated system that is then placed in a strong external field and allowed to evolve freely. This model, just like the corresponding equilibrium model in the same external field, eventually settles to a triaxial equilibrium as well, but has a higher velocity radial anisotropy and is rounder. The presence of an external field in the MOND universe generically predicts some lopsidedness of galaxy shapes.

Original languageEnglish
Article number130
Number of pages23
JournalAstrophysical Journal
Issue number2
Early online date31 Jul 2017
Publication statusPublished - 1 Aug 2017


  • Galaxies: elliptical and lenticular, cD
  • Galaxies: kinematics and dynamics
  • Gravitation
  • Methods: numerical


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