Self-similar solutions of triaxial dark matter halos

Yoram Lithwick, Neal Dalal

Research output: Contribution to journalArticlepeer-review


We investigate the collapse and the internal structure of dark matter halos. We consider halo formation from initially scale-free perturbations, for which gravitational collapse is self-similar. Fillmore & Goldreich and Bertschinger solved the one-dimensional (i.e., spherically symmetric) case. We generalize their results by formulating the three-dimensional self-similar equations. We solve the equations numerically and analyze the similarity solutions in detail, focusing on the internal density profiles of the collapsed halos. By decomposing the total density into subprofiles of particles that collapse coevally, we identify two effects as the main determinants of the internal density structure of halos: adiabatic contraction and the shape of a subprofile shortly after collapse; the latter largely reflects the triaxiality of the subprofile. We develop a simple model that describes the results of our three-dimensional simulations. In a companion paper, we apply this model to more realistic cosmological fluctuations, and thereby explain the origin of the nearly universal (NFW-like) density profiles found in N-body simulations.

Original languageEnglish (US)
Article number100
JournalAstrophysical Journal
Issue number2
StatePublished - Jun 10 2011


  • dark matter
  • galaxies: halos

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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