On the segregation of dark matter substructure

Frank C. Van den Bosch, Fangzhou Jiang, Duncan Campbell, Peter Behroozi

Research output: Contribution to journalArticlepeer-review

33 Scopus citations


We present the first comprehensive analysis of the segregation of dark matter subhaloes in their host haloes. Using three different numerical simulations, and two different segregation strength indicators, we examine the segregation of 12 different subhalo properties with respect to both orbital energy and halocentric radius (in real space as well as in projection). Subhaloes are strongly segregated by accretion redshift, which is an outcome of the inside-out assembly of their host haloes. Since subhaloes that were accreted earlier have experienced more tidal stripping, subhaloes that have lost a larger fraction of their mass at infall are on more bound orbits. Subhaloes are also strongly segregated in their masses and maximum circular velocities at accretion. We demonstrate that part of this segregation is already imprinted in the infall conditions. For massive subhaloes, it is subsequently boosted by dynamical friction, but only during their first radial orbit. The impact of these two effects is counterbalanced, though, by the fact that subhaloes with larger accretion masses are accreted later. Because of tidal stripping, subhaloes reveal little to no segregation by present-day mass or maximum circular velocity, while the corresponding torques cause subhaloes on more bound orbits to have smaller spin. There is a weak tendency for subhaloes that formed earlier to be segregated towards the centre of their host halo, which is an indirect consequence of the fact that (sub)halo formation time is correlated with other, strongly segregated properties. We discuss the implications of our results for the segregation of satellite galaxies in galaxy groups and clusters.

Original languageEnglish (US)
Pages (from-to)158-177
Number of pages20
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - Jan 1 2016
Externally publishedYes


  • Analytical
  • Dark matter
  • Formation
  • Galaxies
  • Galaxies
  • Galaxies
  • Haloes
  • Kinematics and dynamics
  • Methods
  • Methods
  • Statistical

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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