Subhaloes in scale-free cosmologies

Pascal J. Elahi, Robert J. Thacker, Lawrence M. Widrow, Evan Scannapieco

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


We explore the dependence of the subhalo mass function on the spectral index n of the linear matter power spectrum using scale-free Einstein-de Sitter simulations with n = -1 and -2.5. We carefully consider finite volume effects that may call into question previous simulations of n < -2 power spectra. Subhaloes are found using a 6D friends-of-friends algorithm in all haloes originating from high-σ peaks. For n = -1, we find that the cumulative subhalo mass function is independent of the parameters used in the subhalo finding algorithm and is consistent with the subhalo mass function found in Λ cold dark matter (ΛCDM) simulations. In particular, the subhalo mass function is well fit by a power-law with an index of α = -0.9, that is the mass function has roughly equal mass in subhaloes per logarithmic interval in subhalo mass. Conversely, for n = -2.5, the algorithm parameters affect the subhalo mass function since subhaloes are more triaxial with less well-defined boundaries. We find that the index α is generally larger with α ≳ -0.75. We infer that although the subhalo mass function appears to be independent of n so long as n ≳ -2, it begins to flatten as n → -3. Thus, the common practice of using α ≈ -1.0 may greatly overestimate the number of subhaloes at the smallest scales in the CDM hierarchy.

Original languageEnglish (US)
Pages (from-to)1950-1962
Number of pages13
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
StatePublished - Jun 2009


  • Dark matter
  • Galaxies: haloes
  • Methods: N-body simulations
  • Methods: numerical

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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