Direct detection of cold dark matter substructure

N. Dalal, C. S. Kochanek

Research output: Contribution to journalArticlepeer-review


We devise a method to measure the abundance of satellite halos in gravitational lens galaxies and apply our method to a sample of seven lens systems. After using Monte Carlo simulations to verify the method, we find that substructure comprises fsat = 0.02 (median, 0.006 < fsat < 0.07 at 90% confidence) of the mass of typical lens galaxies, in excellent agreement with predictions of cold dark matter (CDM) simulations. We estimate a characteristic critical radius for the satellites of 0.0001 < b < 0.006 (90% confidence). For a dn/dM ∝ M-1.8 (Mlow < M < Mhigh) satellite mass function, the critical radius provides an estimate for the upper mass limit of 106 M ≲ Mhigh ≲ 109 M. Our measurement confirms a generic prediction of CDM models and may obviate the need to invoke alternatives to CDM such as warm dark matter or self-interacting dark matter.

Original languageEnglish (US)
Pages (from-to)25-33
Number of pages9
JournalAstrophysical Journal
Issue number1 I
StatePublished - Jun 10 2002


  • Cosmology: theory
  • Dark matter
  • Galaxies: formation
  • Gravitational lensing
  • Large-scale structure of universe

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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