Antibias in clusters: The dependence of the mass-to-light ratio on cluster temperature

Neta A. Bahcall, Julia M. Comerford

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45 Scopus citations


We show that the observed mass-to-light (M/L) ratio of galaxy clusters increases with cluster temperature as expected from cosmological simulations. Contrary to previous observational suggestions, we find a mild but robust increase of MIL from poor (T ∼ 1-2 keV) to rich (T ∼ 12 keV) clusters; over this range, the mean M/Lv increases by a factor of about 2. The best-fit relation satisfies M/Lv = (170 ± 30)T kev0.3±0.1 h at z = 0, with a large scatter. This trend confirms predictions from cosmological simulations that show that the richest clusters are antibiased, with a higher ratio of mass per unit light than average. The antibias increases with cluster temperature. The effect is caused by the relatively older age of the high-density clusters, where light has declined more significantly than average since their earlier formation time. Combining the current observations with simulations, we find a global value of M/Lv = 240 ± 50 h and a corresponding mass density of the universe of Ωm = 0.17 ± 0.05.

Original languageEnglish (US)
Pages (from-to)L5-L8
JournalAstrophysical Journal
Issue number1 II
StatePublished - Jan 20 2002

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Cosmology: observations
  • Cosmology: theory
  • Dark matter
  • Galaxies: clusters: general
  • Large-scale structure of universe


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