### Abstract

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/L_{v} increases by a factor of about 2. The best-fit relation satisfies M/L_{v} = (170 ± 30)T _{kev}^{0.3±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/L_{v} = 240 ± 50 h and a corresponding mass density of the universe of Ω_{m} = 0.17 ± 0.05.

Original language | English (US) |
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Pages (from-to) | L5-L8 |

Journal | Astrophysical Journal |

Volume | 565 |

Issue number | 1 II |

DOIs | |

State | Published - Jan 20 2002 |

### All Science Journal Classification (ASJC) codes

- Astronomy and Astrophysics
- Space and Planetary Science

### Keywords

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

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## Cite this

*Astrophysical Journal*,

*565*(1 II), L5-L8. https://doi.org/10.1086/339245