## Abstract

We present measurements of the excess mass-to-light ratio (M/L) measured around MaxBCG galaxy clusters observed in the Sloan Digital Sky Survey. This red-sequence cluster sample includes objects from small groups with M _{200} 5 × 10^{12} h ^{-1} M_{⊙} to clusters with M_{200} 10^{15} h^{-1} M_{⊙}. Using cross-correlation weak lensing, we measure the excess mass density profile above the universal mean Δρ(r) = ρ(r)-ρ̄ for clusters in bins of richness and optical luminosity. We also measure the excess luminosity density Δℓ(r) = ℓ(r)-ℓ̄ measured in the z = 0.25 i band. For both mass and light, we de-project the profiles to produce three-dimensional mass and light profiles over scales from 25 h ^{-1} kpc to 22 h ^{-1} Mpc. From these profiles we calculate the cumulative excess mass ΔM(r) and excess light ΔL(r) as a function of separation from the BCG. On small scales, where , the integrated mass-to-light profile (ΔM/ΔL)(r) may be interpreted as the cluster M/L. We find the (ΔM/ΔL)_{200}, the M/L within r_{200}, scales with cluster mass as a power law with index 0.33±0.02. On large scales, where ρ(r)∼ ρ̄, the ΔM/ΔL approaches an asymptotic value independent of cluster richness. For small groups, the mean (ΔM/ΔL) _{200} is much smaller than the asymptotic value, while for large clusters (ΔM/ΔL)_{200} is consistent with the asymptotic value. This asymptotic value should be proportional to the mean M/L of the universe 〈M/L〉. We find 〈M/L〉b^{-2} _{M/L} = 362 54h (statistical). There is additional uncertainty in the overall calibration at the 10% level. The parameter b ^{2} _{M/L} is primarily a function of the bias of the L ≲ L _{*} galaxies used as light tracers, and should be of order unity. Multiplying by the luminosity density in the same bandpass we find Ω_{m}b ^{-2} _{M/L} = 0.20±0.03, independent of the Hubble parameter.

Original language | English (US) |
---|---|

Pages (from-to) | 2232-2248 |

Number of pages | 17 |

Journal | Astrophysical Journal |

Volume | 703 |

Issue number | 2 |

DOIs | |

State | Published - 2009 |

## Keywords

- Dark matter
- Galaxies: clusters: general
- Gravitational lensing
- Large-scale structure of universe

## ASJC Scopus subject areas

- Astronomy and Astrophysics
- Space and Planetary Science