Cross-correlation weak lensing of sdss galaxy clusters. III. mass-to-light ratios

Erin S. Sheldon, David E. Johnston, Morad Masjedi, Timothy A. McKay, Michael R. Blanton, Ryan Scranton, Risa H. Wechsler, Benjamin P. Koester, Sarah M. Hansen, Joshua A. Frieman, James Annis

    Research output: Contribution to journalArticlepeer-review


    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 × 1012 h -1 M to clusters with M200 1015 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 r200, 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 Ωmb -2 M/L = 0.20±0.03, independent of the Hubble parameter.

    Original languageEnglish (US)
    Pages (from-to)2232-2248
    Number of pages17
    JournalAstrophysical Journal
    Issue number2
    StatePublished - 2009


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

    ASJC Scopus subject areas

    • Astronomy and Astrophysics
    • Space and Planetary Science


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