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Cross-correlation Weak Lensing of SDSS Galaxy Clusters III: Mass-to-light Ratio | | Erin S. Sheldon
; David E. Johnston
; Morad Masjedi
; Timothy A. McKay
; Michael R. Blanton
; Ryan Scranton
; Risa H. Wechsler
; Ben P. Koester
; Sarah M. Hansen
; Joshua A. Frieman
; James Anni
; | | Date: |
7 Sep 2007 | | Abstract: | We present measurements of the excess mass-to-light ratio (M/L) measured
around MaxBCG galaxy clusters observed in the SDSS. Using cross-correlation
weak lensing, we measure the excess mass density profile above the universal
mean Delta
ho(r) =
ho(r) - ar{
ho} for clusters in bins of richness and
optical luminosity. We also measure the excess ^{0.25}i-band luminosity density
Delta l(r) = l(r) - ar{l}. For both mass and light, we de-project the
profiles to produce 3D mass and light profiles over scales from 25 kpc/h to 22
Mpc/h. From these profiles we calculate the cumulative excess mass Delta M(r)
and excess light Delta L(r) as a function of separation from the BCG. On small
scales, where
ho(r) >> ar{
ho}, the integrated M/L profile may be
interpreted as the cluster M/L. We find the (Delta M/Delta L)_{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
ho(r) << ar{
ho}, the Delta M/Delta L approaches
an asymptotic value independent of scale or cluster richness. For small groups,
the mean (Delta M/Delta L)_{200} is much smaller than the asymptotic value,
while for large clusters it 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_{ml} = 362+/-54 h measured in the ^{0.25}i-bandpass. The
parameter b_{ml} 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 Omega_m/b^2_{ml} =
0.20+/-0.03, independent of the Hubble parameter. | | Source: | arXiv, 0709.1162 | | Services: | Forum | Review | PDF | Favorites | |
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