Mass and Light in the Universe

Abstract

We present a weak lensing and photometric study of six 05 × 05 fields observed at the Canada-France-Hawaii Telescope using the UH8K CCD mosaic camera. The fields were observed for a total of 2 hr each in I and V, resulting in catalogs containing ~20,000 galaxies per passband per field. We use V-I color and I magnitude to select bright early-type galaxies at redshifts 0.1 < z < 0.9. We measure the gravitational shear from faint galaxies in the range 21 < mI < 25 from a composite catalog and find a strong correlation with that predicted from the early types if they trace the mass with M/LB 300 ± 75 h M☉/L☉ for a flat (Ωm0 = 0.3,Ωλ0 = 0.7) lambda cosmology and M/LB 400 ± 100 h M☉/L☉ for Einstein-de Sitter. We make two-dimensional reconstructions of the mass surface density. Cross-correlation of the measured mass surface density with that predicted from the early-type galaxy distribution shows a strong peak at zero lag (significant at the 5.2 σ level). We azimuthally average the cross-correlation and autocorrelation functions. We conclude that the profiles are consistent with early-type galaxies tracing mass on scales of ≥45'' (≥200 h-1 kpc at z = 0.5). We subdivide our bright early-type galaxies by redshift and obtain similar conclusions. These M/LB ratios imply Ωm0 0.10 ± 0.02 (Ωm0 0.13 ± 0.03 for Einstein-de Sitter) of closure density.