We present measurements of the extended dark halo profiles of bright early type galaxies at redshifts 0.1 < z < 0.9 obtained via galaxy-galaxy lensing analysis of images taken at the CFHT using the UH8K CCD mosaic camera .
Six 0 ^ { \circ } 5 \times 0 ^ { \circ } 5 fields were observed for a total of 2 hours each in I and V , resulting in catalogs containing \sim 20000 galaxies per field .
We used V - I color and I magnitude to select bright early type galaxies as the lens galaxies , yielding a sample of massive lenses with fairly well determined redshifts and absolute magnitudes M \sim M _ { * } \pm 1 .
We paired these with faint galaxies lying at angular distances 20 \arcsec < \theta < 60 \arcsec , corresponding to physical radii of 26 < r < 77 ~ { } { h } ^ { -1 } { kpc } ( z = 0.1 ) and 105 < r < 315 ~ { } { h } ^ { -1 } { kpc } ( z = 0.9 ) , and computed the mean tangential shear \gamma _ { T } ( \theta ) of the faint galaxies .
The shear falls off with radius roughly as \gamma _ { T } \propto 1 / \theta as expected for flat rotation curve halos .
The shear values were weighted in proportion to the square root of the luminosity of the lens galaxy .
This is optimal if the halo mass at a given radius varies as M \propto \sqrt { L } , as is the case at smaller radii , and in this context our results give a value for the average mean rotation velocity of an L _ { \star } galaxy halo at r \sim 50 - 200 ~ { } { h } ^ { -1 } { kpc } of v _ { \star } = 238 ^ { +27 } _ { -30 } ~ { } { km sec } ^ { -1 } for a flat lambda ( \Omega _ { { m } 0 } = 0.3 , \Omega _ { \lambda 0 } = 0.7 ) cosmology ( v _ { \star } = 269 ^ { +34 } _ { -39 } ~ { } { km sec } ^ { -1 } for Einstein-de Sitter ) , and with little evidence for evolution with redshift .
These halo masses are somewhat ( 2 - 3 times ) lower than a simple perfectly flat rotation curve extrapolation from smaller-scale dynamical measurements .
They are also considerably lower than the masses of halos found from the best studied X-ray halos .
They do however agree extremely well with the masses of halos of the same abundance in lambda-CDM simulations .
We find a mass-to-light ratio of M / L _ { B } \simeq 121 \pm 28 h ( r / 100 ~ { } { h } ^ { -1 } { kpc } ) ( for L _ { \star } galaxies ) and these halos constitute \Omega \simeq 0.04 \pm 0.01 ( r / 100 ~ { } { h } ^ { -1 } { kpc } ) of closure density .