Measurement of a Cosmographic Distance Ratio with Galaxy and CMB Lensing

Understand

We measure the gravitational lensing shear signal around dark matter halos hosting CMASS galaxies using light sources at $z\sim 1$ (background galaxies) and at the surface of last scattering at $z\sim 1100$ (the cosmic microwave background).

• The galaxy shear measurement uses data from the CFHTLenS survey, and the microwave background shear measurement uses data from the {\it Planck} satellite.
• The ratio of shears from these cross-correlations provides a purely geometric distance measurement across the longest possible cosmological lever arm.
• This is because the matter distribution around the halos, including uncertainties in galaxy bias and systematic errors such as miscentering, cancels in the ratio for halos in thin redshift slices.