Mapping the dark matter through the cosmic microwave background damping tail

The lensing of cosmic microwave background (CMB) photons by intervening large-scale structure leaves a characteristic imprint on its arcminute-scale anisotropy that can be used to map the dark matter distribution in projection on degree scales or similar to 100 h(-1) Mpc comoving. We introduce a new algorithm for mass reconstruction that optimally utilizes information from the weak lensing of CMB anisotropies in the damping tail. Individual degree-scale mass structures can be recovered with a high signal-to-noise ratio from a foreground-free CMB map of arcminute-scale resolution, specifically with an FWHM beam less than 5' and a noise level less than 15 (10(-6) arcmin) or 41 (muK arcmin).