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 ∼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 (mK arcmin). Subject headings: cosmic microwave background — dark matter — large-scale structure of universe