Bias-hardened CMB lensing

Abstract

We present new methods for lensing reconstruction from CMB temperature\nfluctuations which have smaller mean-field and reconstruction noise bias\ncorrections than current lensing estimators, with minimal loss of\nsignal-to-noise. These biases are usually corrected using Monte Carlo\nsimulations, and to the extent that these simulations do not perfectly mimic\nthe underlying sky there are uncertainties in the bias corrections. The\nbias-hardened estimators which we present can have reduced sensitivity to such\nuncertainties, and provide a desirable cross-check on standard results. To test\nour approach, we also show the results of lensing reconstruction from simulated\ntemperature maps given on 100 deg^2, and confirm that our approach works well\nto reduce biases for a typical masked map in which 70 square masks each having\n10 arcminute on a side exist, covering 2% of the simulated map, which is\nsimilar to the masks used in the current SPT lensing analysis.\n