Abstract

I will report on the first detection of lensing of the cosmic microwave background (CMB) by dark matter halos. Halo lensing of the CMB provides a method for constraining cluster masses complementary to optical weak lensing, with the advantage that the source plane has a very well determined redshift and statistical properties. In this work, the lensing field was reconstructed from CMB temperature observations using the ACT Pol telescope and stacked at the location of CMASS galaxies which trace dark matter halos of _{10^13 M_solar galaxy groups, providing a 3.2 sigma detection and a} 35% mass constraint. I will summarize measurements by Planck and SPT that followed this detection and describe how contamination from the thermal Sunyaev-⁠Zeldovich effect can be dealt with when using this method to calibrate cluster masses with ongoing and future high-⁠resolution CMB experiments.