We use weak gravitational lensing to measure the masses of five galaxy clusters selected from the South Pole Telescope ( SPT ) survey , with the primary goal of comparing these with the SPT Sunyaev–Zel ’ dovich ( SZ ) and X-ray based mass estimates .
The clusters span redshifts 0.28 < z < 0.43 and have masses M _ { 500 } > 2 \times 10 ^ { 14 } h ^ { -1 } M _ { \odot } , and three of the five clusters were discovered by the SPT survey .
We observed the clusters in the g ^ { \prime } r ^ { \prime } i ^ { \prime } passbands with the Megacam imager on the Magellan Clay 6.5m telescope .
We measure a mean ratio of weak lensing ( WL ) aperture masses to inferred aperture masses from the SZ data , both within an aperture of R _ { 500 , \mathrm { SZ } } derived from the SZ mass , of 1.04 \pm 0.18 .
We measure a mean ratio of spherical WL masses evaluated at R _ { 500 , \mathrm { SZ } } to spherical SZ masses of 1.07 \pm 0.18 , and a mean ratio of spherical WL masses evaluated at R _ { 500 , \mathrm { WL } } to spherical SZ masses of 1.10 \pm 0.24 .
We explore potential sources of systematic error in the mass comparisons and conclude that all are subdominant to the statistical uncertainty , with dominant terms being cluster concentration uncertainty and N -body simulation calibration bias .
Expanding the sample of SPT clusters with WL observations has the potential to significantly improve the SPT cluster mass calibration and the resulting cosmological constraints from the SPT cluster survey .
These are the first WL detections using Megacam on the Magellan Clay telescope .