Subaru weak lensing measurement of a z = 0.81 cluster discovered by the Atacama Cosmology Telescope Survey

We present a Subaru weak lensing measurement of ACT-CL J0022.2 0036, one of the most luminous, high-redshift (z = 0.81) Sunyaev-Zel’dovich (SZ) clusters discovered in the 268 deg 2 equatorial region survey of the Atacama Cosmology Telescope that overlaps with SDSS Stripe 82 field. Ours is the first weak lensing study with Subar u at such high redshifts. For the weak lensing analysis using i ′ -band images, we use a model-fitting (Gauss-Laguerre shapel et) method to measure shapes of galaxy images, where we fit galaxy images in different exposures simultaneously to obtain best-fit ellipticities ta king into account the different PSFs in each exposure. We also take into account the astrometric distortion effect on galaxy images by performing the model fitting in the world coordinate s ystem. To select background galaxies behind the cluster at z = 0.81, we use photometric redshift (photo-z) estimates �