Weak and Not So Weak Lensing: Shear Calibration and Dark Matter Structure in Galaxy Clusters

Abstract

In the last two decades, wide and deep astronomical surveys have been conducted and lead to productive observations. Built on the experience of these past and ongoing surveys, Rubin Observatory will carry out the Legacy Survey of Space and Time (LSST) to address broad scientific goals and open new windows on the Universe in the next decade. As a precursor task for LSST, we conduct gravitational lensing analysis on both simulated and real-world imaging data with algorithms and software frameworks of LSST. We introduce the image simulation pipeline, jedisim, of galaxy cluster lensing with realistic galaxy images cut from Hubble Space Telescope (HST). The simulations represent realistic galaxy distributions and morphologies, and simulate lensing effects via a ray-tracing algorithm. The simulated images are processed and measured by the LSST Data Management (DM) pipeline. By comparing the measured reduced shear g_meas and the true reduced shear g_true, we observe non-linearity up to g~0.6. We fit polynomials to the data with quadratic correction adequate to g~0.4. This study yields a first relationship between reality and shape measurement of LSST DM pipeline, and serves as the first step of the overall goal of mass calibration in clusters. In addition, we select and observe a massive, low-redshift galaxy cluster, Abell 3628, with Dark Energy Camera (DECam). LSST DM pipeline is applied to measure lensing signals and plot mass distribution. This study provides a first map of dark matter structure in A3628, and will be a low-redshift anchor for the upcoming LSST deep survey data.