AR-2019-2020

that require intracluster processes from those that do not. Comparing the simulation results with measurements of real cluster galaxies, the research work presented evidence that the kinematics of red (quiescent) satellite galaxies are consistent with earlier infall times than that of blue (star- forming) satellites. Cosmological constraints from cosmic shear two-point correlation func- tions with HSC survey first-year data The gravitational lensing effect in the Einstein’s general theory of relativity causes the shapes of background galaxies to get distorted due to the gravitational field of the intervening large scale structure. By measuring the exquisite images of about 9 million galaxies taken with the Subaru telescope using the Hyper Suprime-Cam (HSC) camera, the survey collaboration measured the weak lensing effect. The cosmic weak lensing shear two-point correlation functions were measured using data from the HSC survey first-year shear catalogue covering 137 sq deg of the sky. This study complemented the study performed the year before using power spectrum methods. For a flat lambda-dominated cold dark matter model, the collaborators which included Surhud More , were able to constrain the amplitude of density fluctuations with an accuracy of 3.5 percent similar to that in the study using power spectrum methods. In comparison with Planck cosmic microwave background constraints, these results prefer slightly lower values of these amplitude of density fluctuations, although metrics such as the Bayesian evidence ratio test do not show significant evidence for discordance between these results. The ongoing full HSC survey data will contain several times more area, and will lead to significantly improved cosmological constraints. SuGOHI-VI. Crowdsourced lens finding with Space Warps The lens search was carried out, targeting massive galaxies, selected from over 442 square degrees of photometric data of the Hyper Suprime-Cam (HSC) survey using Space Warps, a citizen science project. Nearly 6,000 citizen volunteers participated in the experiment to inspect a sample of 300,000 galaxies. In parallel, Anupreeta More and collaborators used YattaLens, an automated lens finding algorithm, to look for lenses in the same sample of galaxies. Based on a statistical analysis of classification data from the volunteers and combined with lenses from YattaLens, they were able to find 14 definite lenses, 129 probable lenses, and 581 possible lenses. YattaLens found half the number of lenses discovered via crowdsourcing which is able to produce samples of lens candidates with high completeness and purity, compared to currently available automated algorithms. A hybrid approach, in which the visual inspection of samples of lens candidates pre-selected by discovery algorithms and/or coupled to machine learning is crowdsourced, will be a viable option for lens finding in the 2020s. SuGOHI-V. Group-to-cluster scale lens search from the HSC-SSP survey The largest sample of candidate strong gravitational lenses belonging to the survey of gravitation- ally lensed objects in Hyper Suprime-Cam Imaging for group-to-cluster scale (SuGOHI-c) systems are reported. Anupreeta More and collaborators visually inspected ∼ 39,500 galaxy clusters, selected from several catalogues spanning the cluster redshift range 0 . 05 < zcl < 1 . 38 . Over 640 candidate lens systems were discovered, of which 536 were new. From the full sample, 47 are almost certainly bonafide lenses, 181 of them are highly probable lenses, and 413 are possible lens systems. Additionally, 131 galaxy-scale lens candidates were serendipitously discovered during the inspection. Eight systems were spectroscopically confirmed as strong gravitational lenses. Since the HSC-SSP is an ongoing survey, it is expected to find ∼ 600 definite or probable lenses using this procedure and even more if combined with other lens finding methods.