# A Method for Weak Lensing Flexion Analysis by the HOLICs Moment Approach - Astrophysics

Abstract: We have developed a method for measuring higher-order weak lensingdistortions of faint background galaxies, namely the weak gravitationalflexion, by fully extending the Kaiser, Squires and Broadhurst method to includehigher-order lensing image characteristics HOLICs introduced by Okura,Umetsu, and Futamase. We take into account explicitly the weight function incalculations of noisy shape moments and the effect of higher-order PSFanisotropy, as well as isotropic PSF smearing. Our HOLICs formalism allowsaccurate measurements of flexion from practical observational data in thepresence of non-circular, anisotropic PSF. We test our method using mockobservations of simulated galaxy images and actual, ground-basedSubaru observations of the massive galaxy cluster A1689 $z=0.183$. From thehigh-precision measurements of spin-1 first flexion, we obtain ahigh-resolution mass map in the central region of A1689. The reconstructed massmap shows a bimodal feature in the central $4-\times 4-$ region of the cluster.The major, pronounced peak is associated with the brightest cluster galaxy andcentral cluster members, while the secondary mass peak is associated with alocal concentration of bright galaxies. The refined, high-resolution mass mapof A1689 demonstrates the power of the generalized weak lensing analysistechniques for quantitative and accurate measurements of the weak gravitationallensing signal.

Author: Yuki Okura 1, Keiichi Umetsu 2, Toshifumi Futamase 1 1 Tohoku University, 2 ASIAA

Source: https://arxiv.org/