Ellipticities of Galaxy Cluster Halos from Halo–Shear–Shear Correlations

Abstract

We report the first detection of the halo ellipticities of galaxy clusters by applying the halo–shear–shear correlations (HSSCs), without the necessity of using major axis determination. We use the Fourier_Quad shear catalog based on the Hyper Suprime-Cam Survey and the group catalog from the Dark Energy Spectroscopic Instrument Legacy Surveys for the measurement of group/cluster lensing and HSSC. Our analysis includes off-centering effects. We obtain the average projected ellipticity of dark matter halos with mass $13.5\lt {\rm{log}}({M}_{G}h/{M}_{\odot })\lt 14.5$ within a 1.3 virial radius to be $0.4{8}_{-0.19}^{+0.12}$ . We divide the sample into two groups based on mass and redshift, and we find that halos with higher mass tend to exhibit increased ellipticity. We also reveal that high-richness halos have larger ellipticities, confirming the physical picture from numerical simulation that high-richness halos have a dynamical youth and more active mass accretion phase.

Keywords

• Weak gravitational lensing
• Galaxy dark matter halos
• Gravitational lensing shear