Constraints on the Alignment of Galaxies in Galaxy Clusters from $\sim$14,000 Spectroscopic Members

Understand

Torques acting on galaxies lead to physical alignments, but the resulting ellipticity correlations are difficult to predict.

• As they constitute a major contaminant for cosmic shear studies, it is important to constrain the intrinsic alignment signal observationally.
• We measured the alignments of satellite galaxies within 90 massive galaxy clusters in the redshift range 0.05<z<0.55 and quantified their impact on the cosmic shear signal.
• We combined a sample of 38,104 galaxies with spectroscopic redshifts with high-quality data from the Canada-France-Hawaii Telescope.