Optical galaxy cluster mock catalogs with realistic projection effects: Validations with the SDSS clusters

Understand

Galaxy clusters identified in optical imaging surveys suffer from projection effects: Physically unassociated galaxies along a cluster's line of sight can be counted as its members and boost the observed richness (the number of cluster members).

• To model the impact of projection on cluster cosmology analyses, we apply a halo occupation distribution model to N-body simulations to simulate the red galaxies contributing to cluster members, and we use the number of galaxies in a cylinder along the line of sight (counts in cylinders) to model the impact of projection on cluster richness.
• We compare three projection models: uniform, quadratic, and Gaussian, and we convert between them by matching their effective cylinder volumes.
• We validate our mock catalogs using SDSS redMaPPer clusters' data vectors, including counts vs.