Satellite content and halo mass of galaxy clusters: comparison between red-sequence and halo-based optical cluster finders

Abstract

ABSTRACT Cluster cosmology depends critically on how optical clusters are selected from imaging surveys. We compare the conditional luminosity function (CLF) and weak-lensing (WL) halo masses between two different cluster samples at fixed richness, detected within the same volume (0.1 < z < 0.34) using the red-sequence and halo-based methods. After calibrating our CLF deprojection method against mock galaxy samples, we measure the 3D CLFs by cross-correlating clusters with Sloan Digital Sky Survey photometric galaxies. As expected, the CLFs of red-sequence and halo-based finders exhibit redder and bluer populations, respectively. The red-sequence clusters have a flat distribution of red galaxies at the faint end, while the halo-based clusters host a decreasing faint red and a boosted blue population at the bright end. By comparing subsamples of clusters that have a match between the two catalogues to those without matches, we discover that the CLF shape is mainly caused by the different cluster centroiding. However, the average WL halo mass between the matched and non-matched clusters is consistent with each other in either cluster sample for halos with λ > 30 ($M_{h}^{\mathrm{WL}}\gt 1.5\times 10^{14}h^{-1}{\rm M}_{\odot }$). Since the colour preferences of the two cluster finders are almost orthogonal, such a consistency indicates that the scatter in the mass–richness relation of either cluster sample is close to random. Therefore, while the choice of how optical clusters are identified impacts the satellite content, our result suggests that it should not introduce strong systematic biases in cluster cosmology, except for the λ < 30 regime.