Dark Energy Survey Year 3 Results: Mis-centering calibration and X-ray-richness scaling relations in redMaPPer clusters

TL;DR

This study assesses the accuracy of the redMaPPer cluster finder in the Dark Energy Survey Year 3 data by analyzing mis-centering issues and establishing X-ray richness scaling relations, providing insights into cluster properties and calibration.

Contribution

It offers the first detailed analysis of mis-centering effects and X-ray richness scaling relations in DES Y3 clusters, improving cluster identification and characterization methods.

Findings

10-20% of clusters are miscentered with no dependence on richness or redshift.

The dominant miscentering causes include masking and bright neighboring galaxies.

X-ray temperature-richness relation has a scatter of 0.21 and varies modestly with redshift.

Abstract

We use Dark Energy Survey Year 3 (DES Y3) clusters with archival X-ray data from XMM-Newton and Chandra to assess the centering performance of the redMaPPer cluster finder and to measure key richness observable scaling relations. In terms of centering, we find that 10-20% of redMaPPer clusters are miscentered with no significant difference in bins of low versus high richness ($20<\lambda<40$ and $\lambda>40$) or redshift ($0.2<z<0.4$ and $0.4 <z < 0.65$). We also investigate the richness bias induced by miscentering. The dominant reasons for miscentering include masked or missing data and the presence of other bright galaxies in the cluster; for half of the miscentered clusters the correct central was one of the other possible centrals identified by redMaPPer, while for $\sim 40$% of miscentered clusters the correct central is not a redMaPPer member with most of these cases due to masking. In addition, we fit the scaling relations between X-ray temperature and richness and between X-ray luminosity and richness. We find a T$_X$-$\lambda$ scatter of $0.21 \pm 0.01$. While the scatter in T$_X$-$\lambda$ is consistent in bins of redshift, we do find modestly different slopes with high-redshift clusters displaying a somewhat shallower relation. Splitting based on richness, we find a marginally larger scatter for our lowest richness bin, $20 < \lambda < 40$. The X-ray properties of detected, serendipitous clusters are generally consistent with those for targeted clusters, but the depth of the X-ray data for undetected clusters is insufficient to judge whether they are X-ray underluminous in all but one case.