Dark energy survey year 3 results: Mis-centering calibration and X-ray-richness scaling relations in redMaPPer clusters

We use Dark Energy Survey Year 3 (DES Y3) clusters with archival XMM-Newton and Chandra X-ray data to assess the centering performance of the redMaPPer cluster finder and to measure key richness observable scaling relations. We find that 10-20% of redMaPPer clusters are miscentered, both when comparing to the X-ray peak position and to the visually identified central cluster galaxy. We find no significant difference in miscentering in bins of low versus high richness or redshift. 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 possible centrals identified by redMaPPer, while for ∼40% of miscentered clusters the correct central is not a redMaPPer member mostly due to masking. Additionally, we fit scaling relations of X-ray temperature and luminosity with richness. We find a TX-λ scatter of 0.21 ± 0.01. While the scatter in TX-λ is consistent in redshift bins, we 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 75 we detect nearly all of the clusters falling within existing X-ray pointings. The X-ray properties of detected, serendipitous clusters are generally consistent with those of targeted clusters.</p

The XMM Cluster Survey: an independent demonstration of the fidelity of the eFEDS galaxy cluster data products and implications for future studies

We present the first comparison between properties of clusters of galaxies detected by the eROSITA Final Equatorial-Depth Survey (eFEDS) and the XMM Cluster Survey (XCS). We have compared, in an ensemble fashion, properties from the eFEDS X-ray cluster catalogue with those from the Ultimate XMM eXtragaLactic (XXL) survey project (XXL-100-GC). We find the redshift and temperature (TX) distributions to be similar, with a larger proportion of clusters above 4 keV in the XXL-100-GC sample; fractional temperature uncertainties are significantly larger in eFEDS compared to XXL. We find 62 eFEDS cluster candidates with XMM data (eFEDS-XMM sample); 10 do not have good enough XMM data to confirm or deny, 11 are classed as sample contaminants, and 4 have their X-ray flux contaminated by another source. The majority of eFEDS-XMM sources have longer XMM exposures than eFEDS, and most eFEDS positions are within 100 kpc of XCS positions. Our eFEDS-XCS sample of 37 clusters is used to calculate minimum sample contamination fractions of ∼18 and ∼9 per cent in the eFEDS X-ray and optically confirmed samples, respectively, in general agreement with eFEDS findings. We directly compare 29 X-ray luminosities (LX) measured by eFEDS and XCS, finding excellent agreement. Eight clusters have a TX measured by XCS and eFEDS, and we find that XMM temperatures are 25 ± 9 per cent larger than their eROSITA counterparts. Finally, we construct LX-TX scaling relations based on eFEDS and XCS measurements, which are in tension; the tension is decreased when we measure a third scaling relation with calibrated XCS temperatures

The XMM cluster survey: exploring scaling relations and completeness of the dark energy survey year 3 redMaPPer cluster catalogue

We cross-match and compare characteristics of galaxy clusters identified in observations from two sky surveys using two completely different techniques. One sample is optically selected from the analysis of 3 years of Dark Energy Survey observations using the redMaPPer cluster detection algorithm. The second is X-ray selected from XMM observations analysed by the XMM Cluster Survey. The samples comprise a total area of 57.4 deg2, bounded by the area of four contiguous XMM survey regions that overlap the DES footprint. We find that the X-ray-selected sample is fully matched with entries in the redMaPPer catalogue, above λ > 20 and within 0.1 z LX –TX ), luminosity–richness (LX –λ), and temperature–richness (TX –λ) scaling relations. We find that the fitted forms of the LX –TX relations are consistent between the two selection methods and also with other studies in the literature. However, we find tentative evidence for a steepening of the slope of the relation for low richness systems in the X-ray-selected sample. When considering the scaling of richness with X-ray properties, we again find consistency in the relations (i.e. LX –λ and TX –λ) between the optical and X-ray-selected samples. This is contrary to previous similar works that find a significant increase in the scatter of the luminosity scaling relation for X-ray-selected samples compared to optically selected samples.</p