The X-CLASS survey: A catalogue of 1646 X-ray-selected galaxy clusters up to z ∼ 1.5

Abstract

Context. Cosmological probes based on galaxy clusters rely on cluster number counts and large-scale structure information. X-ray cluster surveys are well suited for this purpose because they are far less affected by projection effects than optical surveys, and cluster properties can be predicted with good accuracy. Aims. The XMM Cluster Archive Super Survey, X-CLASS, is a serendipitous search of X-ray-detected galaxy clusters in 4176 XMM-Newton archival observations until August 2015. All observations are clipped to exposure times of 10 and 20 ks to obtain uniformity, and they span ∼269 deg 2 across the high-Galactic latitude sky (|b| > 20 o ). The main goal of the survey is the compilation of a wellselected cluster sample suitable for cosmological analyses. Methods. We describe the detection algorithm, the visual inspection, the verification process, and the redshift validation of the cluster sample, as well as the cluster selection function computed by simulations. We also present the various metadata that are released with the catalogue, along with two different count-rate measurements, an automatic one provided by the pipeline, and a more detailed and accurate interactive measurement. Furthermore, we provide the redshifts of 124 clusters obtained with a dedicated multi-object spectroscopic follow-up programme. Results. With this publication, we release the new X-CLASS catalogue of 1646 well-selected X-ray-detected clusters over a wide sky area, along with their selection function. The sample spans a wide redshift range, from the local Universe up to z ∼ 1.5, with 982 spectroscopically confirmed clusters, and over 70 clusters above z = 0.8. The redshift distribution peaks at z∼ 0.1, while if we remove the pointed observations it peaks at z ∼ 0.3. Because of its homogeneous selection and thorough verification, the cluster sample can be used for cosmological analyses, but also as a test-bed for the upcoming eROSITA observations and other current and future large-area cluster surveys. It is the first time that such a catalogue is made available to the community via an interactive database which gives access to a wealth of supplementary information, images, and data.

Catalog of X-ray-selected extended galaxy clusters from the ROSAT All-Sky Survey (RXGCC)

“…In addition to ROSAT, the XMM-Newton and Chandra observatories are also widely used to identify galaxy clusters. With improved resolution and sensitivity, as well as longer exposure times, they could identify faint clusters at high redshift, as shown, for instance, in the works of Mehrtens et al (2012), Clerc et al (2012Clerc et al ( , 2016, Takey et al (2011Takey et al ( , 2013Takey et al ( , 2014Takey et al ( , 2016, Pacaud et al (2016), Koulouridis et al (2021).…”

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

“…As eFEDS and the XXL surv e y were taken in different parts of the sky there are no clusters in common. Although we note that the X-CLASS analysis of the XMM archive (up to 2015 August) that made use of the XXL pipelines does contain some eFEDS candidates (Koulouridis et al 2021 ). Comparisons are limited to ensemble distributions of the cluster samples.…”

Dynamical state of galaxy clusters evaluated from X-ray images

“…Second, we combined several large cluster catalogues (Abell et al 1989;Piffaretti et al 2011;Rykoff et al 2014;Wen et al 2012;Wen et al 2018;Zou et al 2021;Koulouridis et al 2021), and check if any clusters serendipitously observed in XMM-Newton observations in the released dataset. The instrument mode for the MOS1 and MOS2 is set as "FULL FRAME", and the modes "FULL FRAME", "EXTENDED FULL FRAME" and "LARGE WINDOW" are chosen for the EPN sytem.…”