Galaxy clusters are the largest gravitationally collapsed structures in the Universe. X-ray observations of clusters provide information on dark matter and the structure formation in the Universe over cosmological time. This can be used to constrain cosmological parameters that are complementary to other cosmological probes. Taking advantage of the potential galaxy clusters have, in combination with the most recent astronomical surveys for cluster finding, allows us to produce leading constraints on cosmological models.
The XCSDR2-DESY3 cluster catalogue, a subset of the XMM Cluster Survey (XCS) Data Release 2 within the Dark Energy Survey (DES) Year 3 footprint, constitutes approximately 722 optically-confirmed clusters. Most of these clusters have associated spectroscopic or photometric redshifts, reliable X-ray bolometric luminosities, and X-ray temperatures. The catalogue is split into samples for different research areas; e.g. high redshift clusters for galaxy evolution; clusters with spectroscopic redshifts for scaling relations and cosmology; and high temperature clusters for combined multi-wavelength studies. The aim of building this sample is to lay the groundwork for the next generation of wide-area and deep joint optical and X-ray galaxy cluster datasets.
Since gravity has a central role in galaxy cluster formation, clusters act as astrophysical laboratories to test modified theories of gravity models in the outskirts of galaxy clusters. By comparing X-ray and weak lensing profiles, it is possible to put constrains on such models, particularly those which rely on screening mechanisms or those that postulate an emergent gravity in the outskirts of clusters to substitute dark matter. By combining detected X-ray clusters with weak lensing data from DES,we were able to place constraints on these type of models. The results are found to be consistent with general relativity,i.e. they do not require gravity to be modified, and are in the same level of confidence as previous studies
