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X-ray study of the dynamical properties of photometrically selected galaxy clusters

Grant number: 18/09592-1
Support type:Scholarships abroad - Research Internship - Master's degree
Effective date (Start): September 03, 2018
Effective date (End): March 02, 2019
Field of knowledge:Physical Sciences and Mathematics - Astronomy - Extragalactic Astrophysics
Principal Investigator:Gastão Cesar Bierrenbach Lima Neto
Grantee:Johnny Hebert Esteves de Queiroz
Supervisor abroad: Marcelle Soares dos Santos
Home Institution: Instituto de Astronomia, Geofísica e Ciências Atmosféricas (IAG). Universidade de São Paulo (USP). São Paulo , SP, Brazil
Local de pesquisa : Brandeis University, United States  
Associated to the scholarship:16/25599-0 - The AGN-cluster connection: an optical and X-ray view, BP.MS


The mass and redshift distribution of galaxy clusters are key observables to determine the parameters of the cosmological model of the universe. The great challenge, however, is the efficient selection and precise determination of the masses of these objects. Samples selected based only on photometric data are subject to various complications such as projection effects, fragmentation due to sub-structures, and confusion in the determination of the central galaxy. Accurate determination of the central galaxy, in particular, is key to the determination of the cluster masses. The redMaPPer algorithm is an optimized cluster finder used by large photometric surveys such as the Dark Energy Survey (DES), the Sloan Digital Sky Survey (SDSS) and the Large Synoptic Survey Telescope (LSST). It is estimated that approximately 20% of the objects identified by redMaPPer are miscentered (i.e. the optical center is not the same as the X-ray center).This project aims to quantify the relationship between the astrophysical properties and the probability of error in determining the center of redMaPPer clusters. Specifically, we will study DES and SDSS samples for which X-ray data are in the Chandra archive, which allows us to characterize their dynamical state. As dynamical perturbations caused by mergers between clusters are thought to be one of the main causes of miscentering, we expect results of this study to enable the development of new methods of mitigaion of the miscentering issue in photometrically selected cluster samples. (AU)