The dynamical state of eROSITA clusters and its impact on the brightest cluster galaxy luminosity

Context. The first Spectrum-Roentgen-Gamma (SRG) eROSITA public release contains 12 247 clusters and groups from its first 6 months of operation. We used the offset between the brightest cluster galaxy (BCG) and the X-ray peak ( D BCG − X ) to classify the cluster dynamical state of 3946 galaxy clusters and groups. Aims. We aim to investigate the evolution of the merger and relaxed cluster distributions with redshift and mass, and the distributions’ impact on the BCG. Methods. We used the X-ray peak from the eROSITA survey and the BCG position from the LS DR10 optical data, which includes the DECam eROSITA Survey optical data, to measure the D BCG − X offset. We modelled the distribution of D BCG − X , in units of R 500 , as the sum of two Rayleigh distributions representing the cluster’s relaxed and disturbed populations, and explored their evolution with redshift and mass. To explore the impact of the cluster’s dynamical state on the BCG luminosity, we separated the main sample according to the dynamical state. We defined clusters as relaxed if D BCG − X < 0.25 R 500 , disturbed if D BCG − X > 0.5 R 500 , and ‘diverse’ if 0.25 R 500 < D BCG − X < 0.5 R 500 . Results. We find no evolution of the merging fraction with redshift or mass. The width of the relaxed distribution increases with redshift, while the width of the two Rayleigh distributions decreases with mass. The analysis reveals that BCGs in relaxed clusters are brighter than BCGs in both the disturbed and diverse cluster populations. The most significant differences are found for high-mass clusters at higher redshifts. Conclusions. The results suggest that BCGs in low-mass clusters are less centrally bound than those in high-mass systems, irrespective of the dynamical state. Over time, BCGs in relaxed clusters progressively align with the potential centre. This alignment correlates with their luminosity growth relative to BCGs in dynamically disturbed clusters, underscoring the critical role of the cluster’s dynamical state in regulating BCG evolution.

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Publication Details

Journal
Astronomy and Astrophysics
Published
2025-05-06
DOI
https://doi.org/10.1051/0004-6361/202452440
Citations
8
Primary Topic
Galaxies: Formation, Evolution, Phenomena
Type
article
Field-Weighted Citation Impact
9.24

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article

The dynamical state of eROSITA clusters and its impact on the brightest cluster galaxy luminosity

Y. E. Bahar, Xiaoyuan Zhang, G. Damke, V. Ghirardini et al.
8 citations
Astronomy and Astrophysics
Galaxies: Formation, Evolution, Phenomena
9.24
article

The dynamical state of eROSITA clusters and its impact on the brightest cluster galaxy luminosity

Y. E. Bahar, Xiaoyuan Zhang, G. Damke, V. Ghirardini, S. Grandis, Rogério Monteiro-Oliveira, D. Hernández-Lang, E. Schlafly, J. Snigula, B. A. Weaver, P. Arévalo, M. Salvato, Johan Comparat, Matthias Kluge, Frank Balzer, Miguel Ramos, M. Landriau, F. Valdes, E. R. Carrasco, J. L. Nilo Castellón, M. Fabricius, E. Bulbul, J. J. Mohr, J. S. Sanders, A. Zenteno, A. Ramírez, Aihua Liu, Matthias Klein, A. Saro, H. Cuevas, Adam D. Myers, S. Véliz Astudillo, R. Kharkrang
article en
8 citations

Abstract

Context. The first Spectrum-Roentgen-Gamma (SRG) eROSITA public release contains 12 247 clusters and groups from its first 6 months of operation. We used the offset between the brightest cluster galaxy (BCG) and the X-ray peak ( D BCG − X ) to classify the cluster dynamical state of 3946 galaxy clusters and groups. Aims. We aim to investigate the evolution of the merger and relaxed cluster distributions with redshift and mass, and the distributions’ impact on the BCG. Methods. We used the X-ray peak from the eROSITA survey and the BCG position from the LS DR10 optical data, which includes the DECam eROSITA Survey optical data, to measure the D BCG − X offset. We modelled the distribution of D BCG − X , in units of R 500 , as the sum of two Rayleigh distributions representing the cluster’s relaxed and disturbed populations, and explored their evolution with redshift and mass. To explore the impact of the cluster’s dynamical state on the BCG luminosity, we separated the main sample according to the dynamical state. We defined clusters as relaxed if D BCG − X < 0.25 R 500 , disturbed if D BCG − X > 0.5 R 500 , and ‘diverse’ if 0.25 R 500 < D BCG − X < 0.5 R 500 . Results. We find no evolution of the merging fraction with redshift or mass. The width of the relaxed distribution increases with redshift, while the width of the two Rayleigh distributions decreases with mass. The analysis reveals that BCGs in relaxed clusters are brighter than BCGs in both the disturbed and diverse cluster populations. The most significant differences are found for high-mass clusters at higher redshifts. Conclusions. The results suggest that BCGs in low-mass clusters are less centrally bound than those in high-mass systems, irrespective of the dynamical state. Over time, BCGs in relaxed clusters progressively align with the potential centre. This alignment correlates with their luminosity growth relative to BCGs in dynamically disturbed clusters, underscoring the critical role of the cluster’s dynamical state in regulating BCG evolution.

Astronomy and AstrophysicsVol. 698
National Science Foundation, U.S. Department of Energy, National Aeronautics and Space Administration, University of Pennsylvania, Ohio State University, California Institute of Technology, University of Portsmouth, University College London, European Commission, University of Sussex, Deutsche Forschungsgemeinschaft, Eberhard Karls Universität Tübingen, Chinese Academy of Sciences, Ministério da Ciência, Tecnologia e Inovação, Conselho Nacional de Desenvolvimento Científico e Tecnológico, Max-Planck-Gesellschaft, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Financiadora de Estudos e Projetos, Universität Hamburg, Rheinische Friedrich-Wilhelms-Universität Bonn, Leibniz-Institut für Astrophysik Potsdam, Institut de Física d'Altes Energies, University of Illinois at Urbana-Champaign, Office of Science, Jet Propulsion Laboratory, Science and Technology Facilities Council, Leibniz-Gemeinschaft, Russian Academy of Sciences, Division of Astronomical Sciences, High Energy Physics, Integrated Electronics Engineering Center, Binghamton University, Argonne National Laboratory, Fermilab, Lawrence Berkeley National Laboratory, SLAC National Accelerator Laboratory
Openalex Percentile: Top 2%
Galaxies: Formation, Evolution, Phenomena
9.24
DOIOpen Access PDFOpenAlex
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