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Published April 2025 | Version Published
Journal Article Open

The hierarchical growth of bright central galaxies and intracluster light as traced by the magnitude gap

Creators

  • 1. ROR icon University of Nottingham
  • 2. ROR icon NOIRLab
  • 3. ROR icon National Observatory
  • 4. ROR icon Fermilab
  • 5. ROR icon Universität Hamburg
  • 6. ROR icon University of the Witwatersrand
  • 7. ROR icon University of KwaZulu-Natal
  • 8. ROR icon Laboratório Interinstitucional de e-Astronomia
  • 9. ROR icon University of Michigan–Ann Arbor
  • 10. ROR icon University of Portsmouth
  • 11. ROR icon University College London
  • 12. ROR icon Instituto de Astrofísica de Canarias
  • 13. ROR icon Institute for High Energy Physics
  • 14. ROR icon Durham University
  • 15. ROR icon Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas
  • 16. ROR icon Indian Institute of Technology Hyderabad
  • 17. ROR icon California Institute of Technology
  • 18. ROR icon University of Oslo
  • 19. ROR icon University of Chicago
  • 20. ROR icon Institute for Theoretical Physics
  • 21. ROR icon University of Pennsylvania
  • 22. ROR icon Ludwig-Maximilians-Universität München
  • 23. ROR icon National Center for Supercomputing Applications
  • 24. ROR icon University of Illinois Urbana-Champaign
  • 25. ROR icon University of Queensland
  • 26. ROR icon University of California, Santa Cruz
  • 27. ROR icon The Ohio State University
  • 28. ROR icon Harvard-Smithsonian Center for Astrophysics
  • 29. ROR icon Macquarie University
  • 30. ROR icon Lowell Observatory
  • 31. ROR icon Jet Propulsion Lab
  • 32. ROR icon Laboratory of Subatomic Physics and Cosmology
  • 33. ROR icon Institució Catalana de Recerca i Estudis Avançats
  • 34. ROR icon Carnegie Mellon University
  • 35. ROR icon Stanford University
  • 36. ROR icon SLAC National Accelerator Laboratory
  • 37. ROR icon Northeastern University
  • 38. ROR icon Lancaster University
  • 39. ROR icon Oak Ridge National Laboratory
  • 40. ROR icon Argonne National Laboratory
  • 41. ROR icon Cerro Tololo Inter-American Observatory
  • 42. ROR icon University of California, Berkeley
  • 43. ROR icon Lawrence Berkeley National Laboratory
  • 44. ROR icon University of Southampton

Abstract

Using a sample of 2800 galaxy clusters identified in the Dark Energy Survey across the redshift range ⁠0.20 < z < 0.60, we characterize the hierarchical assembly of bright central galaxies (BCGs) and the surrounding intracluster light (ICL). To quantify hierarchical formation we use the stellar mass–halo mass (SMHM) relation, comparing the halo mass, estimated via the mass–richness relation, to the stellar mass within the BCG + ICL system. Moreover, we incorporate the magnitude gap (M14), the difference in brightness between the BCG (measured within 30 kpc) and fourth brightest cluster member galaxy within 0.5 ⁠R₂₀₀,c, as a third parameter in this linear relation. The inclusion of M14, which traces BCG hierarchical growth, increases the slope and decreases the intrinsic scatter, highlighting that it is a latent variable within the BCG + ICL SMHM relation. Moreover, the correlation with M14 decreases at large radii. However, the stellar light within the BCG + ICL transition region (30 –80 kpc) most strongly correlates with halo mass and has a statistically significant correlation with M14. Since the transition region and M14 are independent measurements, the transition region may grow due to the BCG’s hierarchical formation. Additionally, as M14 and ICL result from hierarchical growth, we use a stacked sample and find that clusters with large M14 values are characterized by larger ICL and BCG + ICL fractions, which illustrates that the merger processes that build the BCG stellar mass also grow the ICL. Furthermore, this may suggest that M14 combined with the ICL fraction can identify dynamically relaxed clusters.

Copyright and License

© 2025 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.

Acknowledgement

JBGM would like to thank the anonymous referee for all of their help and feedback, which significantly strengthened this manuscript. JBGM would like to thank Nina Hatch, the members of the NottICL research group, and the participants in the ISSI ICL working group for many useful discussions about the nature of ICL and measurement techniques. JBGM gratefully acknowledges support from the Leverhulme Trust.

Funding: Funding for the DES Projects has been provided by the U.S. Department of Energy, the U.S. National Science Foundation, the Ministry of Science and Education of Spain, the Science and Technology Facilities Council of the United Kingdom, the Higher Education Funding Council for England, the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, the Kavli Institute of Cosmological Physics at the University of Chicago, the Center for Cosmology and Astro-Particle Physics at the Ohio State University, the Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M University, Financiadora de Estudos e Projetos, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Científico e Tecnológico and the Ministério da Ciência, Tecnologia e Inovação, the Deutsche Forschungsgemeinschaft and the Collaborating Institutions in the Dark Energy Survey.

The Collaborating Institutions are Argonne National Laboratory, the University of California at Santa Cruz, the University of Cambridge, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas-Madrid, the University of Chicago, University College London, the DES-Brazil Consortium, the University of Edinburgh, the Eidgenössische Technische Hochschule (ETH) Zürich, Fermi National Accelerator Laboratory, the University of Illinois at Urbana-Champaign, the Institut de Ciències de l’Espai (IEEC/CSIC), the Institut de Física d’Altes Energies, Lawrence Berkeley National Laboratory, the Ludwig-Maximilians Universität München and the associated Excellence Cluster Universe, the University of Michigan, NSF NOIRLab, the University of Nottingham, The Ohio State University, the University of Pennsylvania, the University of Portsmouth, SLAC National Accelerator Laboratory, Stanford University, the University of Sussex, Texas A&M University, and the OzDES Membership Consortium

Based in part on observations at NSF Cerro Tololo Inter-American Observatory at NSF NOIRLab (NOIRLab Prop. ID 2012B-0001; PI: J. Frieman), which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation.

The DES data management system is supported by the National Science Foundation under grant numbers AST-1138766 and AST-1536171. The DES participants from Spanish institutions are partially supported by MICINN under grants PID2021-123012, PID2021-128989, PID2022-141079, SEV-2016-0588, CEX2020-001058-M, and CEX2020-001007-S, some of which include ERDF funds from the European Union. IFAE is partially funded by the CERCA programme of the Generalitat de Catalunya.

We acknowledge support from the Brazilian Instituto Nacional de Ciênciae Tecnologia (INCT) do e-Universo (CNPq grant 465376/2014-2).

This document was prepared by the DES Collaboration using the resources of the Fermi National Accelerator Laboratory (Fermilab), a U.S. Department of Energy, Office of Science, Office of High Energy Physics HEP User Facility. Fermilab is managed by Fermi Forward Discovery Group, LLC, acting under Contract No. 89243024CSC000002.

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Additional details

Related works

Is new version of
Discussion Paper: arXiv:2409.02184 (arXiv)

Funding

Leverhulme Trust
National Science Foundation
AST-1138766
National Science Foundation
AST-1536171
Ministerio de Ciencia, Innovación y Universidades
PID2021-123012
Ministerio de Ciencia, Innovación y Universidades
PID2021-128989
Ministerio de Ciencia, Innovación y Universidades
PID2022-141079
Ministerio de Ciencia, Innovación y Universidades
SEV-2016-0588
Ministerio de Ciencia, Innovación y Universidades
CEX2020-001058-M
Ministerio de Ciencia, Innovación y Universidades
CEX2020-001007-S
European Commission
National Council for Scientific and Technological Development
465376/2014-2
University of Illinois System
University of Chicago
The Ohio State University
University of California System
University of Cambridge
University College London
University of Edinburgh
University of Pennsylvania
University of Portsmouth
Stanford University
University of Sussex
Texas A&M University
United States Department of Energy
89243024CSC000002

Dates

Accepted
2025-02-12
Available
2025-02-13
Published
Available
2025-03-06
Corrected and typeset

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Caltech groups
Division of Physics, Mathematics and Astronomy (PMA)
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Published