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Brightest Cluster Galaxy ellipticity as proxy for halo shape: Orientation bias, assembly bias, and potential selection effects in SZ-selected clusters

Journal Article · · No journal information
OSTI ID:3028541
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  1. SUNY, Stony Brook
  2. Munich U. Observ.
  3. Argonne; Chicago U., KICP
  4. Southern Methodist U.
  5. Shanghai Jiao Tong U.
  6. ICE, Bellaterra
  7. Princeton U., Astrophys. Sci. Dept.
  8. Cincinnati U.
  9. Wisconsin U., Madison
  10. Argonne (main)
  11. Pennsylvania U., Dept. Math.
  12. Carnegie Mellon U.
  13. IAC, La Laguna; LIneA, Rio de Janeiro; Laguna U., Tenerife
  14. Illinois U., Urbana (main); Illinois U., Urbana, Astron. Dept.
  15. Chicago U., KICP; Chicago U., Astron. Astrophys. Ctr.
  16. Duke U.
  17. NASA, Goddard
  18. Madrid, CIEMAT; Madrid, Escuela Tec. Sup. Ing. Ind.
  19. LBL, Berkeley
  20. Chicago U., KICP; Chicago U., Astron. Astrophys. Ctr.; Fermilab
  21. Pennsylvania U., Dept. Math.; LPSC, Grenoble
  22. Waterloo U.
  23. Caltech
  24. SLAC
  25. Chicago U., KICP; ICE, Bellaterra
  26. Innsbruck U., Inst. Astrophys.
  27. Cardiff U.
  28. Cambridge U., DAMTP
  29. Munich U. Observ.; Princeton U., Astrophys. Sci. Dept.; SLAC; KIPAC, Menlo Park
  30. MIT
  31. Campinas State U.
  32. Nordita; DARK Cosmology Ctr.
  33. INFN, Genoa
  34. Melbourne U.
  35. Jodrell Bank
  36. SLAC; KIPAC, Menlo Park
  37. Barcelona, IFAE; Barcelona, Autonoma U.
  38. MIT; Arkansas U.
  39. Chicago U., KICP
  40. Brookhaven
  41. Chulalongkorn U.
  42. NRAO, Tucson; Natl. Solar Observ., Tucson
  43. Harvard-Smithsonian Ctr. Astrophys.
  44. IRAP, Toulouse
  45. Fermilab
  46. LIneA, Rio de Janeiro; Trieste Observ.
  47. Zurich U.
  48. Portsmouth U., ICG
  49. Northeastern U.
  50. University Coll. London
  51. Queensland U.
  52. Barcelona, IFAE
  53. Trieste Observ.; SISSA, Trieste; INFN, Trieste; IFPU, Trieste
  54. LIneA, Rio de Janeiro
  55. SISSA, Trieste; INFN, Trieste; IFPU, Trieste
  56. Indian Inst. Tech., Hyderabad
  57. Madrid, IFT
  58. UC, Santa Cruz
  59. Caltech, JPL
  60. Texas A-M
  61. LPSC, Grenoble; Marseille, CPPM
  62. Barcelona, IFAE; ICREA, Barcelona
  63. Rio de Janeiro Observ.
  64. Sussex U., Astron. Ctr.
  65. Madrid, CIEMAT; Madrid, Escuela Tec. Sup. Ing. Ind.; Zurich U.
  66. ORNL, Oak Ridge (main)
  67. Illinois U., Urbana (main)
  68. LBL, Berkeley; BCCP, Berkeley; UC, Berkeley
  69. Munich U. Observ.; Garching, Max Planck Inst., MPE
+ Show Author Affiliations
The orientation of triaxial galaxy clusters with respect to the line-of-sight is expected to be one of the prime sources of scatter and potential bias in optical observables (e.g., richness and weak-lensing signal) of galaxy clusters. In this work, we use the observed shape of the central Brightest Cluster Galaxy (BCG) as proxy for the orientation along the line-of-sight for clusters selected via the Sunyaev-Zel'dovich (SZ) effect from the South Pole Telescope (SPT) and Atacama Cosmology Telescope (ACT) surveys, matched to optically selected clusters from the Dark Energy Survey Year 3 (DES). We construct two samples of clusters that are designed to be identical in SZ mass estimate and redshift but with the roundest vs. the most elliptical BCGs, which we expect to correspond to BCGs (and clusters) with major axes aligned along the line-of-sight vs. in the plane of the sky, respectively. We find that the optical richness of round-BCG clusters is $$\sim 10$$% larger than that of elliptical-BCG clusters, in agreement with the expectation from projection effects and presenting the first such detection in data. The density profiles, however, are not in agreement with the expectation from projection effects: the 1-halo term (below $$6~h^{-1}\rm{Mpc}$$) of both the weak-lensing and galaxy density profiles are the same for the subsamples, contrary to previous studies based on X-ray selected clusters. In the 2-halo regime (above $$6~h^{-1}\rm{Mpc}$$), we find a significant excess of the elliptical-BCG cluster profiles compared to the round-BCG cluster profiles, which is the opposite of the expectation from numerical simulations. We hypothesize that the intrinsic shape of the BCG reflects not just the orientation angle, but also intrinsic properties of the cluster which can affect both the SZ signal and the amplitude of the 2-halo term.
Research Organization:
Laguna U., Tenerife; DARK Cosmology Ctr.; UC, Santa Cruz; Brookhaven National Laboratory (BNL), Upton, NY (United States); Marseille, CPPM; Argonne National Laboratory (ANL), Argonne, IL (United States); NRAO, Tucson; Rio de Janeiro Observ.; ICE, Bellaterra; Wisconsin U., Madison; Madrid, Escuela Tec. Sup. Ing. Ind.; Melbourne U.; Madrid, IFT; Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Texas A-M; Caltech, JPL; Pennsylvania U., Dept. Math.; Illinois U., Urbana (main); Garching, Max Planck Inst., MPE; University Coll. London; Natl. Solar Observ., Tucson; Harvard-Smithsonian Ctr. Astrophys.; Jodrell Bank; Cincinnati U.; Nordita; Portsmouth U., ICG; Munich U. Observ.; Barcelona, IFAE; Caltech; LIneA, Rio de Janeiro; INFN, Trieste; Madrid, CIEMAT; Waterloo U.; Duke U.; Campinas State U.; Arkansas U.; IRAP, Toulouse; Cardiff U.; Northeastern U.; Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); Southern Methodist U.; IFPU, Trieste; NASA, Goddard; MIT; INFN, Genoa; Shanghai Jiao Tong U.; BCCP, Berkeley; Zurich U.; ICREA, Barcelona; Princeton U., Astrophys. Sci. Dept.; Innsbruck U., Inst. Astrophys.; UC, Berkeley; SUNY, Stony Brook; Carnegie Mellon U.; IAC, La Laguna; SISSA, Trieste; Trieste Observ.; Sussex U., Astron. Ctr.; Queensland U.; Illinois U., Urbana, Astron. Dept.; Indian Inst. Tech., Hyderabad; SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States); Barcelona, Autonoma U.; Chicago U., KICP; Chicago U., Astron. Astrophys. Ctr.; LPSC, Grenoble; Chulalongkorn U.; Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); Cambridge U., DAMTP
Sponsoring Organization:
US Department of Energy
DOE Contract Number:
89243024CSC000002;
OSTI ID:
3028541
Report Number(s):
FERMILAB-PUB-26-0147-PPD; DES-2025-0908; oai:inspirehep.net:3134198; arXiv:2603.23689
Journal Information:
No journal information, Journal Name: No journal information
Country of Publication:
United States
Language:
English

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