Probing cosmic anisotropy from galaxy clusters via the dipole fitting method
4 affiliations
- 1Xi’an Jiaotong University
- 2Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education
- 3University of Science and Technology of China
- 4Nanjing University
Abstract
The cosmological principle, as the cornerstone of the standard cosmological model, requires that the universe be homogeneous and isotropic on large scales. As a fundamental assumption, it is constantly subjected to testing via various datasets and methods. In this work, we used the dipole fitting (DF) method to correct the logarithmic luminosity ( log LX log L X ) of galaxy clusters, search for cosmic anisotropic signals, and establish a statistical isotropic analysis scheme. Compared to the type Ia supernovae (SNe Ia), the galaxy clusters offer a superior spatial distribution, which enhances the reliability of the identified anisotropic signals. Using a sample of 313 galaxy clusters (observed by Chandra and XMM-Newton), we identified the preferred direction (l, b) = ( 257.82∘ −52.88+58.01 257 . 82 ∘ - 52.88 + 58.01 , − 31.30∘ −39.46+35.92 - 31.30 ∘ - 39.46 + 35.92 ) of the cosmic anisotropy. The corresponding magnitude of anisotropy is A = − 5.4 × 10−4 - 5.4 × 10 - 4 . Subsample reanalyses categorized by instrumentation (Chandra and XMM-Newton) and redshift (low-redshift, z ≤ 0.10 z ≤ 0.10 ; high-redshift, z > 0.10 z > 0.10 ) revealed more significant anisotropic signals. The XMM-Newton dataset yields a statistical significance of 1.8σ 1.8 σ (Bootstrap) and 1.9σ 1.9 σ (Randomized), which are considerably higher than those from the Chandra or total datasets. Meanwhile, the reanalyses also reveal that the choice of equipment and the sample redshift influence the preferred direction, anisotropic magnitude, and statistical significance obtained from galaxy clusters. Overall, the DF method can be well integrated with galaxy clusters and applied to the detection of cosmic anisotropy. Our results suggest the presence of anisotropic signals in galaxy clusters; however, they do not reach a statistical confidence level sufficient to challenge the cosmological principle. Further tests are still needed to better understand these signals.
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BibTeX
@article{hu2026probing,
title = {{Probing cosmic anisotropy from galaxy clusters via the dipole fitting method}},
author = {J. P. Hu and C. Geng and X. D. Jia and Z. Y. Zuo and T. Z. Yang and F. Y. Wang},
journal = {The European Physical Journal C},
year = {2026},
month = oct,
doi = {10.1140/epjc/s10052-026-16365-w},
url = {https://link.springer.com/article/10.1140/epjc/s10052-026-16365-w},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Probing cosmic anisotropy from galaxy clusters via the dipole fitting method
AU - J. P. Hu
AU - C. Geng
AU - X. D. Jia
AU - Z. Y. Zuo
AU - T. Z. Yang
AU - F. Y. Wang
PY - 2026
DA - 2026/10/22
JO - The European Physical Journal C
DO - 10.1140/epjc/s10052-026-16365-w
UR - https://link.springer.com/article/10.1140/epjc/s10052-026-16365-w
AB - The cosmological principle, as the cornerstone of the standard cosmological model, requires that the universe be homogeneous and isotropic on large scales. As a fundamental assumption, it is constantly subjected to testing via various datasets and methods. In this work, we used the dipole fitting (DF) method to correct the logarithmic luminosity ( log L_X log L X ) of galaxy clusters, search for cosmic anisotropic signals, and establish a statistical isotropic analysis scheme. Compared to the type Ia supernovae (SNe Ia), the galaxy clusters offer a superior spatial distribution, which enhances the reliability of the identified anisotropic signals. Using a sample of 313 galaxy clusters (observed by Chandra and XMM-Newton), we identified the preferred direction (l, b) = ( 257.82^∘ _−52.88^+58.01 257 . 82 ∘ - 52.88 + 58.01 , − 31.30^∘ _−39.46^+35.92 - 31.30 ∘ - 39.46 + 35.92 ) of the cosmic anisotropy. The corresponding magnitude of anisotropy is A = − 5.4 × 10^−4 - 5.4 × 10 - 4 . Subsample reanalyses categorized by instrumentation (Chandra and XMM-Newton) and redshift (low-redshift, z ≤ 0.10 z ≤ 0.10 ; high-redshift, z > 0.10 z > 0.10 ) revealed more significant anisotropic signals. The XMM-Newton dataset yields a statistical significance of 1.8σ 1.8 σ (Bootstrap) and 1.9σ 1.9 σ (Randomized), which are considerably higher than those from the Chandra or total datasets. Meanwhile, the reanalyses also reveal that the choice of equipment and the sample redshift influence the preferred direction, anisotropic magnitude, and statistical significance obtained from galaxy clusters. Overall, the DF method can be well integrated with galaxy clusters and applied to the detection of cosmic anisotropy. Our results suggest the presence of anisotropic signals in galaxy clusters; however, they do not reach a statistical confidence level sufficient to challenge the cosmological principle. Further tests are still needed to better understand these signals.
SN - 1434-6044
SN - 1434-6052
ER -