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Overdispersed Radio Source Counts and Excess Radio Dipole Detection.

Lukas Böhme1, Dominik J Schwarz1, Prabhakar Tiwari2

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Astronomers found a significant 5.4σ discrepancy in the cosmic dipole, challenging the standard cosmological model. This finding stems from analyzing radio continuum surveys, suggesting new physics may be needed.

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Area of Science:

  • Cosmology
  • Astrophysics
  • Radio Astronomy

Background:

  • The cosmological standard model is tested using the source count dipole from wide-area radio continuum surveys.
  • Radio source counts distributions can be overdispersed due to multiple components in many sources.

Purpose of the Study:

  • To test the cosmological standard model by analyzing the source count dipole.
  • To account for the overdispersion in source counts using a new Bayesian estimator.

Main Methods:

  • A new Bayesian estimator based on the negative binomial distribution was developed.
  • Data from NVSS, RACS-low, and LoTSS-DR2 wide-area radio surveys were combined.

Main Results:

  • The source count dipole was found to exceed the expected kinematic dipole amplitude from standard cosmology by a factor of 3.67±0.49.
  • This represents a 5.4σ discrepancy, indicating a significant deviation from predictions.

Conclusions:

  • The observed discrepancy challenges the standard cosmological model.
  • Further investigation is needed to understand the cause of this deviation, potentially indicating new physics.