Testing the Cosmological Principle in the radio sky

Abstract

The Cosmological Principle states that the Universe is statistically isotropic and homogeneous on large scales. In particular, this implies statistical isotropy in the galaxy distribution, after removal of a dipole anisotropy due to the observer's motion. We test this hypothesis with number count maps from the NVSS radio catalogue. We use a local variance estimator based on patches of different angular radii across the sky and compare the source count variance between and within these patches. In order to assess the statistical significance of our results, we simulate radio maps with the NVSS specifications and mask. We conclude that the NVSS data is consistent with statistical isotropy.

arXiv comment7 pages, 3 figures. To appear in JCAP

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• Cross-correlating radio continuum surveys and CMB lensing: constraining redshift distributions, galaxy bias and cosmology
• The multipole expansion of the local expansion rate
• Measuring the cosmic homogeneity scale with SDSS-IV DR16 Quasars
• The galaxy power spectrum from TGSS ADR1 and the effect of flux calibration systematics
• A study of Dipolar Signal in distant Quasars with various observables
• Big Bang in Dipole Cosmology
• Horizon, homogeneity and flatness problems -- do their resolutions really depend upon inflation?
• Cross-correlating the EMU Pilot Survey 1 with CMB lensing: Constraints on cosmology and galaxy bias with harmonic-space power spectra