Dipole anisotropy in integrated linearly polarized flux density in NVSS data

Prabhakar Tiwari, Pankaj Jain*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

42 Scopus citations


We study the dipole anisotropy in integrated linearly polarized flux density in NRAO VLA Sky Survey. We extract the anisotropy in the number counts of significantly polarized sources. These are identified by imposing the cut on polarized flux (P), 1.0 < P < 100 mJy, and independently on the degree of polarization (p), 0.03 < p < 1. We also study the anisotropy in observables, PI and pI, defined as the number counts weighted by P and p, respectively. We consider data with several different cuts on the flux density, S > 20, 30, 40, 50, 75 mJy. We find a very significant signal of dipole, both in number counts and P- or p-weighted number counts. We identify and remove a polar angle, θ, dependent bias, centred at the detector array location. We find that the dipole parameters for the case of PI are relatively independent of the cut on S and study it in greater detail. The amplitude of the observed anisotropy is found to be much larger in comparison to the CMBR expectations. The direction is found to be in rough agreement with the CMBR dipole.

Original languageEnglish
Pages (from-to)2658-2670
Number of pages13
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
StatePublished - 1 Mar 2015
Externally publishedYes


  • Cosmology: miscellaneous
  • Galaxies: active
  • Galaxies: high-redshift
  • Polarization


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