Dipole anisotropy in sky brightness and source count distribution in
  radio NVSS data
  We study the dipole anisotropy in number counts and flux density weighted
number counts {or sky brightness} in the NRAO VLA Sky Survey (NVSS) data. The
dipole anisotropy is expected due to our local motion with respect to the CMBR
rest frame. We analyse data with an improved fit to the number density, n(S),
as a function of the flux density S, which allows deviation from a pure power
law behaviour. We also impose more stringent cuts to remove the contribution
due to clustering dipole. In agreement with earlier results, we find that the
amplitude of anisotropy is significantly larger in comparison to the prediction
based on CMBR measurements. The extracted speed is found to be roughly 3 times
the speed corresponding to CMBR. The significance of deviation is smaller,
roughly 2 sigma, in comparison to earlier estimates. For the cut, S>30 mJy, the
speed is found to be $1110\pm370$ Km/s using the source count analysis. The
direction of the dipole anisotropy is found to be approximately in agreement
with CMBR. We find that the results are relatively insensitive to the lower as
well as upper limit imposed on the flux density. Our results suggest that the
Universe is intrinsically anisotropic with the axis of anisotropy axis pointing
roughly towards the CMBR dipole direction. Finally we present a method which
may allow an independent extraction of the local speed and an intrinsic dipole
anisotropy, provided a larger data set becomes available in future.
