Probing bulk flow with nearby SNe Ia data
  We test the isotropy of the local Universe using low redshift supernova data
from various catalogs and the non-parametric method of smoothed residuals.
Using a recently developed catalog which combines supernova data from various
surveys, we show that the isotropic hypothesis of a Universe with zero velocity
perturbation can be rejected with moderate significance, with $p$-value $\sim
0.07$ out to redshift $z < 0.045$. We estimate the direction of maximal
anisotropy on the sky for various pre-existing catalogs and show that it
remains relatively unaffected by the light curve fitting procedure. However the
recovered direction is biased by the underlying distribution of data points on
the sky. We estimate both the uncertainty and bias in the direction by creating
mock data containing a randomly oriented bulk flow and using our method to
reconstruct its direction. We conclude that the inhomogeneous nature of the
data introduces a directional bias in galactic latitude of approximately
$|\Delta b_{\rm max}| \sim 18^{\circ}$ for the supernova catalog considered in
this work, and after correcting for this effect we infer the direction of
maximum anisotropy as $(b,\ell) = (20^{\circ}, 276^{\circ}) \pm
(12^{\circ},29^{\circ})$ in galactic coordinates. Finally we compare the
anisotropic signal in the data to mock realisations in which large scale
velocity perturbations are consistently accounted for at the level of linear
perturbation theory. We show that including the effect of the velocity
perturbation in our mock catalogs degrades the significance of the anisotropy
considerably, with $p$-value increasing to $\sim 0.29$. One can conclude from
our analysis that there is a moderate deviation from isotropy in the supernova
data, but the signal is consistent with a large scale bulk velocity expected
within $\Lambda$CDM.
