gives $\gamma=0.496\pm 0.096$. Figure (\[fig:gamma\]) confirms this result. The figure plots $\Delta \chi^2$ as a function of $\gamma$ for the adopted values of $\sigma_8$ and $\Omega_m$ as indicated. The left and right arrows mark the values $\gamma=0.42$ and 11/16. The lower value is expected in $f(R)$ models [e.g. @Gann09] and the highest corresponds to a Dvali-Gabadadze-Porrati (DGP) [@DGP; @Wei] flat braneworld cosmology. We could also substitute the scaling with $\gamma$ in the correlation $\sigma_8\sim \Omega_m^{-0.28}$ obtained from the contour plot to get the constraint $\sigma_8\Omega_m^{\gamma-0.55}(\Omega_m/0.266)^{0.28}=0.86\pm 0.11$ between $\gamma$, $\Omega_m$ and $\sigma_8$.

Discussion {#sec:disc}
==========

The analysis presented here uses a trimmed version of the SFI++ in which galaxies fainter than $M=-20$ are removed. This ensures the linearity of the TF relation. Further, to avoid dealing with selection effects imposed on the magnitudes we use the inverse TF relation (see [@sw95] for a thorough review of this issue). Further, to minimize inhomogeneous Malmquist bias [@lyn88], we do not place galaxies at their TF inferred distances, but at their measured redshifts which has significantly smaller observational errors. We also collapse the main known galaxy clusters.

The bulk flows estimated here are remarkably featureless and do not seem to reflect the gravitational effects 