Cosmological Constraints from Type Ia Supernovae Peculiar Velocity Measurements

We detect the correlated peculiar velocities of nearby type Ia supernovae (SNe), while highlighting an error in some of the literature. We find ${\sigma }_8=0.79\pm 0.22$ from SNe, and examine the potential of this method to constrain cosmological parameters in the future. We demonstrate that a survey of 300 low-$z$ SNe (such as the nearby SNfactory) will underestimate the errors on $w$ by $\sim 35\%$ if the coherent peculiar velocities are not included.

Figure 1

The ratio of the covariance from peculiar velocities $C_v$, compared to the random errors $\sigma$, for a pair of supernovae, over a range of angular separations, $\theta$.

Figure 2

95% confidence limits on ${\Omega }_m$ and $w$, for WMAP only (thin black lines), WMAP with high-$z$ SNe (thick red line), and WMAP with all-$z$ SNe including PVs (dotted blue line).

Figure 3

The marginalized $1\sigma$ contours for ${\Omega }_m$ and $w$ from a SNAP-like high-$z$ SNe survey in a flat $\Lambda \mathrm{CDM}$ cosmology (short dashed lines). We also consider including 300 low-$z$ SNe from a SNfactorylike survey, while ignoring peculiar velocities (solid lines) and including them (long dashed lines). Smaller red contours include cosmic variance limited CMB, up to $\ell =2000$.