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We quantify the effect of supernova Type Ia peculiar velocities on thederivation of cosmological parameters. The published distant and local Ia SNeused for the Supernova Legacy Survey first-year cosmology report form thesample for this study. While previous work has assumed that the local SNe areat rest in the CMB frame (the No Flow assumption), we test this assumption byapplying peculiar velocity corrections to the local SNe using three differentflow models. The models are based on the IRAS PSCz galaxy redshift survey, havevarying beta = Omega_m^0.6/b, and reproduce the Local Group motion in the CMBframe. These datasets are then fit for w, Omega_m, and Omega_Lambda usingflatness or LambdaCDM and a BAO prior. The chi^2 statistic is used to examinethe effect of the velocity corrections on the quality of the fits. The mostfavored model is the beta=0.5 model, which produces a fit significantly betterthan the No Flow assumption, consistent with previous peculiar velocitystudies. By comparing the No Flow assumption with the favored models we derivethe largest potential systematic error in w caused by ignoring peculiarvelocities to be Delta w = +0.04. For Omega_Lambda, the potential error isDelta Omega_Lambda = -0.04 and for Omega_m, the potential error is DeltaOmega_m < +0.01. The favored flow model (beta=0.5) produces the followingcosmological parameters: w = -1.08 (+0.09,-0.08), Omega_m = 0.27 (+0.02,-0.02)assuming a flat cosmology, and Omega_Lambda = 0.80 (+0.08,-0.07) and Omega_m =0.27 (+0.02,-0.02) for a w = -1 (LambdaCDM) cosmology.

The Peculiar Velocities of Local Type Ia Supernovae and their Impact on Cosmology