The Velocity Field from Type Ia Supernovae Matches the Gravity Field from Galaxy Surveys

We compare the peculiar velocities of nearby SNe Ia with those predicted by the gravity fields of full sky galaxy catalogs. The method provides a powerful test of the gravitational instability paradigm and strong constraints on the density parameter β ≡ Ω/b. For 24 SNe Ia within 10,000 km s, we find the observed SNe Ia peculiar velocities are well modeled by the predictions derived from the 1.2 Jy IRAS survey and the Optical Redshift Survey (ORS). Our best β is 0.4 from IRAS, and 0.3 from the ORS, with β > 0.7 and β < 0.15 ruled out at 95% confidence levels from the IRAS comparison. Bootstrap resampling tests show these results to be robust in the mean and in its error. The precision of this technique will improve as additional nearby SNe Ia are discovered and monitored. subject headings: supernovae:general ; cosmology:observations, large-scale structure of universe—Local Group