Cosmic flows in the nearby universe from Type Ia supernovae

Abstract

Peculiar velocities are one of the only probes of very large scale mass density fluctuations in the nearby Universe. We present new 'minimal variance' bulk flow measurements based upon the 'First Amendment' compilation of 245 Type Ia supernovae (SNe) peculiar velocities and find a bulk flow of 249 +/- 76 km s(-1) in the direction l = 319 degrees +/- 18 degrees, b = 7 degrees +/- 14 degrees. The SNe bulk flow is consistent with the expectations of Lambda cold dark matter (Lambda CDM). However, it is also marginally consistent with the bulk flow of a larger compilation of non-SNe peculiar velocities. By comparing the SNe peculiar velocities to predictions of the IRAS Point Source Catalogue Redshift Survey (PSCz) galaxy density field, we find Omega(0.55)(m) sigma(8,lin) = 0.40 +/- 0.07, which is in agreement with Lambda CDM. However, we also show that the PSCz density field fails to account for 150 +/- 43 km s(-1) of the SNe bulk motion.