8-12 juin, 2014


New constraints on cosmological parameters from the comparison of peculiar velocities with predictions from 2M++

Jonathan Carrick (University of Waterloo)

Mike Hudson (University of Waterloo)
Stephen Turnbull (University of Waterloo)
Guilhem Lavaux (Institut d'Astrophysique de Paris)

Peculiar velocities are the only probe of the matter distribution on very large scales in the nearby, low-redshift Universe. While the LCDM model is generally successful, there is some tension between the normalization of the power spectrum of density fluctuations on large scales (via bulk flows), those on smaller scales (via infall into superclusters), and those recently obtained via Planck and WMAP. We present updated constraints on the parameter space of the matter density and root mean-square density contrast within an 8 Mpc/h sphere. These constraints are obtained from the comparison of observed peculiar velocities with the predictions from a recently-constructed deep galaxy redshift compilation, 2M++, which draws from 6df, SDSS and 2MRS redshift surveys (Lavaux & Hudson 2011). The velocity of the Local Group as predicted from 2M++ is in excellent agreement with the direction of the dipole observed in the CMB (within ~10 degrees), however, the amplitude falls short by ~150 km/s, suggesting that either there are significant density fluctuations on scales > 200 Mpc/h, or that the linear biasing model is not accurately predicting the mass density field within 200 Mpc/h.
(doit être confirmé par le SOC)