Peculiar Velocities in Cosmology

The Universe is not homogenous. Since the early times, its structures have grown and moved under the laws of gravity. By measuring these motions today we are able to trace the history of the Universe expansion and gravity laws and hence test the General Relativity. Peculiar velocity measurements rely on precise extragalactic distances estimation, which can be provided by type Ia supernovae observations. Because peculiar velocities of galaxies are deviations from the Hubble expansion law, they have poor signal to noise ratio and are particularly sensible to usual systematic uncertainties such as calibration errors, selection effects and unknown covariances. During this presentation I will show how a precise forward modeling of observations allow us to overcome these caveats and that peculiar velocities analyses can be considered as a powerful cosmological probe. In particular, I will detail how the statistical methods I developed during my thesis can handle extragalactic distance measurements and lead to - e.g. - a velocity field reconstruction of our Local Universe from Type Ia Supernovae, so as constraints on General Relativity.

Speaker: Romain Graziani, Universite Blaise Pascal

Room LBL 50-5132