Velocity–density correlations from the cosmicflows-3 distance catalogue and the 2MASS Redshift Survey

The peculiar velocity of a mass tracer is on average aligned with the dipole modulation of the surrounding mass density field. We present a first measurement of the correlation between radial peculiar velocities of objects in the cosmicflows-3 catalog and the dipole moment of the 2MRS galaxy distribution in concentric spherical shells centered on these objects. Limiting the analysis to cosmicflows-3 objects with distances of 100 Mpc h^-1, the correlation function is detected at a confidence level > 4. The measurement is found consistent with the standard CDM model at < 1. 7 level. We formally derive the constraints 0. 32<^0. 55₈<0. 48 (68\% confidence level) or equivalently 0. 34<^0. 55/b<0. 52, where b is the galaxy bias factor. Deeper and improved peculiar velocity catalogs will substantially reduce the uncertainties, allowing tighter constraints from this type of correlations.