On the quiescence of the Hubble flow in the vicinity of the Local Group -: A study using galaxies with distances from the Cepheid PL-relation

Cepheid distances of local galaxies (<7 Mpc) are used to study the very nearby velocity field, as pioneered by Sandage (1986) who also pointed out its remarkable properties: linearity and quietness. The new data show that the velocity dispersion in the distance range as seen from the barycentre of the Local Group 1-8 Mpc is as low as 38 kms(-1). The local rate of expansion coincides with the global Hubble constant. Down to 1.5 Mpc we cannot detect a deviation from the linear Hubble flow. This puts an upper limit for the mass of the Local Group, for a wide class of Friedman models, including those with the cosmological constant.