Context :

Aims : We use accurate data on distances and radial velocities of galaxies around the Local Group , as well as around 14 other massive nearby groups , to estimate their radius of the zero-velocity surface , R _ { 0 } , which separates any group against the global cosmic expansion .

Methods : Our R _ { 0 } estimate was based on fitting the data to the velocity field expected from the spherical infall model , including effects of the cosmological constant .
The reported uncertainties were derived by a Monte Carlo simulation .

Results : Testing various assumptions about a location of the group barycentre , we found the optimal estimates of the radius to be 0.91 \pm 0.05 Mpc for the Local Group , and 0.93 \pm 0.02 Mpc for a synthetic group stacked from 14 other groups in the Local Volume .
Under the standard Planck model parameters , these quantities correspond to the total mass of the group \sim ( 1.6 \pm 0.2 ) 10 ^ { 12 } M _ { \sun } .
Thus , we are faced with the paradoxical result that the total mass estimate on the scale of R _ { 0 } \approx ( 3 - 4 ) R _ { vir } is only \leavevmode \nobreak 60 % of the virial mass estimate .
Anyway , we conclude that wide outskirts of the nearby groups do not contain a large amount of hidden mass outside their virial radius .

Conclusions :