  We consider the largest sample of 561 edge-on galaxies observed with integral
field units by the MaNGA survey and find 300 galaxies where the ionised gas
shows a negative vertical gradient (lag) in its rotational speed. We introduce
the stop altitude as the distance to the galactic midplane at which the gas
rotation should stop in the linear approximation. We find correlations between
the lags, stop altitude and galactic mass, stellar velocity dispersion and
overall Sersic index. We do not find any correlation of the lags or stop
altitude with the star formation activity in the galaxies. We conclude that low
mass galaxies (log(M*/Mo) < 10) with low Sersic index and with low stellar
velocity dispersion posses a wider "zone of influence" in the extragalactic gas
surrounding them with respect to higher mass galaxies that have a significant
spherical component. We estimated the trend of the vertical rotational gradient
with radius and find it flat for most of the galaxies in our sample. A small
subsample of galaxies with negative radial gradients of lag has an enhanced
fraction of objects with aged low surface brightness structures around them
(e.g. faint shells), which indicates that noticeable accretion events in the
past affected the extraplanar gas kinematics and might have contributed to
negative radial lag gradients. We conclude that an isotropic accretion of gas
from the circumgalactic medium plays a significant role in the formation of
rotation velocity lags.
