Infall of galaxies onto groups
  Growth of the structure in the Universe manifest as accretion flows of
galaxies onto groups and clusters. Thus, the present day properties of groups
and their member galaxies are influenced by the characteristics of this
continuous infall pattern. Several works both theoretical, in numerical
simulations, and in observations, study this process and provide useful steps
for a better understanding of galaxy systems and their evolution. We aim at
exploring the streaming flow of galaxies onto groups using observational
peculiar velocity data. The effects of distance uncertainties are also analyzed
as well as the relation between the infall pattern and group and environment
properties.This work deals with analysis of peculiar velocity data and their
projection on the direction to group centers, to determine the mean galaxy
infall flow. We applied this analysis to the galaxies and groups extracted from
the Cosmicflows-3 catalog. We also use mock catalogs derived from numerical
simulations to explore the effects of distance uncertainties on the derivation
of the galaxy velocity flow onto groups. We determine the infalling velocity
field onto galaxy groups with cz < 0.033 using peculiar velocity data. We
measure the mean infall velocity onto group samples of different mass range,
and also explore the impact of the environment where the group reside. Well
beyond the group virial radius, the surrounding large-scale galaxy overdensity
may impose additional infalling streaming amplitudes in the range 200 to 400 km
s$^{-1}$. Also, we find that groups in samples with a well controlled galaxy
density environment show an increasing infalling velocity amplitude with group
mass, consistent with the predictions of the linear model. These results from
observational data are in excellent agreement with those derived from the mock
catalogs.
