We investigate galaxy groups that reside in the field but have been previously processed by galaxy clusters. Observationally, they would appear to have the same properties as regular field groups at first glance. However, one would expect to find quantifiable differences in processed groups as dynamical interactions within clusters perturb them. We use IllustrisTNG300 simulation to statistically quantify that processed groups of galaxies show different properties compared to regular field groups.

Our analysis encompasses a broad range of groups with total masses between 8 × 1011 M⊙ and 7 × 1013 M⊙. We distinguish between processed groups that passed through a galaxy cluster and capture more galaxies, referred to as thief groups, and groups that did not capture any new members, referred to as non-thief groups. The employed statistical tools show that thief groups are generally less compact and contain more members, while non-thief groups seem to have the same properties as the field groups which makes them indistinguishable.