  The formation and evolution of gravitationally bound, star forming
substructures in tidal tails of interacting galaxies, called tidal dwarf
galaxies (TDG), has been studied, until now, only in idealised simulations of
individual pairs of interacting galaxies for pre-determined orbits, mass
ratios, and gas fractions. Here, we present the first identification of TDG
candidates in fully cosmological simulations, specifically the high-resolution
simulations of the EAGLE suite. The finite resolution of the simulation limits
their ability to predict the exact formation rate and survival timescale of
TDGs, but we show that gravitationally bound baryonic structures in tidal arms
already form in current state-of-the-art cosmological simulations. In this
case, the orbital parameter, disc orientations as well as stellar and gas
masses and the specific angular momentum of the TDG forming galaxies are a
direct consequence of cosmic structure formation. We identify TDG candidates in
a wide range of environments, such as multiple galaxy mergers, clumpy
high-redshift (up to z = 2) galaxies, high-speed encounters, and tidal
interactions with gas-poor galaxies. We present selection methods, the
properties of the identified TDG candidates and a roadmap for more quantitative
analyses using future high-resolution simulations.
