Tidal evolution of galaxies in the most massive cluster of
  IllustrisTNG-100
  We study the tidal evolution of galaxies in the most massive cluster of the
IllustrisTNG-100 simulation. For the purpose of this work we select 112
galaxies with the largest stellar masses at present and follow their properties
in time. Using their orbital history we divide the sample into unevolved
(infalling), weakly evolved (with one pericenter passage) and strongly evolved
(with multiple pericenters). The samples are clearly separated by the value of
the integrated tidal force from the cluster the galaxies experienced during
their entire evolution and their properties depend strongly on this quantity.
As a result of tidal stripping, the galaxies of the weakly evolved sample lost
between 10 and 80% of their dark mass and less than 10% of stars, while those
in the strongly evolved one more than 70% of dark and between 10 and 55% of
stellar mass, and are significantly less or even not dark matter dominated.
While 33% of the infalling galaxies do not contain any gas, this fraction
increases to 67% for the weakly evolved and to 100% for the strongly evolved
sample. The strongly evolved galaxies lose their gas earlier and faster (within
2-6 Gyr) but the process can take up to 4 Gyr from the first pericenter
passage. These galaxies are redder and more metal rich, and at redshift z=0.5
the population of galaxies in the cluster becomes predominantly red. As a
result of tidal stirring, the morphology of the galaxies evolves from oblate to
prolate and their rotation is diminished thus the morphology-density relation
is reproduced in the simulated cluster. The strongly evolved sample contains at
least six convincing examples of tidally induced bars and six more galaxies
that had their bars enhanced by their interaction with the cluster.
