  Among the many processes involved in galaxy evolution, those of bar
formation, quenching, and feedback from an active galactic nucleus (AGN) seem
to be connected, however, the nature of these relations remains unclear. In
this work, we aim to elucidate them by studying the formation of a barred
galaxy in a major merger of two disks in the IllustrisTNG simulations. This
merger involves a coalescence of two supermassive black holes and a sudden
switch to the kinetic mode of AGN feedback implemented in the simulations,
which leads to the removal of the gas from the inner part of the galaxy,
followed by quenching of star formation and the formation of the bar. This
causal relation between AGN feedback and bar formation explains a number of
correlations observed in the data, such as the higher frequency of bars among
red spirals and the presence of central gas holes in barred galaxies. In such a
picture, the bars do not feed the black holes, so their presence does not
increase the AGN strength, and they do not cause quenching. However, bars do
form in regions characterized by a low gas fraction resulting from AGN
feedback. This scenario is probably applicable to many barred galaxies, not
only those formed in major mergers.
