The effects of AGN feedback on the structural and dynamical properties
  of Milky Way-mass galaxies in cosmological simulations
  Feedback from active galactic nuclei (AGN) has become established as a
fundamental process in the evolution of the most massive galaxies. Its impact
on Milky Way (MW)-mass systems, however, remains comparatively unexplored. In
this work, we use the Auriga simulations to probe the impact of AGN feedback on
the dynamical and structural properties of galaxies, focussing on the bar,
bulge, and disc. We analyse three galaxies -- two strongly and one
unbarred/weakly barred -- using three setups: (i) the fiducial Auriga model,
which includes both radio and quasar mode feedback, (ii) a setup with no radio
mode, and (iii) one with neither the radio nor the quasar mode. When removing
the radio mode, gas in the circumgalactic medium cools more efficiently and
subsequently settles in an extended disc, with little effect on the inner disc.
Contrary to previous studies, we find that although the removal of the quasar
mode results in more massive central components, these are in the form of
compact discs, rather than spheroidal bulges. Therefore, galaxies without
quasar mode feedback are more baryon-dominated and thus prone to forming
stronger and shorter bars, which reveals an anti-correlation between the
ejective nature of AGN feedback and bar strength. Hence, we report that the
effect of AGN feedback (i.e. ejective or preventive) can significantly alter
the dynamical properties of MW-like galaxies. Therefore, the observed dynamical
and structural properties of MW-mass galaxies can be used as additional
constraints for calibrating the efficiency of AGN feedback models.
