Tilted outer and inner structures in edge-on galaxies?
  Tilted and warped discs inside tilted dark matter haloes are predicted from
numerical and semi-analytical studies. In this paper, we use deep imaging to
demonstrate the likely existence of tilted outer structures in real galaxies.
We consider two SB0 edge-on galaxies, NGC4469 and NGC4452, which exhibit
apparent tilted outer discs with respect to the inner structure. In NGC4469,
this structure has a boxy shape, inclined by $\Delta$PA$\approx$3$^{\circ}$
with respect to the inner disc, whereas NGC4452 harbours a discy outer
structure with $\Delta$PA$\approx$6$^{\circ}$. In spite of the different
shapes, both structures have surface brightness profiles close to exponential
and make a large contribution ($\sim30$%) to the total galaxy luminosity. In
the case of NGC4452, we propose that its tilted disc likely originates from a
former fast tidal encounter (probably with IC3381). For NGC4469, a plausible
explanation may also be galaxy harassment, which resulted in a tilted or even a
tumbling dark matter halo. A less likely possibility is accretion of gas-rich
satellites several Gyr ago. New deep observations may potentially reveal more
such galaxies with tilted outer structures, especially in clusters. We also
consider galaxies, mentioned in the literature, where a central component (a
bar or a bulge) is tilted with respect to the stellar disc. According to our
numerical simulations, one of the plausible explanations of such observed
"tilts" of the bulge/bar is a projection effect due to a not exactly edge-on
orientation of the galaxy coupled with a skew angle of the triaxial bulge/bar.
