The NGC 4013 tale: a pseudo-bulged, late-type spiral shaped by a major
  merger
  Many spiral galaxy haloes show stellar streams with various morphologies when
observed with deep images. The origin of these tidal features is discussed,
either coming from a satellite infall or caused by residuals of an ancient,
gas-rich major merger. By modelling the formation of the peculiar features
observed in the NGC 4013 halo, we investigate their origin. By using GADGET -2
with implemented gas cooling, star formation, and feedback, we have modelled
the overall NGC 4013 galaxy and its associated halo features. A gas-rich major
merger occurring 2.7-4.6 Gyr ago succeeds in reproducing the NGC 4013 galaxy
properties, including all the faint stellar features, strong gas warp,
boxy-shaped halo and vertical 3.6 mum luminosity distribution. High gas
fractions in the progenitors are sufficient to reproduce the observed thin and
thick discs, with a small bulge fraction, as observed. A major merger is able
to reproduce the overall NGC 4013 system, including the warp strength, the red
colour and the high stellar mass density of the loop, while a minor merger
model cannot. Because the gas-rich model suffices to create a pseudo-bulge with
a small fraction of the light, NGC 4013 is perhaps the archetype of a late-type
galaxy formed by a relatively recent merger. Then late type, pseudo-bulge
spirals are not mandatorily made through secular evolution, and the NGC 4013
properties also illustrate that strong warps in isolated galaxies may well
occur at a late phase of a gas-rich major merger.
