Exploring the outskirts of the EAGLE disc galaxies
  Observations show that the surface brightness of disc galaxies can be
well-described by a single exponential (TI), up-bending (TIII) or down-bending
(TII) profiles in the outskirts. Here we characterize the mass surface
densities of simulated late-type galaxies from the EAGLE project according to
their distribution of mono-age stellar populations, the star formation activity
and angular momentum content. We find that the inner scale-lengths of TII
galaxies correlate with their stellar spin parameter $\lambda$, while those
with TI and TIII profiles show a correlation only for $\lambda>0.35$. The outer
scale-lengths of TII and TIII discs show a positive trend with $\lambda$,
albeit weaker for the latter. TII discs prefer fast rotator galaxies. With
regards to the stellar age distribution, negative and U-shape age profiles are
the most common for all disc types. Positive age profiles are determined by a
more significant contributions of young stars in the central regions, which
decrease rapidly in the outer parts. TII discs prefer relative higher
contributions of old stars compared to other mono-age populations across the
discs whereas TIII discs become progressively more dominated by intermediate
age (2-6 Gyrs) stars for increasing radius. The change in slope of the age
profiles is located after the break of the mass surface density. We find
evidence of larger flaring for the old stellar populations in TI and TIII
systems compared to TII. Overall, the relative distributions of mono-age
stellar populations and the dependence of star formation on radius is found to
modulate the different disc types and age profiles.
