Structural analysis of massive galaxies using HST deep imaging at z <
  0.5
  Taking advantage of HST CANDELS data, we analyze the lowest redshift (z<0.5)
massive galaxies in order to disentangle their structural constituents and
study possible faint non-axis-symmetric features. Due to the excellent HST
spatial resolution for intermediate-z objects, they are hard to model by purely
automatic parametric fitting algorithms. We performed careful single and double
S\'ersic fits to their galaxy surface brightness profiles. We also compare the
model color profiles with the observed ones and also derive multi-component
global effective radii attempting to obtain a better interpretation of the
mass-size relation. Additionally, we test the robustness of our measured
structural parameters via simulations. We find that the S\'ersic index does not
offer a good proxy for the visual morphological type for our sample of massive
galaxies. Our derived multi-component effective radii give a better description
of the size of our sample galaxies than those inferred from single S\'ersic
models with GALFIT. Our galaxy population lays on the scatter of the local
mass-size relation, indicating that these massive galaxies do not experience a
significant growth in size since z~0.5. Interestingly the few outliers are
late-type galaxies, indicating that spheroids must reach the local mass-size
relation earlier. For most of our sample galaxies, both single and
multi-component S\'ersic models with GALFIT show substantial systematic
deviations from the observed SBPs in the outskirts. These residuals may be
partly due to several factors, namely a non-optimal data reduction for low
surface brightness features, the existence of prominent stellar haloes for
massive galaxies and could also arise from conceptual shortcomings of
parametric 2D image decomposition tools. They consequently propagate into
galaxy color profiles.
