Formation of S0 galaxies through mergers. V. Antitruncated stellar discs
  resulting from major mergers
  Lenticular galaxies (S0s) are more likely to host antitruncated (Type-III)
stellar discs than galaxies of later Hubble types. Major mergers are popularly
considered too violent mechanisms to form these breaks. We have investigated
whether major mergers can result into S0-like remnants with realistic
antitruncated stellar discs or not. We have analysed 67 relaxed S0 and E/S0
remnants resulting from dissipative N-body simulations of major mergers from
the GalMer database. We have simulated realistic R-band surface brightness
profiles of the remnants to identify those with antitruncated stellar discs.
Their inner and outer discs and the breaks are quantitatively characterized to
compare with real data. Nearly 70% of our S0-like remnants are antitruncated,
meaning that major mergers that result in S0s have a high probability of
producing Type-III stellar discs. Our remnants lie on top of the extrapolations
of the observational trends (towards brighter magnitudes and higher break
radii) in several photometric diagrams. In scale-free photometric diagrams,
simulations and observations overlap and the remnants reproduce the
observational trends, so the physical mechanism after antitruncations is highly
scalable. We have found novel photometric scaling relations between the
characteristic parameters of the antitruncations in real S0s, which are also
reproduced by our simulations. The trends in all the photometric planes can be
derived from three basic scaling relations that real and simulated Type-III S0s
fulfill: h_i \prop R_brkIII, h_o \prop R_brkIII, and mu_brkIII \prop R_brkIII,
where h_i and h_o are the scalelenghts of the inner and outer discs, and
mu_brkIII and R_brkIII are the surface brightness and radius of the breaks.
Mayor mergers provide a feasible mechanism to form realistic antitruncated S0
galaxies (abridged).
