Formation of S0 galaxies through mergers. Morphological properties:
  tidal relics, lenses, ovals, and other inner components
  Major mergers are popularly considered too destructive to produce the relaxed
regular structures and the morphological inner components (ICs) usually
observed in lenticular (S0) galaxies. We aim to test if major mergers can
produce remnants with realistic S0 morphologies. We have selected a sample of
relaxed discy remnants resulting from the dissipative merger simulations of the
GalMer database and derived their properties mimicking the typical conditions
of current observational data. We compare their global morphologies, visual
components, and merger relics in mock photometric images with their real
counterparts. Only $\sim$1-2 Gyr after the full merger, we find that: 1) many
remnants (67 major and 29 minor events) present relaxed structures and typical
S0 or E/S0 morphologies, for a wide variety of orbits and even in gas-poor
cases. 2) Contrary to popular expectations, most of them do not exhibit any
morphological traces of their past merger origin under typical observing
conditions and at distances as nearby as 30 Mpc. 3) The merger relics are more
persistent in minor mergers than in major ones for similar relaxing time
periods. 4) No major-merger S0-like remnant develops a significant bar. 5)
Nearly 58% of the major-merger S0 remnants host visually detectable ICs, such
as embedded inner discs, rings, pseudo-rings, inner spirals, nuclear bars, and
compact sources, very frequent in real S0s too. 6) All remnants contain a lens
or oval, identically ubiquitous in local S0s. 7) These lenses and ovals do not
come from bar dilution in major merger cases, but are associated with stellar
halos or embedded inner discs instead (thick or thin). We conclude that the
relaxed morphologies, lenses, ovals, and other ICs of real S0s do not
necessarily come from internal secular evolution, gas infall or environmental
mechanisms, as traditionally assumed, but they can result from major mergers as
well.
