Creating S0s with major mergers: a 3D view
  A number of simulators have argued that major mergers can sometimes preserve
discs (e.g. Springel & Hernquist 2005), but the possibility that they could
explain the emergence of lenticular galaxies (S0s) has been generally
neglected. In fact, observations of S0s reveal a strong structural coupling
between their bulges and discs, which seems difficult to reconcile with the
idea that they come from major mergers. However, in Querejeta et al. (2015a) we
have used N-body simulations of binary mergers to show that, under favourable
conditions, discs are first destroyed but soon regrow out of the leftover
debris, matching observational photometric scaling relations (e.g. Laurikainen
et al. 2010). Additionally, in Querejeta et al. (2015b) we have shown how the
merger scenario agrees with the recent discovery that S0s and most spirals are
not compatible in an angular momentum--concentration plane. This important
result from CALIFA constitutes a serious objection to the idea that spirals
transform into S0s mainly by fading (e.g. via ram-pressure stripping, as that
would not explain the observed simultaneous change in $\lambda_\mathrm{Re}$ and
concentration), but our simulations of major mergers do explain that mismatch.
From such a 3D comparison we conclude that mergers must be a relevant process
in the build-up of the current population of S0s.
