Creating S0s with major mergers : a 3D view

Abstract

Miguel Querejeta, Glenn van de Ven and Jesús Falcón-Barroso acknowledge financial support to the Detailed Anatomy of Galaxies (DAGAL) network from the People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme FP7/2007- 2013/ under REA grant agreement number PITN-GA-2011-289313. M. Carmen Eliche-Moral acknowledges support from the Spanish Ministry of Economy and Competitiveness (MINECO) under projects AYA2012-31277 and AYA2013-48226-C3-1-P. Jairo Méndez-Abreu acknowledges support from the European Research Council Starting Grant (SEDmorph; P.I.V. Wild).A number of simulators have argued that major mergers can sometimes preserve discs, 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 our recent papers 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. Additionally, 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 λ 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.Publisher PDFPeer reviewe