Formation of S0 galaxies through mergers^⋆

Explaining angular momentum and concentration change from spirals to S0s

¹ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
e-mail: querejeta@mpia-hd.mpg.de
² Departamento de Astrofísica y Ciencias de la Atmósfera, Universidad Complutense de Madrid, 28040 Madrid, Spain
³ Instituto de Astronomía, Universidad Nacional Autónoma de México, BC-22800 Ensenada, Mexico
⁴ Instituto de Astrofísica de Canarias, C/vía Láctea, 38200 La Laguna, Tenerife, Spain
⁵ Kapteyn Astronomical Institute, University of Groningen, Postbus 800, 9700 Groningen, The Netherlands
⁶ School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, KY16 9SS, UK

Received: 19 April 2015
Accepted: 26 May 2015

Abstract

The CALIFA team has recently found that the stellar angular momentum and concentration of late-type spiral galaxies are incompatible with those of lenticular galaxies (S0s), concluding that fading alone cannot satisfactorily explain the evolution from spirals into S0s. Here we explore whether major mergers can provide an alternative way to transform spirals into S0s by analysing the spiral-spiral major mergers from the GalMer database that lead to realistic, relaxed S0-like galaxies. We find that the change in stellar angular momentum and concentration can explain the differences in the λ_Re–R₉₀/R₅₀ plane found by the CALIFA team. Major mergers thus offer a feasible explanation for the transformation of spirals into S0s.