Detalles de publicación
PP 014073
Formation of S0 galaxies through mergers
1 Departamento de Astrofísica y CC. de la Atmósfera, Universidad Complutense de Madrid, E-28040 Madrid, Spain
e-mail: asborlaff@ucm.es
2 Max-Planck-Institut für Astronomie, Königstuhl, 17, 69117 Heidelberg, Germany
3 Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. 106, Ensenada BC 22800, Mexico
4 Instituto de Astrofísica de Canarias, C/ Vía Láctea, E-38200 La Laguna, Tenerife, Spain
5 Facultad de Física, Universidad de La Laguna, Avda. Astrofísico Fco. Sánchez s/n, 38200, La Laguna, Tenerife, Spain
6 Consejo Superior de Investigaciones Científicas, Spain
Context. Lenticular galaxies (S0’s) 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.
Aims. We have investigated whether major mergers can result into S0-like remnants with realistic antitruncated stellar discs or not.
Methods. 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 have been quantitatively characterized to compare with real
data.
Results. Nearly 70% of our S0-like remnants are antitruncated, meaning that major mergers that result in S0’s 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, due to the higher luminosities and sizes of the simulations compared
to observational samples. 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 S0’s, which are also reproduced by our simulations. We
show that the trends in all the photometric planes can be derived from three basic scaling relations that real and simulated Type-III
S0’s fulfill: hi ∝ RbrkIII, ho ∝ RbrkIII, and μbrkIII ∝ RbrkIII, where hi and ho are the scalelenghts of the inner and outer discs, and μbrkIII and
RbrkIII are the surface brightness and radius of the breaks. Bars and antitruncations in real S0’s are structurally unrelated phenomena
according to the studied photometric planes.
Conclusions. Mayor mergers provide a feasible mechanism to form realistic antitruncated S0 galaxies.
Major mergers are popularly considered too violent mechanisms to form these breaks.
Aims. We have investigated whether major mergers can result into S0-like remnants with realistic antitruncated stellar discs or not.
Methods. 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 have been quantitatively characterized to compare with real
data.
Results. Nearly 70% of our S0-like remnants are antitruncated, meaning that major mergers that result in S0’s 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, due to the higher luminosities and sizes of the simulations compared
to observational samples. 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 S0’s, which are also reproduced by our simulations. We
show that the trends in all the photometric planes can be derived from three basic scaling relations that real and simulated Type-III
S0’s fulfill: hi ∝ RbrkIII, ho ∝ RbrkIII, and μbrkIII ∝ RbrkIII, where hi and ho are the scalelenghts of the inner and outer discs, and μbrkIII and
RbrkIII are the surface brightness and radius of the breaks. Bars and antitruncations in real S0’s are structurally unrelated phenomena
according to the studied photometric planes.
Conclusions. Mayor mergers provide a feasible mechanism to form realistic antitruncated S0 galaxies.