Bibcode
Prieto, M.; Balcells, M.; Zamorano, J.; Gallego, J.; Aguerri, J. A. L.; González-García, A. C.; Eliche-Moral, M. C.
Bibliographical reference
Astronomy and Astrophysics, Volume 552, id.A67, 13 pp.
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4
2013
Journal
Citations
27
Refereed citations
27
Description
Context. Galaxy mergers are widely discussed as one possible evolution
mechanism for lenticular galaxies (S0s), because even minor mergers
induce structural changes that are difficult to reconcile with the
strong bulge-disk coupling observed in the photometric scaling relations
of these galaxies. Aims: We check if the evolution induced onto
S0s by dry intermediate and minor mergers can reproduce the S0
photometric scaling relations. Methods: We analyse the bulge-disk
decompositions of the collisionless N-body simulations of intermediate
and minor mergers onto S0s presented previously to determine the
evolution induced by the mergers in several relevant photometric planes.
Results: The mergers induce an evolution in the photometric
planes that is compatible with the data of S0s, even in the relations
that indicate a strong bulge-disk coupling. Mergers drive the formation
of the observed photometric relation in some cases and induce a slight
dispersion compatible with data in others. Therefore, this evolutionary
mechanism tends to preserve the observational photometric relations. In
the photometric planes where the morphological types segregate, the
mergers always induce evolution towards the region populated by S0s. No
clear trends with the mass ratio of the encounter, the central satellite
density, or the spin-orbit coupling are found for the range of values
studied. Long-pericentre orbits generate more concentrated disks and
expanded bulges than initially, while short-pericentre orbits do the
opposite. The structural coupling of the bulge and the disk is preserved
or reinforced in the models because mergers trigger internal secular
processes in the primary disk that induce significant bulge growth. This
happens even though the encounters do not induce bars in the disks. Conclusions: Intermediate and minor mergers can be considered to be
plausible mechanisms for the evolution of S0s if one includes their
photometric scaling relations, because they can preserve and even
strengthen any pre-existing structural bulge-disk coupling by triggering
significant internal secular evolution, even without bars or
dissipational effects. Satellite accretions thus seem to unavoidably
entail internal secular evolution, meaning that it may be quite complex
to isolate the effects of the internal secular evolution driven by
mergers from the one due to purely intrinsic disk instabilities in
individual early-type disks at the present.
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