Bibcode
Molaeinezhad, A.; Zhu, L.; Falcón-Barroso, J.; van de Ven, G.; Méndez-Abreu, J.; Balcells, M.; Aguerri, J. A. L.; Vazdekis, A.; Khosroshahi, H. G.; Peletier, R. F.
Bibliographical reference
Monthly Notices of the Royal Astronomical Society, Volume 488, Issue 1, p.1012-1025
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9
2019
Citations
4
Refereed citations
4
Description
We construct Schwarzschild orbit-based models of NGC 7457, known as a
peculiar low-mass lenticular galaxy. Our best-fitting model successfully
retrieves most of the unusual kinematics behaviours of this galaxy, in
which, the orbital distribution of stars is dominated by warm and hot
orbits. The reconstructed surface brightness of the hot component
matches fairly well the photometric bulge and the reconstructed LOSVD
map of this component shows clear rotation around the major photometric
axis of the galaxy. In the absence of a dominant cold component, the
outer part of our model is dominated by warm orbits, representing an
exponential thick disc. Our orbital analysis also confirms the existence
of a counter-rotating orbital substructure in the very centre, reported
in previous observational studies. By comparing our model with a variety
of simulation studies, and considering the stellar kinematics and
populations properties of this galaxy, we suggest that the thick disc is
most likely a dynamically heated structure, formed through the
interactions and accretion of satellite(s) with near-polar initial
inclination. We also suggest a merger-driven process as the most
plausible scenario to explain the observed and dynamically modelled
properties of the bulge of NGC 7457. We conclude that both the high
level of cylindrical rotation and unusually low velocity dispersion
reported for the NGC 7457 have most likely external origins. Therefore,
NGC 7457 could be considered as a candidate for merger-driven
cylindrical rotation in the absence of a strong bar in disc galaxies.
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