Mon. Not. R. Astron. Soc., 497, 2039-2056 (2020/September-2)
Tilted outer and inner structures in edge-on galaxies?
MOSENKOV A.V., SMIRNOV A.A., SIL'CHENKO O.K., RICH R.M., RESHETNIKOV V.P. and KORMENDY J.
Abstract (from CDS):
Tilted and warped discs inside tilted dark matter haloes are predicted from numerical and semi-analytical studies. In this paper, we use deep imaging to demonstrate the likely existence of tilted outer structures in real galaxies. We consider two SB0 edge-on galaxies, NGC 4469 and NGC 4452, which exhibit apparent tilted outer discs with respect to the inner structure. In NGC 4469, this structure has a boxy shape, inclined by ΔPA ≃ 3° with respect to the inner disc, whereas NGC 4452 harbours a discy outer structure with ΔPA ≃ 6°. In spite of the different shapes, both structures have surface brightness profiles close to exponential and make a large contribution (∼30 per cent) to the total galaxy luminosity. In the case of NGC 4452, we propose that its tilted disc likely originates from a former fast tidal encounter (probably with IC 3381). For NGC 4469, a plausible explanation may also be galaxy harassment, which resulted in a tilted or even a tumbling dark matter halo. A less likely possibility is accretion of gas-rich satellites several Gyr ago. New deep observations may potentially reveal more such galaxies with tilted outer structures, especially in clusters. We also consider galaxies, mentioned in the literature, where a central component (a bar or a bulge) is tilted with respect to the stellar disc. According to our numerical simulations, one of the plausible explanations of such observed 'tilts' of the bulge/bar is a projection effect due to a not exactly edge-on orientation of the galaxy coupled with a skew angle of the triaxial bulge/bar.
© 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
galaxies: evolution - galaxies: formation - galaxies: haloes - galaxies: interactions - galaxies: photometry - galaxies: structure
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