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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 APA «a 3° with respect to the inner disc, whereas NGC 4452 harbours a discy outer structure with APA «a 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 IC3381). 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.

Translated title of the contributionНаклонные внешние и внутренние структуры в видимых с ребра галактиках?
Original languageEnglish
Pages (from-to)2039-2056
Number of pages18
JournalMonthly Notices of the Royal Astronomical Society
Volume497
Issue number2
DOIs
StatePublished - Sep 2020

    Scopus subject areas

  • Physics and Astronomy(all)
  • Astronomy and Astrophysics
  • Space and Planetary Science

    Research areas

  • Galaxies: evolution, Galaxies: formation, Galaxies: haloes, Galaxies: interactions, Galaxies: photometry, Galaxies: structure, DISC GALAXIES, STELLAR HALOES, SPIRAL GALAXIES, galaxies: evolution, galaxies: interactions, galaxies: photometry, DARK-MATTER HALOES, STAR-FORMATION, ACS-VIRGO-CLUSTER, COOL INTERSTELLAR-MEDIUM, galaxies: formation, galaxies: structure, DIGITAL SKY SURVEY, ANGULAR-MOMENTUM DISTRIBUTION, MILKY-WAY, galaxies: haloes

ID: 61089968