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The structural evolution of galaxies with both thin and thick discs

Monthly Notices of the Royal Astronomical Society, ISSN: 1365-2966, Vol: 470, Issue: 2, Page: 2113-2132
2017
  • 18
    Citations
  • 0
    Usage
  • 18
    Captures
  • 0
    Mentions
  • 0
    Social Media
Metric Options:   Counts1 Year3 Year

Metrics Details

  • Citations
    18
    • Citation Indexes
      18
  • Captures
    18

Article Description

We perform controlled N-body simulations of disc galaxies growing within live dark matter (DM) haloes to present-day galaxies that contain both thin and thick discs. We consider two types of models: (a) thick-disc initial conditions to which stars on near-circular orbits are continuously added over ∼10 Gyr, and (b) models in which the birth velocity dispersion of stars decreases continuously over the same time-scale. We show that both schemes produce double-exponential vertical profiles similar to that of the Milky Way (MW). We indicate how the spatial age structure of galaxies can be used to discriminate between scenarios. We show that the presence of a thick disc significantly alters and delays bar formation and thus makes possible models with a realistic bar and a high baryon-to-DM mass ratio in the central regions, as required by microlensing constraints. We examine how the radial mass distribution in stars andDMis affected by disc growth and non-axisymmetries.We discuss howbar buckling shapes the vertical age distribution of thin- and thick-disc stars in the bar region. The extent to which the combination of observationally motivated inside-out growth histories and cosmologically motivated dark halo properties leads to the spontaneous formation of non-axisymmetries that steer the models towards present-day MW-like galaxies is noteworthy.

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