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Thomas Bensby

Studierektor forskarutbildning

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Young stars in an old bulge: a natural outcome of internal evolution in the Milky Way

Författare

  • M. Ness
  • Victor P. Debattista
  • Thomas Bensby
  • Sofia Feltzing
  • R. Roskar
  • D. R. Cole
  • J. A. Johnson
  • K. Freeman

Summary, in English

The center of our disk galaxy, the Milky Way, is dominated by a boxy/peanut-shaped bulge. Numerous studies of the bulge based on stellar photometry have concluded that the bulge stars are exclusively old. The perceived lack of young stars in the bulge strongly constrains its likely formation scenarios, providing evidence that the bulge is a unique population that formed early and separately from the disk. However, recent studies of individual bulge stars using the microlensing technique have reported that they span a range of ages, emphasizing that the bulge may not be a monolithic structure. In this Letter we demonstrate that the presence of young stars that are located predominantly nearer to the plane is expected for a bulge that has formed from the disk via dynamical instabilities. Using an N-body + smoothed particle hydrodynamics simulation of a disk galaxy forming out of gas cooling inside a dark matter halo and forming stars, we find a qualitative agreement between our model and the observations of younger metal-rich stars in the bulge. We are also able to partially resolve the apparent contradiction in the literature between results that argue for a purely old bulge population and those that show a population comprised of a range in ages; the key is where to look.

Avdelning/ar

  • Lund Observatory - Has been reorganised

Publiceringsår

2014

Språk

Engelska

Publikation/Tidskrift/Serie

Astrophysical Journal Letters

Volym

787

Issue

2

Dokumenttyp

Artikel i tidskrift

Förlag

IOP Publishing

Ämne

  • Astronomy, Astrophysics and Cosmology

Nyckelord

  • Galaxy: bulge
  • Galaxy: evolution
  • Galaxy: formation
  • Galaxy: stellar
  • content

Aktiv

Published

ISBN/ISSN/Övrigt

  • ISSN: 2041-8213