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Sofia Feltzing

Sofia Feltzing

Professor of astronomy

Sofia Feltzing

The Extremely Metal-rich Knot of Stars at the Heart of the Galaxy

Author

  • Hans Walter Rix
  • Vedant Chandra
  • Gail Zasowski
  • Annalisa Pillepich
  • Sergey Khoperskov
  • Sofia Feltzing
  • Rosemary F.G. Wyse
  • Neige Frankel
  • Danny Horta
  • Juna Kollmeier
  • Keivan Stassun
  • Melissa K. Ness
  • Jonathan C. Bird
  • David Nidever
  • José G. Fernández-Trincado
  • João A.S. Amarante
  • Chervin F.P. Laporte
  • Jianhui Lian
Show all

Summary, in English

We show with Gaia XP spectroscopy that extremely metal-rich (EMR) stars in the Milky Way ([M/H]XP ≳ 0.5) are largely confined to a tight "knot"at the center of the Galaxy. This EMR knot is round in projection, has a fairly abrupt edge near RGC,proj ∼ 1.5 kpc, and is a dynamically hot system. This central knot also contains very metalrich (VMR; +0.2 . [M/H]XP . +0.4) stars. However, in contrast to EMR stars, the bulk of VMR stars forms an extended, highly flattened distribution in the inner Galaxy (RGC ≲5 kpc). We draw on TNG50 simulations of Milky Way analogs for context and find that compact, metal-rich knots confined to ≲1.5 kpc are a universal feature. In typical simulated analogs, the top 5%-10% most metal-rich stars are confined to a central knot; however, in our Milky Way data this fraction is only 0.1%. Dust-penetrating wide-area near-infrared spectroscopy, such as the fifth Sloan Digital Sky Survey, will be needed for a rigorous estimate of the fraction of stars in the Galactic EMR knot. Why in our Milky Way only EMR giants are confined to such a central knot remains to be explained. Remarkably, the central few kiloparsecs of the Milky Way harbor both the highest concentration of metal-poor stars (the "poor old heart") and almost all EMR stars. This highlights the stellar population diversity at the bottom of galactic potential wells.

Department/s

  • Department of Geology
  • Lund Observatory - Has been reorganised
  • eSSENCE: The e-Science Collaboration

Publishing year

2024-11-01

Language

English

Publication/Series

Astrophysical Journal

Volume

975

Issue

2

Document type

Journal article

Publisher

American Astronomical Society

Topic

  • Astronomy, Astrophysics and Cosmology

Keywords

  • Gaia (2360)
  • Galaxy chemical evolution (580)
  • Galaxy evolution (594)
  • Metallicity (1031)
  • Milky Way dynamics (1051)
  • Milky Way evolution (1052)
  • Milky Way formation (1053)

Status

Published

Project

  • Galactic Time Machine

ISBN/ISSN/Other

  • ISSN: 0004-637X