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Title: A NEW STELLAR CHEMO-KINEMATIC RELATION REVEALS THE MERGER HISTORY OF THE MILKY WAY DISK

The velocity dispersions of stars near the Sun are known to increase with stellar age, but age can be difficult to determine, so a proxy like the abundance of α elements (e.g., Mg) with respect to iron, [α/Fe], is used. Here we report an unexpected behavior found in the velocity dispersion of a sample of giant stars from the Radial Velocity Experiment survey with high-quality chemical and kinematic information, in that it decreases strongly for stars with [Mg/Fe] > 0.4 dex (i.e., those that formed in the first gigayear of the Galaxy's life). These findings can be explained by perturbations from massive mergers in the early universe, which have affected the outer parts of the disk more strongly, and the subsequent radial migration of stars with cooler kinematics from the inner disk. Similar reversed trends in velocity dispersion are also found for different metallicity subpopulations. Our results suggest that the Milky Way disk merger history can be recovered by relating the observed chemo-kinematic relations to the properties of past merger events.
Authors:
; ; ; ;  [1] ;  [2] ; ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ; ;  [8] ;  [9] ;  [10] ; ;  [11] ;  [12] ;  [13] more »; « less
  1. Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany)
  2. Centre for Astrophysics and Supercomputing, Swinburne University of Technology, P.O. Box 218, Hawthorn, VIC 3122 (Australia)
  3. Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, D-69120 Heidelberg (Germany)
  4. Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana (Slovenia)
  5. Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States)
  6. Rudolf Peierls Centre for Theoretical Physics, Keble Road, Oxford OX1 3NP (United Kingdom)
  7. Sydney Institute for Astronomy, School of Physics, University of Sydney, Sydney, NSW 2006 (Australia)
  8. CNRS, Observatoire Astronomique, Université de Strasbourg, 11 rue de l'Université, F-67000 Strasbourg (France)
  9. Australian National University, Canberra, ACT 0200 (Australia)
  10. Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE (United Kingdom)
  11. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom)
  12. Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700-AV Groningen (Netherlands)
  13. Department of Astronomy, New Mexico State University, Las Cruces, NM 88003 (United States)
Publication Date:
OSTI Identifier:
22364031
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 781; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; DISTURBANCES; GIANT STARS; IRON; METALLICITY; MILKY WAY; RADIAL VELOCITY; STAR CLUSTERS; STAR EVOLUTION; SUN; UNIVERSE