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2006MNRAS.365.1309H - Mon. Not. R. Astron. Soc., 365, 1309-1323 (2006/February-1)
Pieces of the puzzle: ancient substructure in the Galactic disc.
HELMI A., NAVARRO J.F., NORDSTROM B., HOLMBERG J., ABADI M.G. and STEINMETZ M.
Abstract (from CDS):
The APL space for the Nordström catalogue exhibits a wealth of substructure, much of which can be linked to dynamical perturbations induced by spiral arms and the Galactic bar. However, our analysis also reveals a statistically significant excess of stars on orbits of common (moderate) eccentricity, analogous to the pattern expected for merger debris. Besides being dynamically peculiar, the 274 stars in these substructures have very distinct metallicity and age distributions, providing further evidence of their extragalactic provenance. It is possible to identify three coherent groups among these stars, that, in all likelihood, correspond to the remains of disrupted satellites. The most metal-rich group ([Fe/H] > -0.45dex) has 120 stars distributed into two stellar populations of ∼8Gyr (33 per cent) and ∼12Gyr (67 per cent) of age. The second group with <[Fe/H]>∼-0.6dex has 86 stars and shows evidence of three populations of 8Gyr (15 per cent), 12Gyr (36 per cent) and 16Gyr (49 per cent) of age. Finally, the third group has 68 stars, with typical metallicity around -0.8dex and a single age of ∼14Gyr. The identification of substantial amounts of debris in the Galactic disc whose origin can be traced back to more than one satellite galaxy, provides evidence of the hierarchical formation of the Milky Way.
Abstract Copyright: 2005 The Authors. Journal compilation © 2005 RAS
Journal keyword(s): Galaxy: disc - Galaxy: evolution - Galaxy: kinematics and dynamics - solar neighbourhood - Galaxies: evolution - Galaxies: formation
Simbad objects: 12
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