Testing formation mechanisms of the Milky Way's thick disc with RAVE

Michelle L. Wilson*, Amina Helmi, Heather L. Morrison, Maarten A. Breddels, O. Bienaymé, J. Binney, J. Bland-Hawthorn, R. Campbell, K. C. Freeman, J. P. Fulbright, B. K. Gibson, G. Gilmore, E. K. Grebel, U. Munari, J. F. Navarro, Q. A. Parker, W. Reid, G. Seabroke, A. Siebert, A. SivieroM. Steinmetz, M. E K Williams, R. F G Wyse, T. Zwitter

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

49 Citations (Scopus)


We study the eccentricity distribution of a thick-disc sample of stars (defined as those withVy > 50kms-1and1 < |z|/kpc < 3) observed in the Radial Velocity Experiment (RAVE). We compare this distribution with those obtained in four simulations of galaxy formation taken from the literature as compiled by Sales et al. Each simulation emphasizes different scenarios for the origin of such stars (satellite accretion, heating of a pre-existing thin disc during a merger, radial migration, and gas-rich mergers). We find that the observed distribution peaks at low eccentricities and falls off smoothly and rather steeply to high eccentricities. This finding is fairly robust to changes in distances and to plausible assumptions about thin-disc contamination. Our results favour models where the majority of stars formed in the Galaxy itself on orbits of modest eccentricity and disfavour the pure satellite accretion case. A gas-rich merger origin where most of the stars form 'in situ' appears to be the most consistent with our data.

Original languageEnglish
Pages (from-to)2235-2241
Number of pages7
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
Publication statusPublished - May 2011

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