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

    52 Citations (Scopus)

    Abstract

    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
    Volume413
    Issue number3
    DOIs
    Publication statusPublished - May 2011

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