The formation of a thick disk through the heating of a thin disk: Agreement with orbital eccentricities of stars in the solar neighborhood - Astrophysics > Cosmology and Nongalactic AstrophysicsReport as inadecuate




The formation of a thick disk through the heating of a thin disk: Agreement with orbital eccentricities of stars in the solar neighborhood - Astrophysics > Cosmology and Nongalactic Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: We study the distribution of orbital eccentricities of stars in thick disksgenerated by the heating of a pre-existing thin stellar disk through a minormerger mass ratio 1:10, using N-body-SPH numerical simulations ofinteractions that span a range of gas fractions in the primary disk and initialorbital configurations. The resulting eccentricity distributions have anapproximately triangular shape, with a peak at 0.2-0.35, and a relativelysmooth decline towards higher values. Stars originally in the satellite galaxytend to have higher eccentricities on average from e = 0.45 to e = 0.75,which is in general agreement with the models of Sales and collaborators,although in detail we find fewer stars with extreme values and no evidence oftheir secondary peak around e = 0.8. The absence of this high-eccentricityfeature results in a distribution that qualitatively matches the observations.Moreover, the increase in the orbital eccentricities of stars in the solarneighborhood with vertical distance from the Galactic mid-plane recently foundby Diericxk and collaborators can be qualitatively reproduced by our models,but only if the satellite is accreted onto a direct orbit. We thus speculatethat if minor mergers were the dominant means of formating the Milky Way thickdisk, the primary mechanism should be merging with satellites on directorbits.



Author: P. Di Matteo, M. D. Lehnert, Y. Qu, W. van Driel

Source: https://arxiv.org/







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