Mon. Not. R. Astron. Soc., 488, 1235-1247 (2019/September-1)
Evidence for two early accretion events that built the Milky Way stellar halo.
MYEONG G.C., VASILIEV E., IORIO G., EVANS N.W. and BELOKUROV V.
Abstract (from CDS):
The Gaia Sausage is the major accretion event that built the stellar halo of the Milky Way galaxy. Here, we provide dynamical and chemical evidence for a second substantial accretion episode, distinct from the Gaia Sausage. The Sequoia Event provided the bulk of the high-energy retrograde stars in the stellar halo, as well as the recently discovered globular cluster FSR 1758. There are up to six further globular clusters, including ω Centauri, as well as many of the retrograde substructures in Myeong et al., associated with the progenitor dwarf galaxy, named the Sequoia. The stellar mass in the Sequoia galaxy is ∼5 x 10 M☉ , whilst the total mass is ∼1010 M☉ , as judged from abundance matching or from the total sum of the globular cluster mass. Although clearly less massive than the Sausage, the Sequoia has a distinct chemodynamical signature. The strongly retrograde Sequoia stars have a typical eccentricity of ∼0.6, whereas the Sausage stars have no clear net rotation and move on predominantly radial orbits. On average, the Sequoia stars have lower metallicity by ∼0.3 dex and higher abundance ratios as compared to the Sausage. We conjecture that the Sausage and the Sequoia galaxies may have been associated and accreted at a comparable epoch.
© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
Galaxy: formation - Galaxy: halo - Galaxy: kinematics and dynamics - Galaxy: stellar content
View the reference in ADS
To bookmark this query, right click on this link: simbad:2019MNRAS.488.1235M and select 'bookmark this link' or equivalent in the popup menu