2018/05/01 by G. C. Myeong, N. W. Evans, V. Belokurov +2 · 1 voice · 1 citation
Physics and Astronomy · #astro-ph.CO #astro-ph.GA
paper · pdf · doi:10.3847/2041-8213/aad7f7
ApJL, revised version
arxiv published 2018/05/01 · arxiv created 2018/07/02 · arxiv updated 2018/07/02
The Gaia Sausage is an elongated structure in velocity space discovered by Belokurov et al. (2018) using the kinematics of metal-rich halo stars. It was created by a massive dwarf galaxy (∼ 5 × 1010 M_\odot) on a strongly radial orbit that merged with the Milky Way at a redshift z\lesssim 3. We search forthe associated Sausage Globular Clusters by analysing the structure of 91 Milky Way globular clusters (GCs) in action space using the Gaia Data Release 2 catalogue, complemented with Hubble Space Telescope proper motions. There is a characteristic energy E\rm crit which separates the in situ objects, such as the bulge/disc clusters, from the accreted objects, such as the young halo clusters. There are 15 old halo GCs that have E > E\rm crit. Eight of the high energy, old halo GCs are strongly clumped in azimuthal and vertical action, yet strung out like beads on a chain at extreme radial action. They are very radially anisotropic (β∼ 0.95) and move on orbits that are all highly eccentric (e \gtrsim 0.80). They also form a track in the age-metallicity plane distinct from the bulk of the Milky Way GCs and compatible with a dwarf spheroidal origin. These properties are consistent with GCs associated with the merger event that gave rise to the Gaia Sausage.