Footprints of the Sagittarius dwarf galaxy in the Gaia data set

By C. Laporte, I. Minchev, K. Johnston, F. G'omez. Monthly notices of the Royal Astronomical Society, 2018

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We analyse an N-body simulation of the interaction of the Milky Way (MW) with a Sagittarius-like dSph (Sgr), looking for signatures which may be attributed to its orbital history in the phase space volume around the Sun in light of Gaia DR2 discoveries. The repeated impacts of Sgr excite coupled vertical and radial oscillations in the disc which qualitatively, and to a large degree quantitatively are able to reproduce many features in the 6D Gaia DR2 samples, from the median VR, Vϕ, V$z$ velocity maps to the local δρ($v$$z$, $z$) phase-space spiral which is a manifestation of the global disc response to coupled oscillations within a given volume. The patterns in the large-scale velocity field are well described by tightly wound spirals and vertical corrugations excited from Sgr’s impacts. We show that the last pericentric passage of Sgr resets the formation of the local present-day δρ($v$$z$, $z$) spiral and situate its formation around 500-800 Myr. As expected δρ(vz, $z$) grows in size and decreases in woundedness as a function of radius in both the Gaia DR2 data and simulations. This is the first N-body model able to explain so many of the features in the data on different scales. We demonstrate how to use the full extent of the Galactic disc to date perturbations dating from Myr to Gyr, probe the underlying potential and constrain the mass-loss history of Sgr. δρ(vz, $z$) looks the same in all stellar populations age bins down to the youngest ages which rules out a bar buckling origin.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/a81ef5bc4395939b295249f5fc4d4bc08c94f7f9

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The Spur and the Gap in GD-1: Dynamical Evidence for a Dark Substructure in the Milky Way Halo (2018, background): “Sagittarius is likely less massive (∼109− 1011 Me; Jiang & Binney 2000) but still a significant perturber in the inner Galaxy (e.g., Laporte et al. 2019a, 2019b).”
Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18 (2019, background): “…in the field of Galactic dynamics (e.g. Gaia Collaboration 2018c,d; Antoja et al. 2018; Kawata et al. 2018; Quillen et al. 2018; Ramos et al. 2018; Laporte et al. 2019; Monari et al. 2019; Trick et al. 2019), star clusters and associations (e.g. Gaia Collaboration 2018a; Cantat-Gaudin et al.…”