Cordoni, GiacomoDa Costa, GaryYong, DavidMackey, DougalMarino, Anna FMonty, StephanieNordlander, ThomasNorris, JohnAsplund, MartinBessell, MikeCasey, A. R.Frebel, AnnaLind, K.Murphy, SimonSchmidt, BrianGao, X DXylakis-Dornbusch, T.Amarsi, A. M.Milone, A. P.2023-03-162023-03-160035-8711http://hdl.handle.net/1885/287127In this work, we combine spectroscopic information from the SkyMapper survey for Extremely Metal-Poor stars and astrometry from Gaia DR2 to investigate the kinematics of a sample of 475 stars with a metallicity range of -6.5 <= [Fe/H] <= -2.05 dex. Exploiting the action map, we identify 16 and 40 stars dynamically consistent with the Gaia Sausage and Gaia Sequoia accretion events, respectively. The most metal poor of these candidates have metallicities of [Fe/H] = - 3.31 and - 3.74, respectively, helping to define the low-metallicity tail of the progenitors involved in the accretion events. We also find, consistent with other studies, that similar to 21 per cent of the sample have orbits that remain confined to within 3 kpc of the Galactic plane, that is, |Z(max)| <= 3 kpc. Of particular interest is a subsample (similar to 11 per cent of the total) of low |Z(max)| stars with low eccentricities and prograde motions. The lowest metallicity of these stars has [Fe/H] = -4.30 and the subsample is best interpreted as the very low-metallicity tail of the metal-weak thick disc population. The low |Z(max)|, low eccentricity stars with retrograde orbits are likely accreted, while the low |Z(max)|, high eccentricity pro- and retrograde stars are plausibly associated with the Gaia Sausage system. We find that a small fraction of our sample (similar to 4 per cent of the total) is likely escaping from the Galaxy, and postulate that these stars have gained energy from gravitational interactions that occur when infalling dwarf galaxies are tidally disrupted.This work has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research innovation programme (grant agreement ERC-StG 2016, no. 716082 ‘GALFOR’, PI: Milone, http://progetti.dfa.unipd.it/GA LFOR). ADM is supported by an Australian Research Council Future Fellowship (FT160100206). AFM acknowledges support by the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie (grant agreement no. 797100). ARC is supported in part by the Australian Research Council through a Discovery Early Career Researcher Award (DE190100656). AMA acknowledges support from the Swedish Research Council (VR 2016-03765), and the project grant ‘The New Milky Way’ (KAW 2013.0052) from the Knut and Alice Wallenberg Foundation. Parts of this research were supported by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through project number CE170100013. APM acknowledges support from MIUR through the FARE project R164RM93XW SEMPLICE (PI: Milone) and the PRIN program 2017Z2HSMF (PI: Bedin). K.L. acknowledges funds from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 852977). AF acknowledges support from NSF grant AST-1255160.application/pdfen-AU© 2020 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Societystars: kinematics and dynamicsGalaxy: discGalaxy: formationGalaxy: haloGalaxy: kinematics and dynamicsGalaxy: structure202110.1093/mnras/staa34172022-01-09