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The oldest stars in the Milky Way (born in the first few billion years) areexpected to have a high density in the inner few kpc, spatially overlappingwith the Galactic bulge. We use spectroscopic data from the Pristine InnerGalaxy Survey (PIGS) to study the dynamical properties of ancient, metal-poorinner Galaxy stars. We compute distances using StarHorse, and orbitalproperties in a barred Galactic potential. With this paper, we release thespectroscopic AAT/PIGS catalogue (13 235 stars). We find that most PIGS starshave orbits typical for a pressure-supported population. The fraction of starsconfined to the inner Galaxy decreases with decreasing metallicity, but manyvery metal-poor stars (VMP, [Fe/H] < -2.0) stay confined (~ 60% stay within 5kpc). The azimuthal velocity v$_\phi$ also decreases between [Fe/H] = -1.0 and-2.0, but is constant for VMP stars (at ~ 40 km/s). The carbon-enhancedmetal-poor (CEMP) stars in PIGS appear to have similar orbital propertiescompared to normal VMP stars. Our results suggest a possible transition betweentwo spheroidal components - a more metal-rich, more concentrated, fasterrotating component, and a more metal-poor, more extended andslower/non-rotating component. We propose that the former may be connected topre-disc in-situ stars (or those born in large building blocks), whereas thelatter may be dominated by contributions from smaller galaxies. This is anexciting era where large metal-poor samples, such as in this work (as well asupcoming surveys, e.g., 4MOST), shed light on the earliest evolution of ourGalaxy.

The Pristine Inner Galaxy Survey (PIGS) VIII: Characterising the orbital properties of the ancient, very metal-poor inner Milky Way