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  • The Pristine Inner Galaxy S...
    Arentsen, A; Starkenburg, E; Martin, N F; Hill, V; Ibata, R; Kunder, A; Schultheis, M; Venn, K A; Zucker, D B; Aguado, D; Carlberg, R; González Hernández, J I; Lardo, C; Longeard, N; Malhan, K; Navarro, J F; Sánchez-Janssen, R; Sestito, F; Thomas, G; Youakim, K; Lewis, G F; Simpson, J D; Wan, Z

    Monthly notices of the Royal Astronomical Society, 01/2020, Letnik: 491, Številka: 1
    Journal Article

    ABSTRACT Our Galaxy is known to contain a central boxy/peanut-shaped bulge, yet the importance of a classical, pressure-supported component within the central part of the Milky Way is still being debated. It should be most visible at low metallicity, a regime that has not yet been studied in detail. Using metallicity-sensitive narrow-band photometry, the Pristine Inner Galaxy Survey (PIGS) has collected a large sample of metal-poor ($\rm {Fe/H}\, \lt -1.0$) stars in the inner Galaxy to address this open question. We use PIGS to trace the metal-poor inner Galaxy kinematics as function of metallicity for the first time. We find that the rotational signal decreases with decreasing Fe/H , until it becomes negligible for the most metal-poor stars. Additionally, the velocity dispersion increases with decreasing metallicity for $-3.0 \lt \rm {Fe/H}\, \lt -0.5$, with a gradient of −44 ± 4 km s−1 dex−1. These observations may signal a transition between Galactic components of different metallicities and kinematics, a different mapping on to the boxy/peanut-shaped bulge for former disc stars of different metallicities and/or the secular dynamical and gravitational influence of the bar on the pressure-supported component. Our results provide strong constraints on models that attempt to explain the properties of the inner Galaxy.