Volume 615, July 2018
|Number of page(s)||7|
|Section||Galactic structure, stellar clusters and populations|
|Published online||20 July 2018|
Searching for a kinematic signature of the moderately metal-poor stars in the Milky Way bulge using N-body simulations
GEPI, Observatoire de Paris, Université PSL, CNRS,
5 Place Jules Janssen,
2 Laboratoire Lagrange, Université de la Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Bd de l’Observatoire, 06304 Nice, France
3 LERMA, Observatoire de Paris, Université PSL, CNRS, UPMC, Sorbonne Univ., 61 Av. de l′Observatoire, 75014 Paris, France
4 Collège de France, 11 Place Marcelin Berthelot, 75005 Paris, France
Accepted: 14 March 2018
Although there is consensus that metal-rich stars in the Milky Way bulge are formed via secular evolution of the thin disc, the origin of their metal-poor counterparts is still under debate. Two different origins have been invoked for metal-poor stars: they might be classical bulge stars or stars formed via internal evolution of a massive thick disc. We use N-body simulations to calculate the kinematic signature given by the difference in the mean Galactocentric radial velocity (ΔVGC) between metal-rich stars ([Fe/H] ≥ 0) and moderately metal-poor stars (–1.0 ≤ [Fe/H] < 0) in two models, one containing a thin disc and a small classical bulge (B/D = 0.1), and the other containing a thin disc and a massive centrally concentrated thick disc. We reasonably assume that thin-disk stars in each model may be considered as a proxy of metal-rich stars. Similarly, bulge stars and thick-disc stars may be considered as a proxy of metal-poor stars. We calculate ΔVGC at different latitudes (b = 0°, − 2°, − 4°, − 6°, − 8° and − 10°) and longitudes (l = 0°, ± 5°, ± 10° and ± 15°) and show that the ΔVGC trends predicted by the two models are different. We compare the predicted results with ARGOS data and APOGEE DR13 data and show that moderately metal-poor stars are well reproduced with the co-spatial stellar discs model, which has a massive thick disc. Our results give more evidence against the scenario that most of the metal-poor stars are classical bulge stars. If classical bulge stars exists, most of them probably have metallicities [Fe/H] < –1 dex, and their contribution to the mass of the bulge should be a small percentage of the total bulge mass.
Key words: methods: numerical / Galaxy: bulge / Galaxy: kinematics and dynamics / Galaxy: structure
© ESO 2018
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.