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Paper: The Galactic Bulge
Volume: 491, Fifty Years of Wide Field Studies in the Southern Hemisphere: Resolved Stellar Populations in the Galactic Bulge and the Magellanic Clouds
Page: 59
Authors: Rich, R. M.
Abstract: Observations at Cerro Tololo Inter-American Observatory (CTIO) have had a critical formative impact on the study of the Galactic bulge, much of the work being inspired and supported by Victor Blanco and collaborators, which is presented in a historical overview. Recent observations at CTIO include the Blanco 4m/Hydra Bulge Radial Velocity Assay (BRAVA) that has mapped the Galactic bulge velocity field from –10<l <+10 and –10<b<–4. The velocity field shows characteristic "cylindrical" rotation that is consistent with the population being dominated by a kinematic bar that appears to have originated from the secular evolution of a massive disk. Using the Hydra multi-object spectrograph at CTIO, it has been shown that the bulge is dominated by a population that is alpha enhanced relative to the thin and thick disk, and shows the signature of the r-process being important in enrichment. Both composition indicators are consistent with early, rapid formation of the bulge. Although proper motion selected and field-subtracted color-magnitude diagrams reaching the main sequence turnoff are consistent with the bulge being predominantly globular cluster-age, analysis of microlensed dwarf stars favors a substantial fraction of the bulge being younger than 5 Gyr. To help define the overall picture of the bulge better, the Blanco DECam Bulge Survey (BDBS) will produce a multicolor ugrizY map of the bulge from –10< l<+10 and –10<b<–2 that will map the substructures as a function of metallicity and explore the spatial distribution of stars as a function of age and metallicity.
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