NOAO >   Observing Info >   Approved Programs >   2011A-0093

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Proposal Information for 2011A-0093


PI: David M. Nataf, The Ohio State University, nataf@astronomy-ohio-state.edu
Address: Astronomy Department, 140 W 18th Avenue, Columbus, OH 43210, USA

CoI: Andrew Gould, The Ohio State University
CoI: Jennifer Johnson, The Ohio State University
CoI: Andrzej Udalski, Warsaw University Observatory
CoI: Radosaw Poleski, Warsaw University Observatory
CoI: Lia Athanassoula, Laboratoire d'Astrophysique de Marseille

Title: Does the Milky Way Have an X-Shaped Bulge? A Dynamical Investigation

Abstract: Recent complementary findings (Nataf et al. 2010, McWilliam & Zoccali 2010) indicate that there are two red clump overdensities on sightlines toward the bulge at least 5^\circ (~700 pc) removed from the plane. The two populations are separated by ~0.5 magnitudes in brightness but have indistinguishable colors, indicating a geometric rather than age/chemical difference between the two populations, though there are some very narrow regions of evolutionary parameter-space whereby the latter explanation is possible. We wish to obtain radial velocities (RV) of these two populations to constrain their nature. If the bulge is X-shaped as suggested by McWilliam & Zoccali (2010) then the RV distribution toward those sightlines will be multimodal rather than unimodal. Combining RV measurements obtained in this study with upcoming measurements from the OGLE-III proper motion survey (Poleski et al. 2011, in preparation) will yield the first study of any Galactic spheroid to span all six dimensions of dynamical phase space. N-body simulations and orbital structure work will be used to model and interpret the data and obtain information on the X-shape.


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