ARE HIGH VELOCITY PEAKS IN THE MILKY WAY BULGE DUE TO THE BAR?
- Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China)
- Department of Physics and Astronomy, University of California at Los Angeles, Los Angeles, CA 90095 (United States)
- Leibniz-Institute für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany)
- Galaxy and Cosmology Division, National Astronomical Observatories of China, Chinese Academy of Sciences, A20 Datun Road, Room A505, Chaoyang District, Beijing 100012 (China)
Recently the commissioning APOGEE observations of the Galactic bulge reported that a significant fraction of stars (∼10%) are in a cold (σ{sub V} ≈ 30 km s{sup –1}) high velocity peak (Galactocentric radial velocity ≈200 km s{sup –1}). These stars are speculated to reflect the stellar orbits in the Galactic bar. In this study, we use two N-body models of a Milky Way-like disk galaxy with different bar strengths to critically examine this possibility. The general trends of the Galactocentric radial velocity distribution in observations and simulations are similar, but neither our models nor the BRAVA data reveal a statistically significant cold high velocity peak. A Monte Carlo test further suggests that it is possible for a spurious high velocity peak to appear if there are only a limited number of stars observed. Thus, the reported cold high velocity peak, even if it is real, is unlikely due to stars on the bar-supporting orbits. Our models do predict an excess of stars with high radial velocity, but not in a distinct peak. In the distance-velocity diagram, the high velocity particles in different fields exist at a similar distance ∼8.5 ± 1 kpc away from the Sun. This result may be explained by geometric intersections between the line-of-sight and the particle orbits; high velocity stars naturally exist approximately at the tangent point, without constituting a distinct peak. We further demonstrate that even without the presence of a bar structure, particle motions in an axisymmetric disk can also exhibit an excess of high velocity stars.
- OSTI ID:
- 22365912
- Journal Information:
- Astrophysical Journal Letters, Vol. 785, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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