Probing the Galaxy's bars via the Hercules stream

Abstract

It has been suggested that a resonance between a rotating bar and stars in the solar neighbourhood can produce the so called 'Hercules stream'. Recently, a second bar may have been identified in the Galactic centre, the so called 'long bar', which is longer and much flatter than the traditional Galactic bar, and has a similar mass. We looked at the dynamical effects of both bars, separately and together, on orbits of stars integrated backwards from local position and velocities, and a model of the Galactic potential which includes the bars directly. Both bars can produce Hercules like features, and allow us to measure the rotation rate of the bar(s). We measure a pattern speed, for both bars, of 1.87 +/- 0.02 times the local circular frequency. This is on par with previous measurements for the Galactic bar, although we do adopt a slightly different Solar motion. Finally, we identify a new kinematic feature in local velocity space, caused by the long bar, which is tempting to identify with the high velocity 'Arcturus' stream.

9 pages, 10 figures, Accepted to MNRAS, Corrected for errata

References in corpus (4)

• The Geneva-Copenhagen Survey of the Solar neighbourhood II. New uvby calibrations and rediscussion of stellar ages, the G dwarf problem, age-metallicity diagram, and heating mechanisms of the disk
• Tracing the long bar with red-clump giants
• The Long Bar in the Milky Way. Corroboration of an old hypothesis
• New Constraints on the Galactic Bar

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• Stellar Stream Candidates in the Solar Neighborhood Found in the LAMOST DR3 and TGAS
• Stellar substructures in the solar neighbourhood IV. Kinematic Group 1 in the Geneva-Copenhagen survey
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