The Hercules stream as seen by APOGEE-2 South

Abstract The Hercules stream is a group of comoving stars in the solar neighbourhood, which can potentially be explained as a signature of either the outer Lindblad resonance (OLR) of a fast Galactic bar or the corotation resonance (CR) of a slower bar. In either case, the feature should be present...

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Published in:Monthly notices of the Royal Astronomical Society 2018-02, Vol.474 (1), p.95-101
Main Authors: Hunt, Jason A. S., Bovy, Jo, Pérez-Villegas, Angeles, Holtzman, Jon A., Sobeck, Jennifer, Chojnowski, Drew, Santana, Felipe A., Palicio, Pedro A., Wegg, Christopher, Gerhard, Ortwin, Almeida, Andrés, Bizyaev, Dmitry, Fernandez-Trincado, Jose G., Lane, Richard R., Longa-Peña, Penélope, Majewski, Steven R., Pan, Kaike, Roman-Lopes, Alexandre
Format: Article
Language:English
Subjects:
Astrophysics
Corotation
Lindblad resonance
Line of sight
Physics
Resonance
Solar neighborhood
Velocity distribution
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Summary:Abstract The Hercules stream is a group of comoving stars in the solar neighbourhood, which can potentially be explained as a signature of either the outer Lindblad resonance (OLR) of a fast Galactic bar or the corotation resonance (CR) of a slower bar. In either case, the feature should be present over a large area of the disc. With the recent commissioning of the APOGEE-2 Southern spectrograph we can search for the Hercules stream at (l, b) = (270°, 0), a direction in which the Hercules stream, if caused by the bar's OLR, would be strong enough to be detected using only the line-of-sight velocities. We clearly detect a narrow, Hercules-like feature in the data that can be traced from the solar neighbourhood to a distance of about 4 kpc. The detected feature matches well the line-of-sight velocity distribution from the fast-bar (OLR) model. Confronting the data with a model where the Hercules stream is caused by the CR of a slower bar leads to a poorer match, as the corotation model does not predict clearly separated modes, possibly because the slow-bar model is too hot.
ISSN:0035-8711
1365-2966
DOI:10.1093/mnras/stx2777