The Hercules stream as seen by APOGEE-2 South
Jason A. S. Hunt, Jo Bovy, Angeles P\'erez-Villegas, Jon A. Holtzman,, Jennifer Sobeck, Drew Chojnowski, Felipe A. Santana, Pedro A. Palicio,, Christopher Wegg, Ortwin Gerhard, Andr\'es Almeida, Dmitry Bizyaev, Jose G., Fernandez-Trincado, Richard R. Lane

TL;DR
This study detects the Hercules stream in the APOGEE-2 South data, supporting the hypothesis that it results from the outer Lindblad resonance of a fast Galactic bar, with implications for understanding the Milky Way's dynamics.
Contribution
First detection of the Hercules stream in the APOGEE-2 South data along a specific line of sight, providing evidence favoring the fast-bar (OLR) model over the slow-bar (corotation) model.
Findings
Hercules-like feature detected up to 4 kpc from the Sun.
Data matches well with the fast-bar (OLR) model predictions.
Slow-bar (corotation) model provides a poorer fit to the observed data.
Abstract
The Hercules stream is a group of co-moving 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 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 , 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…
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