We investigated the formation of the Hercules stream in the model Galactic disk that includes the outer elliptical rings R₁ and R₂ located near the Outer Lindblad Resonance (OLR) of the bar. Most stars in the Hercules region have orbits elongated perpendicular to the bar and support the outer ring R₁ while those in the anti-Hercules region have orbits elongated parallel to the bar and support the R₂ ring. Stars of the Gaia DR3 catalog located in the Hercules region are more strongly concentrated toward the Galactic plane than stars of the anti-Hercules region, which prevents comparison between their physical characteristics, since selection effects affect these samples differently.
Melnik et al. (Mon,) studied this question.
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