Disentangling the Hercules Stream

Using high-resolution spectra of nearby F and G dwarf stars, we haveinvestigated the detailed abundance and age structure of the Hercules stream.We find that the stars in the stream have a wide range of stellar ages,metallicities, and element abundances. By comparing to existing samples ofstars in the solar neighbourhood with kinematics typical of the Galactic thinand thick disks we find that the properties of the Hercules stream distinctlyseparate into the abundance and age trends of the two disks. Hence, we find itunlikely that the Hercules stream is a unique Galactic stellar population, butrather a mixture of thin and thick disk stars. This points toward a dynamicalorigin for the Hercules stream, probably caused by the Galactic bar.Comment: Accepted for publication in ApJ Letter