We present a detailed analysis of high-resolution , high S / N spectra for 5 Aquarius stream stars observed with the MIKE spectrograph on the Magellan Clay telescope .
Our sample represents one third of the 15 known members in the stream .
We find the stream is not mono-metallic : the metallicity ranges from [ Fe/H ] = - 0.63 to - 1.58 .
No anti-correlation in Na–O abundances is present , and we find a strong positive Mg–Al relationship , similar to that observed in the thick disk .
We find no evidence that the stream is a result of a disrupted classical globular cluster , contrary to a previously published claim .
High [ ( Na , Ni , \alpha ) /Fe ] and low [ Ba/Y ] abundance ratios in the stream suggests it is not a tidal tail from a disrupted dwarf galaxy , either .
The stream is chemically indistinguishable from Milky Way field stars with the exception of one candidate , C222531-145437 .
From its position , velocity , and detailed chemical abundances , C222531-145437 is likely a star that was tidally disrupted from \omega -Centauri .
We propose the Aquarius stream is Galactic in origin , and could be the result from a disk-satellite perturbation in the Milky Way thick disk on the order of a few Gyr ago : derived orbits , UVW velocities , and angular momenta of the Aquarius members offer qualitative support for our hypothesis .
Assuming C222531-145437 is a tidally disrupted member of \omega -Centauri , this system is the most likely disk perturber .
In the absence of compelling chemical and/or dynamical evidence that the Aquarius stream is the tidal tail of a disrupted satellite , we advocate the “ Aquarius group ” as a more appropriate description .
Like the Canis Major over-density , as well as the Hercules and Monoceros groups , the Aquarius group joins the list of kinematically-identified substructures that are not actually accreted material : they are simply part of the rich complexity of the Milky Way structure .