KINEMATIC DISCOVERY OF A STELLAR STREAM LOCATED IN PISCES

We report the kinematic discovery of the Pisces Stellar Stream (PSS), at Galactic longitude l ≈ 135° and –39° < b < –36°. We originally identified this halo substructure from velocities of red giant branch stars in the Sloan Digital Sky Survey (SDSS) Data Release 8, and confirmed its presence in turnoff stars from SDSS photometric data. The PSS is a narrow, kinematically cold tidal stream, with σv,0 ≈ 8 km s–1. Its metallicity is [Fe/H] ≈–2.2, with ∼0.3 dex dispersion. The color-magnitude signature of the stream turnoff, combined with our measured metallicity, places the PSS at a distance of 35 ± 3 kpc. The PSS is the same as the previously announced ''Triangulum stream'' and part of the proposed ''stream a''. We rule out an association of the PSS with other previously known Milky Way substructures in the same region of the sky.