A COLD MILKY WAY STELLAR STREAM IN THE DIRECTION OF TRIANGULUM

We present evidence for a new Milky Way stellar tidal stream in the direction of the Andromeda and Triangulum (M31 and M33) galaxies. Using a matched-filter technique, we search the Sloan Digital Sky Survey Data Release 8 by creating stellar density maps which probe the Milky Way halo at distances between 8 and 40 kpc. A visual search of these maps recovers all of the major known stellar streams, as well as a new stream in the direction of M31/M33 that we name the Triangulum stream. The stream spans 0 degrees.2 by 12 degrees. on the sky, or 75 pc by 5.5 kpc in physical units with a best-fitting distance of 26 +/- 4 kpc. The width of the stream is consistent with being the tidal remnant of a globular cluster. A color-magnitude diagram of the stream region shows an overdensity which, if identified as a main-sequence turnoff, corresponds to an old (similar to 12 Gyr) and metal-poor ([Fe/H] similar to -1.0 dex) stellar population. Future kinematic studies of this and similar cold streams will provide tight constraints on the shape of the Galactic gravitational potential.