Stellar streams are found throughout the galactic halos of the Milky Way, Andromeda and other nearby massive galaxies. They are presumed to originate from disrupting dwarf galaxies or globular clusters, providing irrefutable evidence that galaxies are formed, at least in part, hierarchically. Furthermore, their orbits can be used to constrain the shape of galactic potentials at a range of distances. Most Galactic streams have been discovered in the Sloan Digital Sky Survey (SDSS), e.g. Monoceros stream, GD-1 and Orphan stream.
For the first time, we searched both northern and southern Galactic hemisphere coverage of the SDSS for cold stellar streams. Matched filtering technique was used to filter out most of the Milky Way foreground stars. We found a new cold stellar stream in the direction of Triangulum. The stream signal is strongest at 26 kpc. It is very linear and narrow, spanning 0.2 deg by 12 deg. A color magnitude diagram of the stream region shows an overdensity which, if identified as a main sequence turn-off, corresponds to an old and metal-poor stellar population. Kinematic studies of this and similar streams will provide tight constraints on the strength, shape and lumpiness of the Galactic gravitational potential.
A Cold Milky Way Stellar Stream in the Direction of Triangulum (ADS | arXiv)
Bonaca, A., Geha, M., and Kallivayalil, N., 2012, ApJ, 760, L6