Galactic Halo Stellar Structures in the Triangulum-Andromeda Region

This letter reports on the Galactic stellar structures that appear in theforeground of our Canada-France-Hawaii-Telecopse/MegaCam survey of the halo ofthe Andromeda galaxy. We recover the main sequence and main sequence turn-offof the Triangulum-Andromeda structure recently found by Majewski andcollaborators at a heliocentric distance of ~20 kpc. The survey also revealsanother less populated main sequence at fainter magnitudes that couldcorrespond to a more distant stellar structure at ~28 kpc. Both structures aresmoothly distributed over the ~76 sq. deg. covered by the survey although thecloser one shows an increase in density by a factor of ~2 towards theNorth-West. The discovery of a stellar structure behind theTriangulum-Andromeda structure that itself appears behind the low-latitudestream that surrounds the Galactic disk gives further evidence that the innerhalo of the Milky Way is of a spatially clumpy nature.Comment: accepted for publication in ApJL, 4 pages, 4 figures. Significant changes including a larger dataset and a more thorough discussio