  The Sloan Digital Sky Survey has recently discovered a coherent ring of stars
at low galactic latitude that is believed to be the tidal stream of a merging
dwarf galaxy in the Galactic plane (named the Monoceros tidal stream). The
existence and location of the core of its progenitor galaxy is still
controversial. The best candidate is the Canis Major dwarf galaxy, a distinct
overdensity of red stars discovered in the 2MASS survey, but also interpreted
as the signature of the Galactic warp viewed in projection. In this paper, we
report a variety of new observational evidence that supports the notion that
CMa is the remnant of a partially disrupted core of a dwarf satellite. The
comparison of the orbit derived from our theoretical model for the parent
galaxy of this ring-like structure with an accurate determination of CMa orbit
leads to the conclusion that this satellite is the best candidate for the
progenitor of the Monoceros tidal stream.
