In response to criticism by Momany et al .
( 17 ) , that the recently-identified Canis Major ( CMa ) overdensity could be simply explained by the Galactic warp , we present proof of the existence of a stellar population in the direction of CMa that can not be explained by known Galactic components .
By analyzing the radial distribution of counts of M-giant stars in this direction , we show that the ( 17 ) warp model overestimates the number of stars in the Northern hemisphere , hence hiding the CMa feature in the South .
The use of a better model of the warp has little influence on the morphology of the overdensity and clearly displays an excess of stars grouped at a distance of D = 7.2 \pm 0.3 { kpc } .
To lend further support to the existence of a population that does not belong to the Galactic disc , we present radial velocities of M-giant stars in the centre of the CMa structure that were obtained with the 2dF spectrograph at the AAT .
The extra population shows a radial velocity of v _ { r } = 109 \pm 4 { km s ^ { -1 } } , which is significantly higher than the typical velocity of the disc at the distance of CMa .
This population also has a low dispersion ( 13 \pm 4 { km s ^ { -1 } } ) .
The Canis Major overdensity is therefore highly unlikely to be due to the Galactic warp , adding weight to the hypothesis that we are observing a disrupting dwarf galaxy or its remnants .
This leads to questions on what part of CMa was previously identified as the Warp and how to possibly disentangle the two structures .