The photometric estimate of the metallicity and the age of the Azzopardi et al .
( [ 1991 ] ) carbon stars ( Ng [ 1997 ] ) is revised to respectively Z \simeq 0.004 and \sim 0.1 Gyr .
Under the hypothesis that the carbon stars are located at a distance related to the Sagittarius dwarf galaxy , the broad velocity dispersion of the stars can only be explained if they were formed out of Galactic material during a recent crossing of the Sagittarius dwarf galaxy through the Galactic plane .