Metallicity gradients in the Sagittarius dwarf Galaxy ( Sgr ) are investigated by using infrared photometric data from the 2MASS survey .
To search for metallicity effects , the giant branch in a field situated near the Center of the Sgr is compared to the giant branch in a field situated near its southern edge .
The contamination of Sgr giant branch by foreground Galactic stars is canceled by statistical subtraction of diagrams symmetrical in Galactic latitude .
After subtraction it is possible to reconstruct the Sgr giant branch with excellent accuracy .
The giant branch in the two fields have similar slopes but are shifted in color .
Even after correction for the differential reddening between the fields , the shift in color between the branch remains , and is very significant .
This variation in the color of the giant branch corresponds to a metallicity variation of about -0.25 Dex .
The existence of a metallicity gradient in Sgr may indicate that there are two different stellar population in Sgr .
One has low metallicity , and another one of higher metallicity has a smaller spatial extension .