Residuals of the stellar mass density distribution in the disk R–Z plane, after subtracting the double-disk component fits with constant scale heights. Red arrows mark several prominent overdensity structures, namely, the Local arm (“LA”), the northern stream (“NS”), the southern stream (“SS”), and the southern clump (“SC”). “LA?” in the bottom panels indicates that the overdensity structure is suspected to be associated with the “LA” structure presented for younger populations.