The Demographics of galactic bulges in the SDSS database
We present a new database of our two dimensional bulge disk decompositions for 14,233 galaxies drawn from SDSS DR12 in order to examine the properties of bulges residing in the local universe $0.005 z 0.05$ We performed decompositions in $g$ and $r$ bands by utilizing the \sc{galfit} software. The bulge colors and bulge to total ratios are found to be sensitive to the details in the decomposition technique, and hence we hereby provide full details of our method. The $g r$ colors of bulges derived are almost constantly red regardless of bulge size except for the bulges in the low bulge to total ratio galaxies $B/T_{\rm r} \lesssim 0.3$ Bulges exhibit similar scaling relations to those followed by elliptical galaxies, but the bulges in galaxies with lower bulge to total ratios clearly show a gradually larger departure in slope from the elliptical galaxy sequence. The scatters around the scaling relations are also larger for the bulges in galaxies with lower bulge to total ratios. Both the departure in slopes and larger scatters are likely originated from the presence of young stars. The bulges in galaxies with low bulge to total ratios show signs of a frosting of young stars so substantial that their luminosity weighted Balmer line ages are as small as 1\,Gyr in some cases. While bulges seem largely similar in optical properties to elliptical galaxies, they do show clear and systematic departures as a function of bulge to total ratio. The stellar properties and perhaps associated formation processes of bulges seem much more diverse than those of elliptical galaxies.