Two-dimensional Decomposition of Bulge and Disk

We describe a method of bulge-to-disk decomposition which utilizes a full two-dimensional image of a galaxy. It provides much better estimates of the structural parameters for each component than the widely used conventional procedure which involves a χ2 decomposition on elliptically averaged profiles. The performances of the conventional one-dimensional method and the present two-dimensional technique are compared by using a set of realistic model galaxy images. We show that the conventional one-dimensional decomposition procedure is subject to strong systematic errors associated with the derivation of the elliptically averaged radial surface brightness profiles; these errors come from the different intrinsic shapes of disk and bulge, combined with the effects of viewing inclination. The present two-dimensional approach successfully recovers the intrinsic parameters for a wide range of B/D ratios at all inclinations.