Stellar disks and embedded bars in early-type galaxies - I. 2-D photometric decomposition of 28 southern early-type galaxies

We present photometric disk-bulge decompositions of 28 southern early-type galaxies with types T < -3 in either the RC3 or ESO-Lauberts & Valentijn catalogues. The decomposition method applied here is based on that developed by Scorza & Bender (1995) but the improved version allows for arbitrary surface brightness profiles of the disk models. We find three types of objects in this sample: bulge-dominated systems, with fully embedded close to edge-on disks; disk-dominated close to edge-on objects and objects with barred disks being modestly inclined down to face-on. Like in Scorza & Bender (1995), the analysis made here indicates that the superposition of a thin disk and an elliptical bulge can give good account for the morphology of most of the galaxies. We find the disks to have a diversity of surface brightness profiles, the most frequent case being that of a disk with an exponential profile, which becomes steeper at small radii. After disk subtraction, the bulges follow more closely the r(1/4) law. Five of the galaxies show signatures of embedded bar components. These have flat surface brightness profiles at small radii and rectangular shape, which are typical features of barred early-type galaxies. We find that the properties of the galaxies, most notably the disk-to-total ratio, correlates only modestly with the original classification of the galaxies.