Authors: Peter Erwin, J.C. Vega Beltran, Alister W. Graham & J.E. Beckman
Abstract: We present a detailed morphological, photometric, and kinematic analysis of two barred S0 galaxies with large, luminous inner disks inside their bars. We show that these structures, in addition to being geometrically disk-like, have exponential profiles (scale lengths ~ 300-500 pc) distinct from the central, non-exponential bulges. We also find them to be kinematically disk-like. The inner disk in NGC 2787 has a luminosity roughly twice that of the bulge; but in NGC 3945, the inner disk is almost ten times more luminous than the bulge, which itself is extremely small (half-light radius ~ 100 pc, in a galaxy with an outer ring of radius ~ 14 kpc) and only ~ 5% of the total luminosity — a bulge/total ratio much more typical of an Sc galaxy. We estimate that at least 20% of (barred) S0 galaxies may have similar structures, which means that their bulge/disk ratios may be significantly overestimated. These inner disks dominate the central light of their galaxies; they are at least an order of magnitude larger than typical nuclear disks found in ellipticals and early-type spirals. Consequently, they must affect the dynamics of the bars in which they reside.