Figure 1
Schematic diagram of how a large scale bar (Main Bar) passing though a
disk can transport material towards the nucleus of the galaxy. It is
difficult for simulations to get material all the way to the center
because it tends to get trapped at the Inner Lindblad Resonance (ILR).
This figure shows the Inner Bar that may form interior to the ILR and
transport material all the way to the nucleus. In this figure, the Main
Bar rotates clockwise, while we still aren't sure exactly how the Inner
bar moves.