Central mass accumulation in nuclear spirals

In central regions of non-axisymmetric galaxies high-resolution hydrodynamical simulations indicate spiral shocks, which are capable of transporting gas inwards. The efficiency of transport is lower at smaller radii, therefore instead of all gas dropping onto the galactic centre, a roughly uniform distribution of high-density gas develops in the gaseous nuclear spiral downstream from the shock, and the shear in gas is very low there. These are excellent conditions for star formation. This mechanism is likely to contribute to the process of (pseudo-) bulge formation.