The redistribution of matter in a barred spiral galaxy is primarily driven by non-axisymmetric gravitational potentials. Within the central bar, gas does not move in perfect circles. Instead, the elongated shape of the bar creates gravitational torques. These torques force the gas to lose angular momentum, causing it to spiral inward toward the galactic center. This inward migration of gas creates high density regions that fuel the nucleus.
As this gas moves through the galaxy, it interacts with the spiral arms. The bar acts as a massive engine that pushes gas into specific orbital resonances. When gas encounters the density waves of the spiral arms, it undergoes compression. This compression increases the local gas density, which triggers the gravitational collapse of molecular clouds. This process directly influences the star formation rate, as the intensified pressure in the arms makes star birth more frequent than in the quieter regions of the disk.
Essentially, the bar funnels the raw material needed for stars into the arms and the center, creating a dynamic cycle of matter redistribution and intense stellar birth.
