THE MASS INFLOW RATE IN THE BARRED GALAXY NGC-1530

Mass inflow in barred galaxies has been invoked to account for a wide variety of phenomena, but until now direct evidence for inflow has bee n lacking. We present Fabry-Perot H alpha observations of the barred s piral galaxy NGC 1530, from which we determine velocities of the ioniz ed gas for the entire region swept by the bar. We compare the velocity field to models of gas flow in barred spirals and show that it is wel l reproduced by ideal gas hydrodynamic models. Inspection of the model s and observations reveals that gas entering the bar dust lanes stream s directly down the dust lanes toward the 2 kpc radius nuclear ring. T he models predict that approximately 20% of the gas flowing down the d ust lane enters the nuclear ring; the remaining gas sprays around the ring to the other bar dust lane. The fraction of the gas entering the ring is relatively insensitive to the shape or size of the bar. Our ob servations of the velocity field and dust optical depth yield a mass i nflow rate into the nuclear ring of 1 M. yr(-1).