THE EVOLUTION OF FLOWS OF STELLAR MASS-LOSS IN ACTIVE GALAXIES

Gas flows in elliptical galaxies fuelled by stellar mass loss have been calculated numerically for three fiducial epochs using both King and de Vaucouleurs models of NGC 3379. Our results show that supernova heating is unable to prevent the inflow of stellar mass loss for a large proportion of the lifetime of most giant elliptical galaxies, irrespective of their detailed structure. At the present epoch, stellar mass loss flows inwards in those elliptical galaxies with mean line-of-sight velocity dispersion σ > σtr 300 km s-1. At earlier epochs the transition velocity dispersion σtr, dividing galaxies with inflow from those with total winds (σ tr), is smaller and allows less massive ellipticals to retain their stellar mass loss. Evolution in σtr is caused principally by evolution in the stellar mass loss rate. Because of the steepness of the galaxy mass function at the relevant masses, this leads to a rapid increase with redshift of the comoving density of active galaxies. Our model explains the association of nuclear activity with giant elliptical galaxies and predicts rapid comoving density evolution as observed. This work demonstrates the importance of considering the fate of stellar mass loss in elliptical galaxies. © 1981 Royal Astronomical Society.