Effect of Infalling Matter on the Heavy Element Content of a Galaxy

Abstract

I HAVE considered¹ some of the possible implications of infall of intergalactic matter in galaxies, a process which was proposed by Oort² to explain the 21 cm observations of high velocity hydrogen “clouds” in our Galaxy. It was pointed out that infall of matter may have a number of important consequences for the structure and evolution of galaxies. In this communication I shall consider in more detail one of these possible consequences, namely the effect of continuing infall of matter on the composition of the interstellar medium and the Population I component of a galaxy. I shall show that in the presence of infalling matter the heavy element content of the interstellar material will tend to approach a constant value which is independent of both the infall rate and the early history of the galaxy, and depends only on stellar evolution processes.